If Idle Hang were a person.......

[ChicagoGTS]

I'D BEAT HIS A$$ NHL STYLE! I cannot for the life of me figure this out. 1700 RPM in nuetral while cruising and as soon as I come to a stop like clockwork it "usually" drops back to normal. On a hard run it will pause at a 1000 at a stop then seconds later back to normal. I've been trying to sync the 70mm accuCRAPS. I can back off the TB's enough so that when the A/C is on the car run's perfect when warm. But then the car seems to have a rough cold-idle (hunting and/or dropping to around 100 RMP and then climbing back to normal when it starts to warm up). But as soon as I try to get more aggresive with the TB adjustments I get the idle hang back. I can't find a happy medium. Oh, and I recently had the Battery, TPS, and ISC replaced as well as tightened the driver side TB spring. I've read a few threads that claimed this behavior is normal, but as far as I know "ALWAYS-ON CRUISE CONTROL" was not an option on my year! I've read a few hundred other threads on idle hang and intake leaks that sounded similar to my problem; but where exactly are the vaccum spots to test with the propane bottle? And has this ever worked for anyone?

~Matt~

 

[PhoenixGTS]

Thank you for letting me know my car does not have a "special" problem (I thought it was the T-bodies and cam in my car). Same exact symptoms for me. Does not sound like something a VEC2 could fix either.

 

[Kiaser]

Who all has actually seen recorded improvements with 70mm throttle bodies anyway? Has anyone ever put these on and tested before and after in similar testing conditions (dyno)?

 

[Sean Roe]

The only way I know of to turn "off" the factory idle hang (the one that is programmed to hold the RPM up while the car is moving, but out of gear) is to put a restrictor in the IAC hose.

Regards,
Sean

 

[Gerald]

Here's what I did and it FINALLY worked. I've had idle hang for nearly 5 years. Doug Levin gave me a call and told me what he does is put a new, much stronger spring on the return spring of the linkage. I couldn't figure out how to do this so I just jammed (yeah, I said jam) something metal between where the spring attaches and what it attaches to to make the spring MUCH tighter so it has MUCH more return force. Voila.... VERY LITTLE to almost no idle hang....
Just take a look at the linkage and you'll see what I mean about the return springs.

Try it, it literally takes 5 minutes to tighten both springs for left and right side throttle body linkage return springs.


Gerald

 

[C O D Y]

Isn't idle hang programmed in to the factory computer? I thought it does that to burn off excess fuel as part of the emmision control. It seem to be happening to cars that have been modified, so maybe more tuning is the answer.

 

[thebigsnake]

Thanks for the restrictor tip Sean. I stuck something in there which had a bigger diameter opening then the one you mentioned. Haven't had the chance to try the car yet though. It took a lot of time wading through everybody's pontifications on a fix(...blip the throttle; ...try to stall it in gear;...more play in throttle cable;...tightening butterfly springs; etc.etc.)'till I read your post finally.
I'd like to keep the beast as calm as possible when I'm motoring with it.

 

[PhoenixGTS]

Who all has actually seen recorded improvements with 70mm throttle bodies anyway? Has anyone ever put these on and tested before and after in similar testing conditions (dyno)?

My car had them when I got it (not even sure of ID), but the Belangers and Albert Box (local to me) claim they make very little power on the very top end - to the detriment of torque down low - so the "under the curve" power is reduced in total. I might even go back to stockers.

 

[thebigsnake]

Idle hang gone. Sean's the man.

 

[ChicagoGTS]

Please elaborate, do you have the 70mm TB's?

 

[Todd Richmond]

Check out my post a while back - it lists everything I found on threads (and tested myself) and the combination that worked for me (strong return spring + IAC blockage). I have not had a single issue since

 

[ChicagoGTS]

What about cold starts?

 

[BadVenm]

I have for the second time found myself with a Viper with idle hang.

I have owned three Vipers, two currently.

NONE of these Vipers had idle hang. That was until I modified them.

My 94 never had idle hang when stock, but once modified, idle hang out the ****!

My 97 is stock and will remain stock, no idle hang.

My 99 when stock never a hint of idle hang. I just picked it up Friday afternoon with modifications. Guess what, idle hang.

