Random High Idle / Sticking Idle - <master thread>
- Thread starter Jerry Dobson
- Start date
PhoenixGTS
Enthusiast
Re: Random High Idle / Sticking Idle - <master thread>
Alright. I spent a lot of time this weekend investigating the return of idle hang when I installed a WCV-tuned PCM. With the WCV unit installed, I tweaked the throttle body adjustment every which way but loose. Driver's leading by a large amount to passenger leading by a small amount. The traditional driver's side leading by an almost inmperceptible amount leads to the smoothest low speed running. At parking garage speed, bucks when very cold, smooth when warm.
Nothing I did put a dent in the hellish idle hang exhibited by the WCV PCM. Hung at 1,700 until at least a second after coming to a complete stop. Hard driving vs. slow driving had no effect. Worst idle hang my car has ever had.
Re-installed my Mopar performance PCM and idle hang is completely gone. Not a hint of hang.
I'm sorry Gerald, but this is a software problem. It might be aggravated by hardware considerations, but this is a software problem. Sad thing is that the car is absolutely faster with a smoother power band with the WCV unit installed, but no way am I living with idle hange ever again. Next step for me is to see if maybe the WCV guys can flash there unit with the Mopar idle related routines so I can get the best of both worlds.
Alright. I spent a lot of time this weekend investigating the return of idle hang when I installed a WCV-tuned PCM. With the WCV unit installed, I tweaked the throttle body adjustment every which way but loose. Driver's leading by a large amount to passenger leading by a small amount. The traditional driver's side leading by an almost inmperceptible amount leads to the smoothest low speed running. At parking garage speed, bucks when very cold, smooth when warm.
Nothing I did put a dent in the hellish idle hang exhibited by the WCV PCM. Hung at 1,700 until at least a second after coming to a complete stop. Hard driving vs. slow driving had no effect. Worst idle hang my car has ever had.
Re-installed my Mopar performance PCM and idle hang is completely gone. Not a hint of hang.
I'm sorry Gerald, but this is a software problem. It might be aggravated by hardware considerations, but this is a software problem. Sad thing is that the car is absolutely faster with a smoother power band with the WCV unit installed, but no way am I living with idle hange ever again. Next step for me is to see if maybe the WCV guys can flash there unit with the Mopar idle related routines so I can get the best of both worlds.
94RT10Ohio
Enthusiast
Re: Random High Idle / Sticking Idle - <master thread>
If you listen to my exhaust clips you will note that my car seems to have the same issue. Bad part is not sure if it was there prior to the mods listed below, I never drove it before mods
My mods do not touch any computer items. I would think it is a mechanical issue, that can be emphasied by changing the computer.
I am going to give the spring thing a go, will let you know the results.
If you listen to my exhaust clips you will note that my car seems to have the same issue. Bad part is not sure if it was there prior to the mods listed below, I never drove it before mods
My mods do not touch any computer items. I would think it is a mechanical issue, that can be emphasied by changing the computer.I am going to give the spring thing a go, will let you know the results.
BadVenm
Enthusiast
Re: Random High Idle / Sticking Idle - <master thread>
I have fought this problem, as noted in my post on page one of this thread.
I had a noticeable idle hang on one of my daily drivers, a 2003 Ford Taurus. I bought it used to beat around in when I'm not in my truck. Since I bought it used, I assumed it was bone stock.
I opened the air box and it had a K&N filter in it. It was pretty dirty. I bought a stock paper filter and installed it. Now the idle hang is gone. Go figure.
I haven't tried that yet with my Viper, it does have K&N's. I have been using the IAC plug with a small hole trick. But that is not a fix, sometimes it solves the hang really well. Then sometimes instead of hang it idles down so low it dies at the stop light. Weird.
On the Viper I've tried the t-bodies adjustments, clearing the PCM, and all the fixes mentioned in this thread,but nothing. (I haven't tried taking out the K&N's yet)
After owning three different Vipers, I've noticed that none of them ever had hang when bone stock. Only after modifications did I ever get idle hang.
I know some fixes have fixed it for some cars, but apparently there is not a single one fix that fixes it for every car.
Keep up all the input, someone will stumble across a fix that works for every single car.
Hey Jerry Dobson, thread originator, have you taken a photo of your real cars so you can take the fake photo off of your avatar? Your lift should have your Viper and your 115,000 mile ****** grand prix on it! Not your Viper and Joe's Lotus. You POSER Maximums! Is that the same photo you use to pick up the jr. high school girls at the Ice Cream shop?
I have fought this problem, as noted in my post on page one of this thread.
