my 90 did the same thing, it was the temp sensor. the way i found out was the dealer hooked up their computer. you can shotgun it and go thru a lot of $$ but i would try to find somewhere to get it electronically diagnosed. also when it comes to sensors get them from the dealer or Napa, NOT auto zone type stores.

 

the coolant temp sensor or the air temp sensor?

I am guessing the coolant temp sensor, so i will go ahead and replace that (as well as thermostat since i have one to go in yet) and see what that does. If it doesnt fix it I will take it to shop to get diagnostic scan.

 

the coolant temp sensor

 

Cool thanks! I will update this thread once I install the sensor and see how it reacts.

 

Temperature sensor did not fix the issue. I guess Iwill call around tomorrow to see if any shops can do the diagnostic scan on it. Is it a special scan tool for this truck? Would I be able to get the correct scan tool and do it myself or no?

 

think it is more old school scanner based on a rolling cabinet. might be hard to find outside of the dealer??

 

I contacted a shop near my house, mentioned it was a 1990 dodge dakota 3.9L v6 and needed a diagnostic scan. They contacted me back and said they can do it Monday morning. We will see what happens I guess.

 

Well, it seems that the truck is running better today. I replaced the plug wires that I had to xchange for wrong ones the store gave me for the correct ones. I also replaced the thermostat. The first startup after the replaced parts it continued to do the symptoms while idling, but not even close to as much as it did before. I turned it off, accepting defeat and replaced the rear struts on my project car.

I took the bmw for a test drive with the new struts, all was good. I then decided to take the truck for a drive JUST to see how she reacted under load and whatnot. Miraculously she didnt stumble, hesitate, buck, or anything the entire drive. AMAZING!!! I then let her idle for awhile in the driveway to see if the temps would reach half since they never did before (stuck open thermostat) and they did.

Granted it was in the 60s today, but i think the wires might have done the trick. I will wait and see what happens when the temps get back down to the 40s and such. Will keep you guys updated.

 

Well, the wires did the job for about a week and now its doing the sane thing again, sometimes even worse than before. Its almost to the point where its undriveable. It will die in traffic now and sometimes at idle too. I replaced the dizzy pickup coil with no luck as well.


I looked under the truck at the transmission since it seemed to be the worse when the engine speed is at the shifting points. It will shift hard and up and down at the shifting points. The big sensor at the back of the transission is completely covered in oil and an wondering what that sensor is. Its got an electrical plug on it as well as a cable coming from it. Can anyone tell me what this is and if it could be causing my issues? Thanks in advance!

 

Sounds like the Crank Position Sensor is the piece you're talking about. Oil is very bad for them and sometimes can act up when they get hot (engine up to temp) when they are starting to go bad.