Everyone on here acts like you just have to accept it. I did a search and read a few of these threads on idle hang. So today, I tried the 3/4 inch IAS plug with the 21/64 hole it in, as recommended in this thread.

Here's my experience with this plug idea.

After hard runs, the idle dropped just like it should. At least in the first test run. (test run was about 15 miles long with some REALLY hard runs, see another post about WAXING a crotch rocket)

But under normal driving conditions it hung at about 1,500 RPMs for a few seconds and then dropped to 1,000 RPMs for a few seconds, then dropped to normal. Complete process takes about 10 seconds, maybe 15 at the most. Still embarrassing at a stop light when everyone is checking out the car.

I'm wondering since this did seem to help some, at least on the first test drive, would a different size hole do better? Has anyone tried a different sized hole? Bigger, smaller, any results?

I will give it a try when time permits. It's always hard to play with the cars during the week. Maybe next weekend.

If a different sized hole helps I will post results.

 

[PhoenixGTS]

Alright let me tell you where I am with my idle hang. First, I had a smooth tube off to change the serpentine belt and my throttle-bodies are a full three inches inner diameter so I guess you would call them 75mm units. I tried the restrictor in the idle air hose and noticed little if any difference. Visited my local tech to get my 998 Recall redone and when I mentioned idle hang he said let's try something. He unplugged all the computer harness connectors (right in front of the driver's feet in the engine compartment) and put dielectric grease in the multi-pin connectors. His thought is that idle hang is adversely effected by hot under-hood temps and the grease helped wick heat away from the terminals. Sounded farfetched to me but darn if it did not help a lot. But, it is not gone. I am now in BadVenm's position where it does not hang after hard running, but will hang after cruising. However, mine hangs until I actually stop. I know this is not any help. Just another data point. BTW, Ace Hardware by me has some specialty parts they call spacers that might work nice for making idle air hose restrictors.

 

[ChicagoGTS]

I found that the smaller I went the better it got, but at a cost. When I restricted the IAC that much, I found that when cold my idle would hunt from 500-1000-500 and sometimes it would fall on it's face to around 200RPM. Talk about embarassing, nothing like your viper almost dying out infront of friends. I really think this an oversized TB situation that can only be resolved by putting the stock ones back on. I'd be curious to see if anyone with stock TB has this. Pheonix my Idle hang is a just like yours.

~Matt~

 

[PhoenixGTS]

ChicagoGTS I have an update. Could be good news for you. I removed my intake manifold in order to get it painted. When I reinstalled it I synched the throttle bodies. I found that the passenger side was opening before and farther than the driver's side which is backwards from how it is supposed to be. I set them up equal (honestly I tried to get it so I could feel the driver's side "move" first but my fingers are not that sensitive) and they are much better than before. But the the news is the big side benefit - in addition to smoother parking garage speeds, NO MORE IDLE HANG! So check out you t-body synchronization.

 

[AJT]

How do you Sync. throttle bodies??

 

[ChicagoGTS]

You are right!!! Holy ****, what a difference! I took off my airbox at lunch and discovered the same thing. I turned back the passenger side screw and ****, no low speed bucking and the idle hange is about 95% better. It does still hang under heavy load though. I'm going to use a sharpie and mark the screws for good reference since it's running better than it ever has and continue to make adjustments. One thing I did notice is that when you get to the range of where (I think) it's supposed to be the adjustments become much finer in terms of affecting the idle. Meaning one 1/100th of a turn will change the idle note either way, mine was way out of sync so there was about three full revolutions on the passenger side screw.

Thanks for sharing Phoenix,

~Matt~

 

[PhoenixGTS]

How do you Sync. throttle bodies??

There was a detailed post about it in the last couple of weeks, but here is what I did. When you floored the trottle, mine were so bad that you could clearly see the the passenger side was open more than the driver's. If you look, in the passenger side of the common shaft that connects the two t-bodies is a small screw with a lock nut (very small nut - maybe 7mm). Loosen the lock nut and screw the screw as appropriate to get the butterflies opening evenly. Once you are close, you touch both butterflies at the same time with a finger and have someone barely open the throttle. You are supposed to feel the driver's side open before the passenger side (this supposedly compensates for the IAC being on the passenger side). Just tighten the lock nut on the adjusting screw and you are done.

