Did anyone ever figure out the Idle Hang problem?

FLX109

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I have read past posts on this and it doesn't seem to have a definate cure, problems still exist, is it something we have to live with? Or is there a known cure? I'm sorry to bring it up again but it is a real pain in the ---.
I might be a new member of the club.

FLX109
 

Steve-Indy

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FLX109, have you searched the threads on this by Sean Roe ???

Try these for a starter:

Here's how we eliminate idle hang when needed....
      #303627 - 07/30/03 07:10 AM Edit   Reply   Quote Quick Reply  



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



Re: Here's how we eliminate idle hang when needed....
      #305044 - 08/03/03 10:48 AM Edit   Reply   Quote Quick Reply  



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



Re: Here's how we eliminate idle hang when needed....
      #306665 - 08/07/03 07:35 AM Edit   Reply   Quote Quick Reply  



Quote:
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.
 

Jerry Dobson

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FLX,

You are correct. To this date I have not seen a fix for the problem. There are only Band-Aids to mask the problem.

The above attempt helps some, but I have seen it create the reverse effect. When the Idle hang disappears, the car will not even idle with the update in place.

It is 100% a computer issue and not a mechanical problem. Some say:
"Adjust the throttle plates"
"It is a weak return spring"
“It is a weak battery, what they fail to realize is that they are only resetting the ECU with the battery replacement.

These are not the answers. If it was, the problem would not come and go.

When my car idles at 1200 RPM, I can turn it off and restart the car… perfect idle until I drive again.

I am using a DRB to monitor the sensors to isolate the problem. I will have to start a fresh post to help discover the problem.

I thought that it might even be bad oxygen sensors. I replaced mine with no help. I am looking at the IAC next.

Here is the issue with my car. If the temperature is below 60 degrees, it does it. I can drive most of the summer with no problems.

I am looking at what mods might have caused the problem. Most of the problem cars have K&N filters. Is the oil contaminating a sensor?

Most of the cars have headers. Is this somehow causing the problem?

Who has a BONE BONE BONE stock car with idle hang? (Smooth tubes and filters is not bone stock)
 

PhoenixGTS

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I fixed my idle hang

The big breakthrough for me was properly synchronizing the throttle bodies. Here is what I did:

1) put restrictor in IAC air hose (25/64 I think)
2) dielectric grease on PCM harness connections (local tech thinks idle hang is heat related and this helps)
3) synch'd t-bodies so driver's side opens slightly before passenger side.

After doing one and two and idle hang went away for awhile but cam back toward end of first tank of gas. After I synch'd the t-bodies is has been 5 tanks of gas or so and hang is gone. Caveat, now that it has finally cooled down in the desert (high 50sF or 60F in the morning) the car hangs for maybe first half mile of driving. I'm guessing until it sees a little heat, but after that, no hang at all.
 

STUGOTS

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Re: I fixed my idle hang

From talking to the top tuners I have found the following ways

1.performance pcm from Roe racing.
2.wooden dowl in the IAC.
3.and they way I have been dealing with it from Chuck Tator Pcm reset every 2000 or so miles.

Good luck guys
 

Shelby3

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Re: I fixed my idle hang

From talking to the top tuners I have found the following ways

1.performance pcm from Roe racing.
2.wooden dowl in the IAC.
3.and they way I have been dealing with it from Chuck Tator Pcm reset every 2000 or so miles.

Good luck guys

I've done all three and the only thing that works for a couple hundred miles is clearing the PCM memory. :confused: :usa:
 

Big Medicine

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Re: I fixed my idle hang

I read one time that the IAC motor is hyper sensitive to voltage & current. Someone told me to replace my battery & they were right.

But......

I have the opposite problem; my car refuses to idle, typically occurs after I wash my motor. For some reason, my battery goes south. When I replace the battery, I run strong for about 6 months (more than 2000 miles)& then the same problems:

Low Idle
Wimpy horn rapport for alarm set'
eventually won't crank

So every 6 months I head to Wally Mart & exchange my "faulty" battery for a brand new one; in reality, I'm prolly draining the thing with the alarm for months on end. A logical person would think that the alternator would cure the problem, but alas it doesn't work for me.

I read in the service manual that the IAC motor is controlled by the PCM based on 3 inputs:

cam position
throttle position
coolant temperature

If this is correct, a root cause analysis should center around the circuits & end devices that are input variables to the PCM, followed by an anlaysis of the circuit and end device (IAC motor) on the PCM output.