I had a noticeable idle hang on one of my daily drivers, a 2003 Ford Taurus. I bought it used to beat around in when I'm not in my truck. Since I bought it used, I assumed it was bone stock.
I opened the air box and it had a K&N filter in it. It was pretty dirty. I bought a stock paper filter and installed it. Now the idle hang is gone. Go figure.
I haven't tried that yet with my Viper, it does have K&N's. I have been using the IAC plug with a small hole trick. But that is not a fix, sometimes it solves the hang really well. Then sometimes instead of hang it idles down so low it dies at the stop light. Weird.
On the Viper I've tried the t-bodies adjustments, clearing the PCM, and all the fixes mentioned in this thread,but nothing. (I haven't tried taking out the K&N's yet)
After owning three different Vipers, I've noticed that none of them ever had hang when bone stock. Only after modifications did I ever get idle hang.
I know some fixes have fixed it for some cars, but apparently there is not a single one fix that fixes it for every car.
Keep up all the input, someone will stumble across a fix that works for every single car.
Hey Jerry Dobson, thread originator, have you taken a photo of your real cars so you can take the fake photo off of your avatar? Your lift should have your Viper and your 115,000 mile ****** grand prix on it! Not your Viper and Joe's Lotus. You POSER Maximums! Is that the same photo you use to pick up the jr. high school girls at the Ice Cream shop?
PhoenixGTS
Enthusiast
Re: Random High Idle / Sticking Idle - <master thread>
More fuel for the idle hang fire. Despite Gerald's potestations, I am convinced that this is a software issue triggered by a hardware situation. Now someone who knows more about Vipers than I ever will has verified this theory. I have no Idle hang with my Mopar Performance PCM. I installed a WCV tuned PCM I bought used and have horrible hang. In an effort to address the new hang issue I talked to John at WCV for awhile today (he is super-Viper tech BTW) and he is of the mind that idle hang is greatly influenced by throttle body synchronization. I told him about how I adjusted the t-bodies and went for test drives. He pointed out that I was following a faulty procedure: 1) the throttle bodies cannot be synch'd manually , only electronically using what I believe he called a DRB diagnostic procedure that uses the available electronic sensors to determine the amount of air making it past the t-body blades at idle; and 2) each time you make an adjustment, you have to de-power the PCM for a full ten minutes before you re-test drive so that it will take a brand new look at the re-synch'd t-bodies and make its idle hang decisions from the new baseline.
I will try getting lucky with the t-body synch on my own this week and report, but I wanted to post to let folks know that a great Viper tech says that the previous recommendations I has made to the forum about manually synching the t-body is bunk. In any event, on Firday night it is the Mopar Perf PCM vs. the WCV 91 octane PCM on the dyno.
More fuel for the idle hang fire. Despite Gerald's potestations, I am convinced that this is a software issue triggered by a hardware situation. Now someone who knows more about Vipers than I ever will has verified this theory. I have no Idle hang with my Mopar Performance PCM. I installed a WCV tuned PCM I bought used and have horrible hang. In an effort to address the new hang issue I talked to John at WCV for awhile today (he is super-Viper tech BTW) and he is of the mind that idle hang is greatly influenced by throttle body synchronization. I told him about how I adjusted the t-bodies and went for test drives. He pointed out that I was following a faulty procedure: 1) the throttle bodies cannot be synch'd manually , only electronically using what I believe he called a DRB diagnostic procedure that uses the available electronic sensors to determine the amount of air making it past the t-body blades at idle; and 2) each time you make an adjustment, you have to de-power the PCM for a full ten minutes before you re-test drive so that it will take a brand new look at the re-synch'd t-bodies and make its idle hang decisions from the new baseline.
I will try getting lucky with the t-body synch on my own this week and report, but I wanted to post to let folks know that a great Viper tech says that the previous recommendations I has made to the forum about manually synching the t-body is bunk. In any event, on Firday night it is the Mopar Perf PCM vs. the WCV 91 octane PCM on the dyno.
Mike Adams
Enthusiast
Re: Random High Idle / Sticking Idle - <master thread>
Try cleaning your Air intake temperature sensor with electical contact cleaner. For the mopar to stop haning idle it has to be ignoring some reading that a stock computer is getting. I cannot be mechanical or it would not matter which computer you have.
Try cleaning your Air intake temperature sensor with electical contact cleaner. For the mopar to stop haning idle it has to be ignoring some reading that a stock computer is getting. I cannot be mechanical or it would not matter which computer you have.
AJT
Enthusiast
Re: Random High Idle / Sticking Idle - <master thread>
I borrowed a computer from Doug when he got mine reprogrammed. Idle hang went away. I got mine back & the RPM's go down to 0 & the car almost dies. I realize the PCM does this when it is learning, but it has been almost 1,000 miles. We are trying to figure this out but nothing mechanical has been adjusted on the car between the 2 computers.
