Here's how we eliminate idle hang when needed....

[Sean Roe]

Here\'s how we eliminate idle hang when needed....

Hi Everyone,

As idle hang is always a topic among stock and modified Vipers, here's how we eliminated it on a car that had no reason for it other than PCM programming ('97 GTS). Get a piece of 3/4" round stock from the hardware store (metal, wood, plastic, etc..) and cut off a piece about 1/2" to 3/4" long. Drill a 21/64" hole in it. Put this "restrictor" in the idle air control hose that goes from your airbox to your idle air control motor, on the passesnger side of the engine. Experiment with a larger hole if the idle is too low with the A/C and lights on, but this worked perfect for us at sea level. It completely eliminating the idle hang that bugged the heck out of the car owner.
Hope that helps some people out.

Regards,
Sean

 

[Gerald]

Re: Here\'s how we eliminate idle hang when needed....

Can u take a photo? What about those of us who's IAC Motor just has a small air filter on it and it doesn't go to the air box?

 

[ViperGTS]

Re: Here\'s how we eliminate idle hang when needed....

21/64" is 8.36 mm

--------------------------------hose
|---------|restrictor
hole->
|---------|
--------------------------------
THIS WAY?

 

[Russ Oasis]

Re: Here\'s how we eliminate idle hang when needed....

Here's a better way...get rid of a competition computer and / or enlarged throttle bodies. They screw up the idle and add very little power.

 

[varanus]

Re: Here\'s how we eliminate idle hang when needed....

Sean, I tried this tonight and the car could barely idle. Should I continue to drill bigger holes and if so by how much each time?
I hope this helps as my idle hang is pretty nasty (almost like the cruise control Dodge didn't put in)

 

[Sean Roe]

Re: Here\'s how we eliminate idle hang when needed....

Hi Kevin,
Yes. Increase the hole size by 32nds or 64ths of an inch until it idles properly.
The first one we did showed 5/16 to be too small (idled poorly), but 21/64 to be just right (check with lights and A/C on).
Regards,
Sean

 

[Vip-RT10]

Re: Here\'s how we eliminate idle hang when needed....

Funny this is what happens to me and that is what I did about a month ago. My problem is similar. I have a 93 RT/10 and just recently changed over the engine with Scott at Elite Motorsports to a 97 engine model.

We used the same PC and just adapted some wires to work with the new engine, relocated some sensors, and make different vacuum lines. It runs fine, but it has a huge problem with the idle. It would idle at 2500 RPm's. I installed a rubber plug into the IAC valve and drilled 4 holes in a progressive manner until the RPM dropped to 700 RPM at idle. I decided to drill 4 holes all in different sizes, the largest being about 2mm (sorry, I use metric). This would make different holes and maybe eliminate any "whistleing" it may cause. I them bought a cheap APC little filter and found a suitable elbow to use from the fine selection on "HELP!" products at Auto Zone. I drilled out one end of the elbow a bit to better plug into the IAC valve and the other end is groved so that the filter does not fall off. The plug is inserted into the IAC valve and the new filter fitting is plugged on to the IAC valve, leaving that protected from dirt. I could get some pics if there is a need for it.

I know this is not normal and it didn't do it before, but this is how it is cured now. There are no IM leaks and all is good, so there is no explanation on why the car does it.

 

[Mike 99ACR]

Re: Here\'s how we eliminate idle hang when needed....

Sean what causes this ? My car did this for the first time ever this past weekend. Does it have something to do with the extreme heat and humidity?

 

[Vip-RT10]

Re: Here\'s how we eliminate idle hang when needed....

It's probably the dreaded "Y2k03" bug...

 

[ndvipergtsr]

Re: Here\'s how we eliminate idle hang when needed....

I just did mine simialar but it was too late to run to the store i used a 3/4 headed open lugnut 1/2 thread and took it to the grinder and rounded it so it just slipped in the hose and idle hang is gone. I know it is cheezy but it worked and it was free. Jerry

 

[Sean Roe]

Re: Here\'s how we eliminate idle hang when needed....

Sean what causes this ? My car did this for the first time ever this past weekend. Does it have something to do with the extreme heat and humidity?

I'm really not sure what the parameters are that cause it, but the idle air control motor is doing what the PCM is telling it to do (open the valve and keep the idle up). Might just be programmed to keep the cats hot.

 

[ViperGTS]

Re: Here\'s how we eliminate idle hang when needed....

I have no statistic about the idle hang, however, if it is hot outside - like last weeks - the idle hang occurs more often...almost no humidity (30%-35%) here, very dry weather.

 

[JimDavis MT 97GTS 650R]

Re: Here\'s how we eliminate idle hang when needed....

Been there. Done most of the above. After 50 to 100 miles the PCM adjusted to the modification and the problem returned. Me thinks these cars have a little of the old Jaguar blood in them. I did find that the throttle plate adjustments were very critical. None the less, if you run hard, you will experience some hang.

 

[ViperGTS]

Re: Here\'s how we eliminate idle hang when needed....

:-(((
The IDLE HANG seems to be a very common problem - SOFTWARE?
Why isn´t Dodge or PVO able to find and solve the problem?
:-(((

 

[Tom and Vipers]

Re: Here\'s how we eliminate idle hang when needed....

I have one clue to add, my 96 GTS (Skiles Bad Viper) hangs very noticeably around 9000' altitude. Back at 5-6000' it doesn't do it.

Go figure.

 

[JimDavis MT 97GTS 650R]

Re: Here\'s how we eliminate idle hang when needed....