Continuity checks, analog device range precision, etc. If all those check out, it could only be programming. I find it difficult to believe that DC manufactured inconsistent PCMs, particularly since this isn't affecting EVERY Viper out there.

Bottom line, I bet, is that the PCM is not receiving accurate inputs, followed closely by the IAC motor is not receiving the correct pulse due to shorted circuit, OR the IAC motor is faulty.

One of these days when I get all the tools I need, I will chase my problem down; for now, I'll keep replacing the battery every 6 months.
 

ChicagoGTS

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Re: I fixed my idle hang

Big Medicine,

You may want to check your ground wires, especially the one in front on the driver side under the hood. I reseat mine as well as clean them with a wire brush every year, you'd be amazed at how fast they corrode. Also check the one on the front of the motor near the water pump. Also next time you go to walmart pick up a 2amp "trickle charger". They're $50 then you dont have to worry about leaving the alarm on for a month.

T/B synch helped but didn't cure for me, my bad idle hang happens when I run the car hard. However if I putt around I never get it, perhaps it's PCM and T/B related meaning if you're out of synch our you've put in acufab's the PCM react's abnormally. The one thing I know for sure is, that the car didn'r do it before I put the acufab's on.

Oh, and I forgot to add that I just replaced my IAC motor, it changed nothing. Gerald has also tried this with the same results. last I heard rear Sims made his idle hang go away, however that's definitely another bandaid and not a cure.

~Matt~
 

STUGOTS

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Re: I fixed my idle hang

From talking to the top tuners I have found the following ways

1.performance pcm from Roe racing.
2.wooden dowl in the IAC.
3.and they way I have been dealing with it from Chuck Tator Pcm reset every 2000 or so miles.

Good luck guys

I've done all three and the only thing that works for a couple hundred miles is clearing the PCM memory. :confused: :usa:

Then you have a "rare" one like me I have to do my every 200 miles or so as well Chuck said that most cars get more then 200 but I guess were the "rare" ones.
 

STUGOTS

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Re: I fixed my idle hang

Shelby3 I hope you have a good tech in TX thats cool with resetting it every 200 miles or so for free.

I got the wizard here hes great about it anytime its hanging "just stop by I'll reset it for you no problem" Chucks the man.
 
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FLX109

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Re: I fixed my idle hang

It seems to have started to happen when the temp got to be around 60 degrees or lower, It is really annoying, I was going to take the IAC out and check it, I thought maybe it might be dirty.

FLX109
 

Falconeer

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I bought my Viper a couple of months ago and it drove perfectly with no idle hang at all. Then after a couple of weeks the front of my waterpump cracked due to fatigue. I got this repaired at Dodge with an idle hang as a result. The engine idled between 1200-2000 RPM and the engine got very hot. They found out that it in fact was the entire waterpump that was bad and replaced it. They told me that the reason for the idle hang was because the engine was getting hot due to the waterpump not working properly, and therefore it kept the idle at a higher pace to get more coolant through the system. After they had replaced the pump and installed a new thermostat I just found out that it minimized the amount of times I was getting the idle hang. It still comes every time I drive but not as often and forceful as before though! Could the problem have something to do with the waterpump since it was when this unit failed the problem started to occur? It ***** with "cruise control" in the Viper, especially when you don't want it!! Dodge even cleaned the throttle body, replaced the AIS motor and calibrated the throttle positioning sensor but none of this works for me.. ?!?

If somebody out there finds out how to solve this problem, please tell me how!!!
 

AJT

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Doug reprogramed my computer & it seems that my idle hang is pretty much gone! I was also tired of having "cruise control"!

Andy
 

Fishtail

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I noticed the same thing on my car when it was stock. Now it's the opposite, after building the motor and mods the car doesn't do it anymore. Could it be the factory computers are not programed properly?

-Lou
 
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FLX109

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Cleaned the IAC, not that dirty, I guess I will try the dowl trick in the IAC hose now
 

Ulysses

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Before you do that, check all your vacuum hoses one more time for cracks or good seal. Then retighten your intake manifold bolts.
 
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FLX109

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I disconnected my plugs to my pcm, waited five minutes, reconnected and started car, took it for a ride, Idle hang is gone.

FLX109
 

Tom and Vipers

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The bad battery thoughts should also include a bad alternator that is outputting noise or an AC component. An AC component really messes with PCMs.
 
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