First (mine) PCM had idle hang after Mods, second PCM(borrowed while mine was being reprogrammed) worked perfect for 800 miles, third PCM ( mine after reprogramming) having opposite problem RPMs go to 0 & almost die at lights.
I am no mechanic but I believe this is PCM controlled problem.
my .02
Andy
I borrowed a computer from Doug when he got mine reprogrammed. Idle hang went away. I got mine back & the RPM's go down to 0 & the car almost dies. I realize the PCM does this when it is learning, but it has been almost 1,000 miles. We are trying to figure this out but nothing mechanical has been adjusted on the car between the 2 computers.
First (mine) PCM had idle hang after Mods, second PCM(borrowed while mine was being reprogrammed) worked perfect for 800 miles, third PCM ( mine after reprogramming) having opposite problem RPMs go to 0 & almost die at lights.
I am no mechanic but I believe this is PCM controlled problem.
my .02
Andy
Falconeer
Enthusiast
1) At what outside temperature does the problem occur?
2) What year is your car?
3) Is your car BONE stock with this problem?
4) Do you have K&N filters and smooth tubes?
5) Do you have Headers installed and if so what brand?
6) What other modifications do you have that might have triggered this problem?
7) What steps have you taken to attempt to cure the problem?
1) At any temperature range
2) 1998 GTS
3) Yes
4) Yes
5) No (not totally sure about this)
6) None
7) Cleaned throttle bodies, replaced the AIS motor
Problem only occur when pressing the clutch in and running in idle. Then it sometimes idle at 2100 RPM. Though when comming to a full stop the idle automatically goes down to normal 700 RPM.. weird!!
2) What year is your car?
3) Is your car BONE stock with this problem?
4) Do you have K&N filters and smooth tubes?
5) Do you have Headers installed and if so what brand?
6) What other modifications do you have that might have triggered this problem?
7) What steps have you taken to attempt to cure the problem?
1) At any temperature range
2) 1998 GTS
3) Yes
4) Yes
5) No (not totally sure about this)
6) None
7) Cleaned throttle bodies, replaced the AIS motor
Problem only occur when pressing the clutch in and running in idle. Then it sometimes idle at 2100 RPM. Though when comming to a full stop the idle automatically goes down to normal 700 RPM.. weird!!
Falconeer
Enthusiast
What is the sequel to this story?!?Gerald: today I am going to be fiddling with and fine tuning the throttle-body synchronization. Hopefully, I will be able to back you up by showing that getting the t-bodies dialed in will not send whatever magic signal that is causing the PCM to hang the idle. Cross your fingers. It might be possible that the WCV PCM is simply more sensitive to whatever the problem is that a slightly un-synch'd t-body situation caused my old PCM to hang, but if I cannot get it, that I changed no hardware and the PCM change itself brought back a hang indicates a software issue. The PCM isn't hardware after all.It's not software.
PhoenixGTS
Enthusiast
It is definitely a software issue triggered by hardware parameters, but I never had the DRB #4 test done as requested by WCV so I could never post the outcome of that. FWIW, my local tech does not think the #4 test would do anything, but sold me a new IAC motor as a sure cure. Guess what? The WCV PCM still hangs (gee another $100 and no cure - welcome to Viperville) so I have the Mopar unit in. No hang at all because the Mopar unit ignores whatever causes the hang (and other stuff which is why it pulls less codes than other PCMS). Just like most Viper questions, Everyone has an opinion, but nobody has a solution.What is the sequel to this story?!?
AJT
Enthusiast
600 miles & no idle hang problems anymore.
davem
Enthusiast
Hello,
If you are supercharged and the throttle cable fix does not help, here's another thing that has worked well for me on 2 Roe SC vipers.
If you have the Vec 2 software you can pull fuel on the load map at high vacuum (-10 to -30). You may have to experiment a little to find the right value for you (this value is injector on time reduction in ms). This seems to eliminate the idle hang very nicely and permanently (for 2 years now on 1 car in particular). This is probably an electronic band-aid, but it is very effective.
Good luck,
Dave.
If you are supercharged and the throttle cable fix does not help, here's another thing that has worked well for me on 2 Roe SC vipers.
If you have the Vec 2 software you can pull fuel on the load map at high vacuum (-10 to -30). You may have to experiment a little to find the right value for you (this value is injector on time reduction in ms). This seems to eliminate the idle hang very nicely and permanently (for 2 years now on 1 car in particular). This is probably an electronic band-aid, but it is very effective.
