Another Idle Hang Resolved Thread

[Solid Red 98]

So A few months ago I replaced my temperature sensor. It was giving me inaccurate readings on the gauge and elevated levels of stress while in traffic. Finally the sensor just got it over with, by reading an overheat, on a cool easy run with no boiling. I returned to base in full pucker mode, and promptly picked up a new sensor and quickly installed it. I have had no Idle hang since, and the overall performance of the engine seems to be improved. Here is my theory: The faulty sensor was sending a message to the ECU that made it mess around with the idle, trying to reconcile a false set of engine operating conditions. Perhaps anyone still suffering with the problem might try this as a fix--it is pretty cheap, quick, and easy job. At the very least, it may tame some of those wide and uncomfortable temperature swings that I had been experiencing. Am I off base here?

 

[B235R]

+1 on that,performance is really better,changed mine today and temp.reading is also solid right now

 

[Ratical2]

So A few months ago I replaced my temperature sensor. It was giving me inaccurate readings on the gauge and elevated levels of stress while in traffic. Finally the sensor just got it over with, by reading an overheat, on a cool easy run with no boiling. I returned to base in full pucker mode....

You have a way with words and I understand exactly what you are saying, having experienced something similar...

Glad you got it fixed!

 

[jmasin]

Excellent... Good to hear you resolved the issue.

When you say wide swings... how wide?

I'm still learning this car and definitely see swings up, the fan comes on, swings down, swings up etc... just curious how that equates to what you were seeing.

 

[dave6666]

Excellent... Good to hear you resolved the issue.

When you say wide swings... how wide?

I'm still learning this car and definitely see swings up, the fan comes on, swings down, swings up etc... just curious how that equates to what you were seeing.

Go look at my dual pusher fan thread at VA or TVG. I've got diagrams of the gauge swing.

__________________________________________________

Please note the complaint-free content. Dave, contemporary mod-rice Viper/Ricer owner, and I approve this message.

 

[Red Shift]

Hmmm, doesn't make a lot of sense to me. Then again, I don't know how the control on the IAC motor and PCM function together. Just wanted to check out this thread because I am having worse idle hang after swapping in a different engine. I'll clear out the PCM tonight and work from there.

 

[dave6666]

I solved the idle hang on my '01 by cleaning the IAC. Just got to give it a week to relearn when done.

__________________________________________________

Please note the complaint-free content. Dave, contemporary mod-rice Viper/Ricer owner, and I approve this message.

 

[Jack B]

Hmmm, doesn't make a lot of sense to me. Then again, I don't know how the control on the IAC motor and PCM function together. Just wanted to check out this thread because I am having worse idle hang after swapping in a different engine. I'll clear out the PCM tonight and work from there.

You can watch the step position over the OBD port. If you can log thru the OBD, you can also plot the the step position versus, rpm, LTFT or STFT. That should show quite a bit.

My guess is that you will find some activity during the idle hang. When I had the idle hang issue it was caused by a bad O2 sensor ground. The main ground for the O2 sensors is a wire that originates in a cable assembly near the ac compressor. That cable runs from left to right and the O2 ground wire bolts to either the compressor or the block, but, attaches right near the front of the compressor.

It was too hard to get back at the original connection so I grounded both O2 sensors to a common point on the block - that solved the issue.

 

[ViperTony]

You can watch the step position over the OBD port. If you can log thru the OBD, you can also plot the the step position versus, rpm, LTFT or STFT. That should show quite a bit.

My guess is that you will find some activity during the idle hang. When I had the idle hang issue it was caused by a bad O2 sensor ground. The main ground for the O2 sensors is a wire that originates in a cable assembly near the ac compressor. That cable runs from left to right and the O2 ground wire bolts to either the compressor or the block, but, attaches right near the front of the compressor.

It was too hard to get back at the original connection so I grounded both O2 sensors to a common point on the block - that solved the issue.

I believe it's a black wire that grounds on a bolt that holds the AC compressor. I ended up unbolting it and re-routing the black wire over (as opposed to underneath) the compressor to gain an addition 2" of slack for the O2 sensor on the driver's side. In fact, I believe the wire harness containing the O2 wires runs between the compressor and mounting points.

 

[Solid Red 98]

Excellent... Good to hear you resolved the issue.

When you say wide swings... how wide?

I'm still learning this car and definitely see swings up, the fan comes on, swings down, swings up etc... just curious how that equates to what you were seeing.

The temperature would hit normal at about 190 or so within a half mile of driving, but as soon as you got into traffic it would start to climb. First 195-200, then 225--at times almost 250, but never boiling, burping, or anything even close. After a while it seemed like a reasonable pattern in terms of conditions, and a big powerful engine but, still too exaggerated. Another telltale sign was no correlation between the fan and the "high temps".

I checked the cooling system for air, as well as the overflow bottle, and fan solenoids, but no joy. Finally the sensor did me a favor an crapped out. Since its replacement the engine operation has been much more consistent along with more sensible gauge operation. No idle hang since. I did a number of searches and messed with the IAC and its wiring, but still the occasional hang. Submitted for your approval....

 

[Solid Red 98]

You can watch the step position over the OBD port. If you can log thru the OBD, you can also plot the the step position versus, rpm, LTFT or STFT. That should show quite a bit.

My guess is that you will find some activity during the idle hang. When I had the idle hang issue it was caused by a bad O2 sensor ground. The main ground for the O2 sensors is a wire that originates in a cable assembly near the ac compressor. That cable runs from left to right and the O2 ground wire bolts to either the compressor or the block, but, attaches right near the front of the compressor.

It was too hard to get back at the original connection so I grounded both O2 sensors to a common point on the block - that solved the issue.

So from what you say then, a different set of sensors were causing your idle problems. I suppose that idle hang is likely caused by one faulty sensor or another. Since the Viper is a fairly simple machine by modernish standards, checking the most relevant sensors, in turn, might find the boogieman. I for one, am happy to be finally rid of that embarrassing, and annoying idle hang.

 

[cfiiman]

Just curious what was the replacement procedure?

 

[Solid Red 98]

Very simple replacement. Nestled on the driver's side front of the engine ahead of the valve cover, down and in a bit, you can follow the wire harness to the sensor. Remove the plug,(without breaking the clip latch) leaving the sensor exposed. Using a deep socket (can't remember the size) back it out. Mine was easy to remove. You will lose a negligible amount of coolant, so have some towels ready. The new sensor will have thread dressing already applied. Thread it in making sure it is not cross threaded, tighten so that you don't have to twist the wires beyond their natural set when reconnecting. Also, there is no need to over tighten, as it is not going anywhere. It is a brass taper thread for a good seal. Connect plug and you are done. I didn't disconnect the battery for this, but it is a good idea if you want to be really safe when dealing with electricals. Start the car and check for leaks. Ten minutes total for my GTS, then out for a drive.

(sorry for the lack of pictures, but this is no more difficult than removing a spark plug)

 

[eucharistos]

good write up sr98,

thanks