Okay I own a 1996 Dakota w/3.9 Magnum. It has 139,000 miles on it. It will idle ok at first but as it warms up its erratic and stalls, backfires. I have replaced theO2 sensor, MAP, TPS. I have done the intake manifold plenum gasket reapair and Im still getting codes for the 02 and MAP even after resetting the PCM. I am at a loss in what direction to look or go in now. Your input wouldbe much appreciatted. In the past this board has been very helpful. Thanks in advance.

 

You didn't mention anything about the IAC. Try cleaning it or replacing it. And not with a POS from Autozone or the like. (Hope you didn't get the TPS there)At the very least get a Standard Motor Products one. And since the plenum was bad have you had the cat checked? And did you replace the plugs? They won't cause that prob. but normally when the plenum gasket is bad it will destroy the plug where it was leaking and the cat is not far behind , depending on how long the gasket was bad.

 

ZMan thanks for the reply. I have cleaned out the IAC as per instructions I found here. The cat I think at this point is definitely suspect the truck is fine when its cold as it warms up the sputtering starts. I have gotten under the truck and tapped the cat with a rubber mallet but it didnt produce any secondary noises as if the inside was coming apart. I pulled the plugs and replaced them with OEM parts - autolite. Thanks.

 

Cleaning the IAC or TPS for that matter, is not always gonna work. And like I said, don't replace them with cheap brands.

 

pay attention to the codes. i've learned that the pcm doesn't usually lie, and its almost always smarter than i am. what are your codes ?

 

The codes 12, 14, 21, 55 came up so I replaced the Map and o2 sensor. I looked past the butterflies and the intake was really filthy, the gasket had failed, fixed that. Replaced all plugs made sure they were gapped properly. If i had any hair left on the top of my head I would be pulling it out.

 

If you are getting codes for the o2 and map even after replacing with new units and resting the computer, the only thing it can be is wires. A loose or broken wire. Check all conectors make sure all are clean and dirt free. Check all wires to make sure no broken wires. If you have to get a meter and check each wire from the sensor to computer and power wires.

 

Ok just for kicks I put a timing light on it. I realize that timing is non adjustable on the 3.9.
So when I lit it up it showed roughly eight degrees before TDC. Anybody have an idea on what the base timing should be ? Thanks.

 

Hey Fellas, I got it. After checking everything I could and what you all provided I started over. I pulled/unplugged both 02 sensors. Guess what ? It ran like new. I dont know why but Dodge trucks must really hate Bosch sensors. Self induced trauma - AAARRRGGGGGHHHHHHHHHHHHHHHH !!!! I have now learned the ultimate lesson with the Dakota - It will only run as good as the parts you put on it. Thanks for all the input, this board has helped me retain my sanity. Tommorrow I will return the Bosch sensors since they are only two months old. The sense of relief is quite uplifting - here's to all of you - THANKS !!!