:-(((
The IDLE HANG seems to be a very common problem - SOFTWARE?
Why isn´t Dodge or PVO able to find and solve the problem?
:-(((

It is my belief that Chrysler/Dodge doesn't give a rip about our "hanging idle" problem or they would have suggested a fix by now. Instead, they just moved on to the new generation motor, expecting us to trade up sooner or later. A typical corporate solution. HAY PVO, I HOPE YOUR LISTENING!!!...not

 

[Russ Oasis]

Re: Here\'s how we eliminate idle hang when needed....

Guys,
I had the hang problem bad. I got rid of the Mopar Competition Computer and then got rid of the oversized throttle bodies and the problem went away. If you want to drive your car on the street, the hang problem is quite annoying. At the drag strip it doesn't matter.

 

[Vip-RT10]

Re: Here\'s how we eliminate idle hang when needed....

To me, this is not normal that we have to plug up an opening that is supposed to be open, so what gives? It has to be the PCM. I don't have any manifold leaks, so what is the problem? It really bugs me.

 

[ViperGTS]

Re: Here\'s how we eliminate idle hang when needed....

my car is stock, except for the HF-cats and the corsa.
The idle hang was there before i switched exhaust and to the US PCM and is still there with the US computer. When I switch A/C off (during idle hang!) the idle goes back to normal.

 

[JimDavis MT 97GTS 650R]

Re: Here\'s how we eliminate idle hang when needed....

Dare I suggest the Viper community bring a class action targeting this problem? Complaints could be directed to the N.T.S.B. as a safety related issue. Modified cars might not qualify. After all, they recall cars for sticking cruise controls etc. Wouldn't you think a 450+ HP vehicle with a hanging throttle would be a legit issue? Your Comments please.

 

[axe]

Re: Here\'s how we eliminate idle hang when needed....

The idle hang in my viper appeared to be caused by a bad PCM.

When people refer to idle hang, what exactly are the symptoms?

On my 96 GTS, the "normal" idle hang that I experienced before was when rolling to a stop, it hangs around 1300 RPM. Once car stops completely, RPM
immediately drops to normal.

The "abnormal" idle hang that started happening about 1200 miles ago was when rolling to a stop, it would hang above 2000 RPM. Once the car stops completely, RPMs stay up for a few seconds, then drop to normal. If I unplugged the PCM, the idle hang would go away, but come back after driving around 50 miles.

We plugged in an OBD2 readerand saw that the MAP sensor always read low, at idle and at full throttle. Tried the MAP sensor in a 98 GTS, and the MAP sensor would read a range of values both low and high. We then put a 98 PCM in the 96 GTS, and then the MAP sensor started reading a range of values. After driving over 100 miles, the "abnormal" idle hang has not returned, and the "normal" idle hang has.

 

[varanus]

Re: Here\'s how we eliminate idle hang when needed....

My idle hang was so bad that one day I was cruising down a winding hwy at about 60mph. I would let off the gas and the car would start to slow down then accelerate back up to 65 mph on it's own. Just driving around town normally with gentile accelleration coming to a stop and putting the car in neutral it would idle at about 2000 rpm for at least 20 seconds sometimes never coming down at all unless you turned motor off.
As I said a while back, driving thru canyon roads and letting off the gas expecting to slow down is a surprise when you don't scrub off speed and wind up driving thru turns faster than you expected because of the idle hang

 

[JimDavis MT 97GTS 650R]

Re: Here\'s how we eliminate idle hang when needed....

No doubt mods like a more agressive cam & larger TBs may aggravate the problem. Just curious how many of you stockers have experienced this problem. I suspect quit a few.

 

[Vip-RT10]

Re: Here\'s how we eliminate idle hang when needed....

I have it when I turn on the engine right away..........I have stock '93 PCM, 97 engine, Sean Roe exhaust and that is it.

I would jump on a complaint for the NTSB....

 

[jcaspar1]

Re: Here\'s how we eliminate idle hang when needed....

The only hang idle I have noticed is a slight pause in the revs as they drop from 2500 out of gear. Will pause slightly at about 1500 rpm before dropping to idle. Sean's mod above eliminated this. I did have one episode associated with a high idle speed (about 2500) that would not come down. Replaced battery and it solved that problem

 

[Jerry Dobson]

Re: Here\'s how we eliminate idle hang when needed....

Jeff, Maybe replacing the battery only reset the PCM. Has the problem come back?

I think most of these cars with the problem are stock...with the exception of K&N's. I know there were some complaints the heavy oiled filters... can create a sensor problem. But I doubt that we all have this problem.

I had a high idle a while back. Then it went away for a few months. Now it started raining here and the problem is back. I don't drive in the rain, but maybe the humidity?

Last night I was cruising the park strip in St Joe Mo. About 10 miles of tight turns. A few times I let off the gas and I was expecting engine braking... WRONG.

This is such a problem, Dodge should do something.

Jerry Dobson

 

[99 R/T 10]

Re: Here\'s how we eliminate idle hang when needed....

Can we get picture of the fix? Somebody's got to have a picture?????????

 

[Larry Macedo]

Re: Here\'s how we eliminate idle hang when needed....

I had a conversation with a DCX engineer back in 98 regarding this issue since unmodified Viper's were exhibiting the same idle hang as modified Viper's. Most seemed to hang when the ambient temperature was above 90 degrees and close to 220 degrees indicated on the temp gauge. From what I gathered in the conversation, part of the cooling strategy within the PCM is to speed up the water pump which would in turn cool the engine at a faster rate.

 

[Jerry Dobson]

Re: Here\'s how we eliminate idle hang when needed....

Ryck,

are you out there? You did this....what was your outcome?

Jerry

 

[viper spray]

Re: Here\'s how we eliminate idle hang when needed....

I took apart my idle air control motor and cleaned it. It was gunked up. Idle hang went away for good.