Good luck,
Dave.
Go Fast For Life
Enthusiast
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Did we ever come to a decision as to the root cause of the problem? PhoenixGTS? Gerald?
Jerry Dobson
Enthusiast
Just remember with all testing that when you swapped the PCM, you have disconnected the power and reset the unit. Many of us can eliminate the idle hang by doing a PCM battery disconnect. All evaluation should include a few hundred miles.
I long time ago, I had my PCM replaced for another reason. I can not confirm, but I strongly feel that the idle hang appeared after the PCM swap.
The reason that I ask “Do you have aftermarket headers” is the location of the O2 sensor. Long tube headers have the 02 sensor further down on the pipe. Is this location potentially affecting the Air Fuel mixture? Reading less fuel, is the PCM slightly increasing the mixture and causing a slight idle increase?
My idle is so erratic. I can go for six months with virtually no problems then it will come back. When it does, it is a little dangerous. You let off the gas and the RPMs stay up. The problem is back again.
I will pull out my DRB and start to monitor the sensors and keep a log. I know I will need to reset my PCM to get a neutral starting point.
FYI: Whenever you reset your PCM, it is best to turn the ignition to the ON position, then give it full throttle twice. This will teach the PCM the full throw of the TPS.
I am on a mission!
I long time ago, I had my PCM replaced for another reason. I can not confirm, but I strongly feel that the idle hang appeared after the PCM swap.
The reason that I ask “Do you have aftermarket headers” is the location of the O2 sensor. Long tube headers have the 02 sensor further down on the pipe. Is this location potentially affecting the Air Fuel mixture? Reading less fuel, is the PCM slightly increasing the mixture and causing a slight idle increase?
My idle is so erratic. I can go for six months with virtually no problems then it will come back. When it does, it is a little dangerous. You let off the gas and the RPMs stay up. The problem is back again.
I will pull out my DRB and start to monitor the sensors and keep a log. I know I will need to reset my PCM to get a neutral starting point.
FYI: Whenever you reset your PCM, it is best to turn the ignition to the ON position, then give it full throttle twice. This will teach the PCM the full throw of the TPS.
I am on a mission!
AG98RT10
Viper Owner
My only experience with idle hang:
Last summer, first really hot days, driving around in town, I saw temps climbing up a bit and idle started hanging up around 1500 rpm. Drove out the congested area and it still was hanging, parked, went in and ate lunch, came back out and car, having cooled down some ran more normal. All this time, my AC was low on freon since the compressor seals were shot. I bought a freon kit and tried to home-charge it, but the problem persisted (since the leak wasn't fixed). Why am I providing all this info on the AC? Because that was what was causing the idle hang, as well as the cooling fan not operating correctly.
Solution for me: took the car to "real" AC repair service shop, who traced and found the leaks at the compressor seals (both), and professionally charged the system after repairing. KNOCK ON WOOD, my AC is still cold this summer, and idle hang has never once reared its ugly head since.
My experience indicates the CPU picks up a lot of data and gets confused by it sometimes. If the AC system pressures are out of whack, the CPU gets majorly confused. When my pressures went low, for example, I couldn't get the fan to turn on by turning AC on. With system properly charged, cooling fan ALWAYS turns on when I switch AC on, even on a completely cold start in the winter.
This gives me a little advantage when I see temps starting to rise a little over 190 or so in that I can "manually" lower them by turning AC on, even in winter. I also use this feature while idling in the pit area waiting to go out on the track, so I won't have to start out with temps at 200 plus degrees. (If you wait for the temp setting to trigger the fan, the engine gets a little heat soaked, so I head it off.)
Anyway, a long-winded story, but I think my only experience of idle-hang was related to the AC pressure being wrong and the CPU not turning on the fan when I switched on Compressor last year. That threw the whole thing for a loop, temps went to about 225 or 230, and idle hang came in.
So, if you've had idle hang, check out your AC - those seals are notorious for failing. And if you've "fixed" your AC and found your idle hang went away, join this club of one!
Last summer, first really hot days, driving around in town, I saw temps climbing up a bit and idle started hanging up around 1500 rpm. Drove out the congested area and it still was hanging, parked, went in and ate lunch, came back out and car, having cooled down some ran more normal. All this time, my AC was low on freon since the compressor seals were shot. I bought a freon kit and tried to home-charge it, but the problem persisted (since the leak wasn't fixed). Why am I providing all this info on the AC? Because that was what was causing the idle hang, as well as the cooling fan not operating correctly.
Solution for me: took the car to "real" AC repair service shop, who traced and found the leaks at the compressor seals (both), and professionally charged the system after repairing. KNOCK ON WOOD, my AC is still cold this summer, and idle hang has never once reared its ugly head since.
