Stalling

Ahh, ... Finally a simple problem. The idle speed problem is due to you had the battery disconnected recently, and the diagnostic fault codes verify that. If you are reading the codes by watching the flashing of the Check Engine light, you are getting code 12 and code 55. There are no four-digit codes and on Chrysler products, no airflow codes.

Code 12 just means that power was recently lost to the Engine Computer. Translation: the battery or the computer was disconnected. Code 55 just means the Engine Computer is done flashing fault codes. You will get that one every time you read the fault codes.

When power is lost to the Engine Computer, it loses everything in memory related to sensor characteristics and operating conditions. All of that data is rebuilt as soon as you resume driving, without you even noticing, except for "minimum throttle". Until that is relearned, the engine may crank but not start or run unless you hold the accelerator pedal down 1/4". It will not give you the nice idle flare-up to 1,500 rpm's at start-up, and it will tend to stall at stop signs. This is all very different than when an engine stalls while you are driving at highway speed. That is an entire different set of causes and diagnostic steps.

You have to meet the conditions necessary for the computer to do the relearn for minimum throttle. Do that by driving at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals.

Do not get wrapped around the axle over either of those codes. I used to find them very often at the dealership on cars that were in for alignments and suspension work, and I had a reason to connect the scanner for other services. It had always been my belief that code 12 sets when switched 12 volts is lost, meaning the ignition switch was turned off. I was told by one of our other experts here that was wrong;... That it was related to memory power, so that is what I have been posting. I might have been right all along, or it might be different on different models. For example, cars that came without air conditioning would always have a code stored related to the compressor relay circuit being open, ... Because it was not there! When powering up the scanner, it asked if the car had AC. If you entered "no", it would not display that code. In the same way, Engine Computers on some car models might be programmed differently to need different requirements to set code 12.

I ran out to my 1994 Grand Voyager right now and I just checked the codes with the ignition switch. I am getting code 12 too, and my battery has also not been disconnected for a long time.

My assumption had always been that code 12 is useful when you are chasing an intermittent stalling problem. If you erase the codes with the engine running, code 12 will not set again until you turn the ignition switch off. Now, if you go on a long test-drive until the intermittent stall occurs, you can coast to the side of the road without touching the ignition switch. If you find code 12 has set again during that drive cycle, it shows the switched 12 volts had been lost at least long enough for the engine to stop, (or hiccup). The common suspect would be arced contacts in the ignition switch or two burned terminals on its connector. Regardless, at least you would know that is the circuit you need to be looking in for a wire rubbed through, a corroded connector terminal, and things like that.

Did you do the relearn procedure, and did it solve the stalling problem? Keep me updated on your progress.

I regularly run the battery in my van dead by using a power inverter. The engine always fires right up by using a jumper pack, but about one out of five times the idle speed needs to be relearned. I do not even think about it any more. On the way home, I have an exit ramp where I coast for about twenty seconds. That is when minimum throttle gets relearned and I never even notice a low idle speed problem.