I found a few topics similar to this, but nothing exactly. I have a 1994 Dodge RAM 1500, v8, 5.2 liter truck. A few months ago, I noticed that when it’s at normal temperature, it would not crank unless I floored the accelerator. Once it cranked, it was hard to keep it idling at a constant RPM. I have to rev it up a lot to finally get it to idle by itself or to put it in Drive to move. Once it’s moving, everything seems pretty good. If I stop and change gears (Park, for example), it will stall. I have also noticed this happening if I’m in Park, then turn on the air conditioning putting a load on the engine, it will stall.
When the engine is cold (sitting for several hours), it cranks fine and runs fine.
I have replaced the idle air control (IAC) valve, the throttle position sensor, the MAP sensor, the Crank sensor between the motor and the transmission (what a pain to replace), the O2 sensor upstream of the catalytic converter, and the computer (with a used one from a salvage yard. And, I had a mechanic check out the distributor cap and it’s internals and do whatever he did.
I did read somewhere that the coolant temperature sensor may be an issue?
I’m frustrated at this point. I’m running out of things to replace. LOL!
As a last resort, I replaced the coolant temperature sensor, and the stall/idle issues disappeared.
This weekend, my Dad pulled the connector from the coolant temperature sensor. Immediately, it fell apart in his hand. The top of the sensor pulled out of the bolted in part of the sensor. The sensor appeared to have two metal conductors soldered together. One of the conductors was still connected to the sensor, but the other fell off. We could definitely see corrosion as a factor in this sensor failing.
I replaced the sensor for about $20, and the problems of stalling/erratic idling disappeared completely.
Hope this helps others!
Thanks for the feedback. Most cars have two coolant temp sensors. One is just for the dash guage. The other is for the computer, the ECM. If the one for the computer fails, the ECM will not be able to figure out what fuel/air mixture it should be using. For an engine to run well, the mixture must vary quite a bit, according to coolant temperature. It looks like the way your sensor failed, it was reading the coolant temp was low all the time, even when the engine was hot. It thought the coolant was cold, so it needed a rich mixture, with more gas than normal. That’s why you had to allow more air into the engine when the engine was hot, to compensate for the extra gasoline the ECM was injecting, thinking the coolant was cold. Your solution should alos improve your mpg quite a bit. You’d think the ECM could figure out something was wrong and turn on the CEL, since it would know the engine had been running but the coolant never getting hotter, but I guess it couldn’t figure it out in this case. Good post.