My experience indicates the CPU picks up a lot of data and gets confused by it sometimes. If the AC system pressures are out of whack, the CPU gets majorly confused. When my pressures went low, for example, I couldn't get the fan to turn on by turning AC on. With system properly charged, cooling fan ALWAYS turns on when I switch AC on, even on a completely cold start in the winter.
This gives me a little advantage when I see temps starting to rise a little over 190 or so in that I can "manually" lower them by turning AC on, even in winter. I also use this feature while idling in the pit area waiting to go out on the track, so I won't have to start out with temps at 200 plus degrees. (If you wait for the temp setting to trigger the fan, the engine gets a little heat soaked, so I head it off.)
Anyway, a long-winded story, but I think my only experience of idle-hang was related to the AC pressure being wrong and the CPU not turning on the fan when I switched on Compressor last year. That threw the whole thing for a loop, temps went to about 225 or 230, and idle hang came in.
So, if you've had idle hang, check out your AC - those seals are notorious for failing. And if you've "fixed" your AC and found your idle hang went away, join this club of one!
Jeff-00-ACR
Enthusiast
My stock 2000 ACR idles fast when the car is rolling more than about 10 miles per hour. I've noticed this from the very beginning. As I come to a stop sign or stop light, I can put the clutch in and my Viper idles around 1200 until the car drops below about 10 mph, then it drops to normal idle. Always...
Jerry Dobson
Enthusiast
Update:
This Friday I am:
1) Flashing my PCM firmware.
2) Installing new TPS
3) Installing new IAC
4) Installing new Throttle Cable / Checking all mechanicals
I will do them in stages and hope to find a solution. I still think it is computer related.
This Friday I am:
1) Flashing my PCM firmware.
2) Installing new TPS
3) Installing new IAC
4) Installing new Throttle Cable / Checking all mechanicals
I will do them in stages and hope to find a solution. I still think it is computer related.
Falconeer
Enthusiast
I had the idle hang badly for half a year.. My tech tried everything from changing the AIS motor, resetting the PCM, cleaning the throttle bodies and nothing helped. Until two months ago!!
They found out that the throttle bodies where out of sync which was a mistake from their side when they did the first repairs on my car. Half a year of suffering just to find out it was something simple like that, which THEY had caused!
But now I'm so happy with the normal idle that I don't care.. I just enjoy every ride more and more knowing how bad it had been and how perfect it runs now! It is over 500 miles ago so I must say that the problem is fixed..
Erik
They found out that the throttle bodies where out of sync which was a mistake from their side when they did the first repairs on my car. Half a year of suffering just to find out it was something simple like that, which THEY had caused!
But now I'm so happy with the normal idle that I don't care.. I just enjoy every ride more and more knowing how bad it had been and how perfect it runs now! It is over 500 miles ago so I must say that the problem is fixed..
Erik
IEATVETS
Enthusiast
Re: Random High Idle / Sticking Idle - <master thread>
This thread keeps coming up as does the Vipair and chicks thread but it has happened to me as well. My idle has begun sticking at around 1700rpm's. Eventually it does come down to normal idle but how embarrassing. Some of you say to synch the TB's. Some say to replace the throttle cables. Yet others say to reprogram the computer. Well I will throw something new into the mix. How's about a loose or disconnected vaccumm hose? I am taking my car in next Monday to have some work done and that is one of the possibilites that I was told as well. Was told it can be fixed but if it costs a lot of money I will put it in as warranty work. Will keep you posted as to what they find out.
This thread keeps coming up as does the Vipair and chicks thread but it has happened to me as well. My idle has begun sticking at around 1700rpm's. Eventually it does come down to normal idle but how embarrassing. Some of you say to synch the TB's. Some say to replace the throttle cables. Yet others say to reprogram the computer. Well I will throw something new into the mix. How's about a loose or disconnected vaccumm hose? I am taking my car in next Monday to have some work done and that is one of the possibilites that I was told as well. Was told it can be fixed but if it costs a lot of money I will put it in as warranty work. Will keep you posted as to what they find out.
Jerry Dobson
Enthusiast
Re: Random High Idle / Sticking Idle - <master thread>
Jack B is correct, vacuum leak would be constant. My problem would come and go. That is the reason I never suspect a mechanical problem.
A sticking throttle cable is easy to diagnose. Just push on the linkage and see if the idle drops. My does not.
So here is what I have done so far:
-I replaced the IAC Valve
-I replaced the TPS
I had to reset my PCM to read the new value of the TPS.
I have only driving for one day, but so far so good. I am waiting to see if it comes back.