 

[AJT]

Thanks I am going to try that tonight.

 

[BadVenm]

Chicago,

Any other ideas? It didn't work on mine. But then again, I've never had idle hang on any of my 3 stock Vipers, only once modified.

I checked my t-bodies tonight and the driver side opens ever so slightly before the pass side does. At wide open throttle it also looks like the driver side is open just a hair past WOT while the pass side is exactly at WOT.

I still have idle hang after an easy cruise. And at that, it's still small. Maybe 2 to 3 seconds as it slowly idles down, then it drops to idle. And it will do that while making any easy cruise driving 60 or above and I push in the clutch while coasting at 60 it will hang for 2 to 3 seconds then drop to idle.

But I have no idle hang after a hard run?????

I have the plug in with the small hole that Sean Roe recommended.

How much diff in opening is there in yours? Mine is almost hard to detect, but with a finger on each one and the wife pushing the gas pedal you can just barely feel the driver side open first. But just barely. But at WOT you can visibly see the driver side is past WOT while the pass side is not.

SOMEONE out there has to have an answer! HELP!!

 

[STUGOTS]

where is idle hang at what RPM?

mine will hang just until I make a complete stop but it hangs at 2k RPM is that normal?

 

[PhoenixGTS]

where is idle hang at what RPM?

mine will hang just until I make a complete stop but it hangs at 2k RPM is that normal?

What you are describing = "idle hang."

Update: bad news. My idle hang is back. And the low speed bucking seems worse. I am going to back the passenger-side butterfly off compared to the driver's and see what happens.

 

[STUGOTS]

no low speed bucking here but when driving only when comming to a stop it goes to 2k.

 

[Shelby3]

I too recently joined the "idle hang" club. ***** to be a member.

 

[PRVT JET]

It's funny, when my vec1 is set at 0-0, It's there. When I change the setting, I hardly get the idle hang.

 

[BadVenm]

Okay, latest update.

I checked t-bodies, everything there checks out as they should. Yesterday while driving around I noticed the hang was still a 2 to 3 second issue then it dropped.

Sometimes it would drop and actually die! This while the car is up to temp. This also while I have the plug with the hole in the IAC hose.

So tonight I took the plug out and expected idle hang to be back up in the 2,000 RPM range for 10 second, or until I slowed to a stop.

Without the plug the car acted exactly the same! The idle hang only lasted 2 to 3 seconds then dropped. Sometimes it dropped so low the car died!

Now what the hell is going on??????

ANYONE???????

 

[PhoenixGTS]

We're going to beat this thread until idle hang is into submission. My latest is that: 1) I found out I had forgotten to plug in my IAC plug last time I was working on the car so perhaps that is why my hang came back, and 2) I fine tuned my throttle body synchronization tonight. Found that driver's side was still not opening before passenger side so I backed off a whole 3 turns on the adjustment screw - found that was too much as the driver's side blatently opened before the passenger side - and took it back in a turn. I will report if I got rid of the bucking after I drive through the parking garage at work tomorrow (yes a Viper is my daily driver).

I unplugged the computer harness cables to do some detailing work so it may be sometime before I can tell for sure the hang is gone.

And thanks to my Dad for lending me his 1997 C2S while I work on the Viper. Nice car but SLOW! (But I do wish the Viper was that quiet)

 

[PhoenixGTS]

Update: no idle hang whatsoever, and low speed bucking is virtually gone (I can "make" it do it if I try). Might tweak the throttle-body synchronization so the driver's side opens a little more, but unless the PCM "learns" something I am basically there. Thanks for all the help guys.

 

[Jerry Dobson]

Phoenix, update us after a few hundred miles. Problem sitll fixed?

So many of us have this problem.

Question:
Are you guys running KN Filters? Are they factory oiled or have you re-oiled them? I am curious if filter oil could be effecting the sensor. The factory air filters are dry. I know this is a stab in the dark but something is causing the problem and most of us run KNs.