What brand crank sensor? If it's an aftermarket piece, replace it with genuine mopar sensor. I bet your problem goes away.

 

I have actually wondered about the sensors on the TB. I did have to replace 2 defective tps sensors. Both new out of the box. The crank sensor is just a rotation counter over time. It is either working or not. The others on the TB are variable and more sensitive to being made to a higher specification. I think that has more validity. Like I said before, so much speculation but no real definable solution. I think there is hage number of variables that create the same symptom of erratic idle, that it is just a pain to fix.

 

That's what I thought about the crank sensor as well, however, another member was doing some testing with an O-scope..... and he noticed the several cylinders had consistently weak spark. He replaced the crank sensor, and the problem was gone. I have also seen MANY instances of the 'mystery miss' caused by aftermarket crank sensors. So, while *theoretically*, it either 'works' or it 'doesn't', it seems in actual practice, that is simply not the case.

 

I can appreciate what you are saying. I will look into the mechanics. I would have to be convinced that there is a technical need for the the crank sensor to do more than synchronizing spark clock. It has always been my understanding that the intensity of the spark is not affected by the crank sensor. If the sensor is out of alignment or damaged, I could see the potential for an intermittent clock signal or a week exciter on the flywheel, causing one plug to not fire. The one thing that will set off the engine light is a misfire of a plug. This is one of those things that will probably surprise me. I actually scoffed at a post that told me to check my transmission fluid for bubbles or froth. At one point, The engine acted like it was missing and the vehicle would feel like it was driving through large puddles of water at high speed. It turns out that if the fluid is not at the proper level or has bubbles/froth, the fluctuating fluid pressure and torque would confuse the computers management of the transmission. I topped it off and that particular problem went away immediately.

 

And that is the exact same reasoning I used when chatting with the other guy. I am in complete agreement with you, that is how it *should* work. However, there is a fair bit of evidence to the contrary. These trucks simply do NOT like aftermarket sensors in critical locations.

 

On that, there is no argument! I can be absolutely wrong and happy. I am sick to death of this problem. I spent a week chasing rabbits on the bad TPS. (Only to find out the new one was bad too.)
One tends to get tunnel vision and start doing the same things over and over looking for a different outcome.
right now, if someone told me to use chromed Schrader valves on my left rear tire if I want my idle problem to go away, I would try it!

 

Ya just never know.... that might work.