Anytime you reset the PCM, the problem goes away, but will come back. This is the reason many misdiagnosed the fix with a "Battery Replacement". They did a temporary fix by resetting the PCM.
I noticed for my year...1998, there are three PCM flashes. If my problem is not fixed, I might look into some of the earlier software.
Jack B is correct, vacuum leak would be constant. My problem would come and go. That is the reason I never suspect a mechanical problem.
A sticking throttle cable is easy to diagnose. Just push on the linkage and see if the idle drops. My does not.
So here is what I have done so far:
-I replaced the IAC Valve
-I replaced the TPS
I had to reset my PCM to read the new value of the TPS.
I have only driving for one day, but so far so good. I am waiting to see if it comes back.
Anytime you reset the PCM, the problem goes away, but will come back. This is the reason many misdiagnosed the fix with a "Battery Replacement". They did a temporary fix by resetting the PCM.
I noticed for my year...1998, there are three PCM flashes. If my problem is not fixed, I might look into some of the earlier software.
Jerry Dobson
Enthusiast
Re: Random High Idle / Sticking Idle - <master thread>
IAC and TPS did NOT fix the problem.
I took one Viper Tech for three laps around the KS Speedway. Came into the pits and the idle was stuck at 1200 RPM.
I went back out on the Speedway with another tech. Three laps...into the pits and the idle hang was gone. It did not hang for one week after the problem. It would "float" around a small amount down low.
The tech did some research and found others finding intermitant vacum leaks caused by cracks in vacuum hoses.
Now I will post my latest findings.
IAC and TPS did NOT fix the problem.
I took one Viper Tech for three laps around the KS Speedway. Came into the pits and the idle was stuck at 1200 RPM.
I went back out on the Speedway with another tech. Three laps...into the pits and the idle hang was gone. It did not hang for one week after the problem. It would "float" around a small amount down low.
The tech did some research and found others finding intermitant vacum leaks caused by cracks in vacuum hoses.
Now I will post my latest findings.
Jerry Dobson
Enthusiast
Re: Random High Idle / Sticking Idle - <master thread>
There was another post about Air Conditioning problems.
The issue was that vacuum was being lost from the manifold from a “one way” check valve in the dash ventilation system. This would cause the dash vents to close during acceleration from loss of engine vacuum. What would be the chance of this causing a high idle?
I installed the $4.80 check valve. So far it has been over a week and the high idle is gone. The minor idle floating around is gone.
I will monitor the problem and post an update.
There was another post about Air Conditioning problems.
The issue was that vacuum was being lost from the manifold from a “one way” check valve in the dash ventilation system. This would cause the dash vents to close during acceleration from loss of engine vacuum. What would be the chance of this causing a high idle?
I installed the $4.80 check valve. So far it has been over a week and the high idle is gone. The minor idle floating around is gone.
I will monitor the problem and post an update.
SYNFULL
Enthusiast
Re: Random High Idle / Sticking Idle - <master thread>
Just wondering Jerry, if the vacuum check valve fixed the problem. Is this the same check valve used to cure the loss of air conditioning when accelerating problem?
Thanks
Gary
Just wondering Jerry, if the vacuum check valve fixed the problem. Is this the same check valve used to cure the loss of air conditioning when accelerating problem?
Thanks
Gary
SYNFULL
Enthusiast
Re: Random High Idle / Sticking Idle - <master thread>
Please answer these questions if you have the problem
1) At what outside temperature does the problem occur?
I have only had the car in the summer but it doesn't happen until the coolant gets hot.
2) What year is your car?
99 GTS ACR
3) Is your car BONE stock with this problem?
No- Didn't have it when car was stock. Installed Belanger Headers, removed cats, randomtech exaust, vec 2
4) Do you have K&N filters and smooth tubes?
Yes-
5) Do you have Headers installed and if so what brand?
Belanger
6) What other modifications do you have that might have triggered this problem?
Two things happened at a the same time and that is when it it started- fan wire burnt out and car overheated.
Cleaned and oiled k&n filters.
7) What steps have you taken to attempt to cure the problem?
Removed filters and cleaned air temp gauge with electronic cleaner. Removed iac and cleaned.
Please answer these questions if you have the problem
1) At what outside temperature does the problem occur?
I have only had the car in the summer but it doesn't happen until the coolant gets hot.
2) What year is your car?
99 GTS ACR
3) Is your car BONE stock with this problem?
No- Didn't have it when car was stock. Installed Belanger Headers, removed cats, randomtech exaust, vec 2
4) Do you have K&N filters and smooth tubes?
Yes-
5) Do you have Headers installed and if so what brand?
Belanger
6) What other modifications do you have that might have triggered this problem?
Two things happened at a the same time and that is when it it started- fan wire burnt out and car overheated.
Cleaned and oiled k&n filters.
7) What steps have you taken to attempt to cure the problem?
Removed filters and cleaned air temp gauge with electronic cleaner. Removed iac and cleaned.
vprtech
Enthusiast
Re: Random High Idle / Sticking Idle - <master thread>
I’m going to chime in here, because I think I might be able to help out with this. From my experience fixing many Vipers idle hang, there seems to be two main causes.
The first, and most common cause, is a slight shift in the closed throttle minimum tps voltage. The pcm learns this voltage after a battery reset. If, while the car is running, the voltage goes lower that what it learned at key on, it has the ability to “re-learn” the minimum position. It cannot re-learn the position upwards, except for when you key off and key on the ignition, it will move up the minimum tps by .02 volts. If this voltage varys more that a few hundredth's of a volt , your idle will hang. Here are some of the causes I have seen for this problem:
1) Big throttle bodies. The big throttle bodies seem to have weaker springs than the original throttle bodies . In addition, I have seen the throttle shaft cause the tps to bind up on some of the accufab throttle bodies . To resolve that problem, I carefully filed the blade that goes into the tps . Syncing the throttle bodies can help, but really should not be necessary if you can get the throttle body to close by itself .
2) Bad tps . The tps is probably the most commonly replaced sensor here at our
shop. They are very susceptible to moisture. Recently Chrysler came out with
a revised part that has a small silicon seal that helps prevent moisture from getting in.
3) Poor electrical connections, there have been several cars that were fixed by doing a voltage drop test , and isolating connectors that had high
resistance.
4) Faulty pcm . Although not common, I have seen pcm’s that had internal
grounding issues .
The second cause has to do with the pcm calibration. Typically I see this problem more on cars that have modified engines although I have seen it on relatively stock cars . The lower the engine vacuum, the more that this seems to be a problem. This also usually causes a more severe idle hang (1700 and up.) Before I get into this, we need to think about a couple of things about how and why a viper controls idle. First, sometimes it is normal for the idle to stick at around 1200 rpm’s until you come to a stop. This is a dash-*** function that is there to help prevent stalling and improve emissions. Second is that these controllers have a adaptive memory for the idle control system, much like the adaptive system for the air fuel. The memory is non-volatile, and stays in the ecu until it is reset with the drb or the battery is disconnected. Third, is that there are two distinct modes of operation with the pcm . Idle and off idle. When the pcm thinks it is time to idle, it will try it’s hardest to do that, when off idle, it has a different strategy for fuel, timing, and ais control. Forth, above a certain rpm, I have found that the ecu will not go into idle mode and take control of the idle rpm’s. This is a important one to remember , because if you have a calibration problem that is causing your idle hang , you can usually force the car into idle mode by lugging it with the clutch to force the rpm’s below around seventeen hundred . To fix this problem, it is necessary to re-map the some of the ecu tables.
It looks like a lot of you guys have struggled with this problem , best thing to do , is to get your hands on a scan tool with enhanced Chrysler support , and make sure that it is not a tps problem . If anyone wants to talk to me about this, feel free to give me a call.
- Chris 3108416996
I’m going to chime in here, because I think I might be able to help out with this. From my experience fixing many Vipers idle hang, there seems to be two main causes.
The first, and most common cause, is a slight shift in the closed throttle minimum tps voltage. The pcm learns this voltage after a battery reset. If, while the car is running, the voltage goes lower that what it learned at key on, it has the ability to “re-learn” the minimum position. It cannot re-learn the position upwards, except for when you key off and key on the ignition, it will move up the minimum tps by .02 volts. If this voltage varys more that a few hundredth's of a volt , your idle will hang. Here are some of the causes I have seen for this problem:
1) Big throttle bodies. The big throttle bodies seem to have weaker springs than the original throttle bodies . In addition, I have seen the throttle shaft cause the tps to bind up on some of the accufab throttle bodies . To resolve that problem, I carefully filed the blade that goes into the tps . Syncing the throttle bodies can help, but really should not be necessary if you can get the throttle body to close by itself .
2) Bad tps . The tps is probably the most commonly replaced sensor here at our
shop. They are very susceptible to moisture. Recently Chrysler came out with
a revised part that has a small silicon seal that helps prevent moisture from getting in.
3) Poor electrical connections, there have been several cars that were fixed by doing a voltage drop test , and isolating connectors that had high
resistance.
4) Faulty pcm . Although not common, I have seen pcm’s that had internal
grounding issues .
The second cause has to do with the pcm calibration. Typically I see this problem more on cars that have modified engines although I have seen it on relatively stock cars . The lower the engine vacuum, the more that this seems to be a problem. This also usually causes a more severe idle hang (1700 and up.) Before I get into this, we need to think about a couple of things about how and why a viper controls idle. First, sometimes it is normal for the idle to stick at around 1200 rpm’s until you come to a stop. This is a dash-*** function that is there to help prevent stalling and improve emissions. Second is that these controllers have a adaptive memory for the idle control system, much like the adaptive system for the air fuel. The memory is non-volatile, and stays in the ecu until it is reset with the drb or the battery is disconnected. Third, is that there are two distinct modes of operation with the pcm . Idle and off idle. When the pcm thinks it is time to idle, it will try it’s hardest to do that, when off idle, it has a different strategy for fuel, timing, and ais control. Forth, above a certain rpm, I have found that the ecu will not go into idle mode and take control of the idle rpm’s. This is a important one to remember , because if you have a calibration problem that is causing your idle hang , you can usually force the car into idle mode by lugging it with the clutch to force the rpm’s below around seventeen hundred . To fix this problem, it is necessary to re-map the some of the ecu tables.
It looks like a lot of you guys have struggled with this problem , best thing to do , is to get your hands on a scan tool with enhanced Chrysler support , and make sure that it is not a tps problem . If anyone wants to talk to me about this, feel free to give me a call.
- Chris 3108416996
IEATVETS
Enthusiast
Re: Random High Idle / Sticking Idle - <master thread>
OK, here is the latest on my end. Replacing the TPS does not do a thing. I took mine in the other week and replaced it under warranty and nothing. Disconnected the computer to reset it and that did nothing. Now, mine is even surging as well. RPM's go up and down beteen 600 and 1100 rpm's. But what is weird is this.........when I am just sitting waiting for the light to turn and the idle is going up and down, if I let the clutch pedal out about 2-3 inches it goes away!!?? I was told that the surging is more than likely a vaccuum leak. Finding it is the hard part. Having some work done soon to try to resolve this and will post with results.
OK, here is the latest on my end. Replacing the TPS does not do a thing. I took mine in the other week and replaced it under warranty and nothing. Disconnected the computer to reset it and that did nothing. Now, mine is even surging as well. RPM's go up and down beteen 600 and 1100 rpm's. But what is weird is this.........when I am just sitting waiting for the light to turn and the idle is going up and down, if I let the clutch pedal out about 2-3 inches it goes away!!?? I was told that the surging is more than likely a vaccuum leak. Finding it is the hard part. Having some work done soon to try to resolve this and will post with results.
vprtech
Enthusiast
Re: Random High Idle / Sticking Idle - <master thread>
Ok , your situation is different . I have found that the 92-95 SBEC vipers are very tempremental with the idle stablility when you do engine modifications . Please call me , as I believe I can help you with this problem.
Ok , your situation is different . I have found that the 92-95 SBEC vipers are very tempremental with the idle stablility when you do engine modifications . Please call me , as I believe I can help you with this problem.
SYNFULL
Enthusiast
Re: Random High Idle / Sticking Idle - <master thread>
I drove my car for 45 min. yesterday and thought it was gone. Then it reared it's ugly head. It's very strange because at one light it will idle fine and the next light it will idle at 1200-1500. Blipping the throttle does nothing. Thne at the next stop it will idle fine. What makes matters worse is after it starts happening the car seems to get really hot- I don't know if that's the cause or symptom of the high idle.
I am going to check for vacuum leaks by spraying wd-40? around the vacuum lines when the car is running.
My gut feeling is that it is wiring somewhere that is being affected by my recent installation of headers. I think the wiring is getting very hot and screwing something up with the idle. But then again I am no viper tech
I drove my car for 45 min. yesterday and thought it was gone. Then it reared it's ugly head. It's very strange because at one light it will idle fine and the next light it will idle at 1200-1500. Blipping the throttle does nothing. Thne at the next stop it will idle fine. What makes matters worse is after it starts happening the car seems to get really hot- I don't know if that's the cause or symptom of the high idle.
I am going to check for vacuum leaks by spraying wd-40? around the vacuum lines when the car is running.
My gut feeling is that it is wiring somewhere that is being affected by my recent installation of headers. I think the wiring is getting very hot and screwing something up with the idle. But then again I am no viper tech
SYNFULL
Enthusiast
Re: Random High Idle / Sticking Idle - &lt;master thread&gt;
Jerry,
You never let us know if the check valve solved the problem. What's up -
Gary
Jerry,
You never let us know if the check valve solved the problem. What's up -
Gary
