Hey everyone new to the fourm, try to keep it short for yas but picked up a 2001 dodge dakota 3.9L 4x4 other day. Ran great for few hours the first day.
next day went for a drive and once it warms up it started sputtering and backfiring real bad and has a very rough idle and dies sometimes. Ive done a few things to eliminate the problems new battery new engine relay cleaned and checked the grounds and the tps on the driver side of tb and the idle control valve i think it is called thats on the rear of the tb. Ran fuel system cleaner through it aswell.
checked codes and it has 3 comming up 2 are for o2 sensor bank1 sensor1 shorted to voltage and heater circuit low. (Trucks still runs the same and has same problem even with it unplugged so i dont believe this is the cause)
the 3rd however is p1391 intermittent loss of crank position sensor or cam position sensor. Witch i believe could be the issue?
just seems weird how it only has the problems once its warmed up. The truck fires right up and runs perfect when its cold and for about 3 or 4 mins of driving. Then the sputtering and loss of power starts follwed by backfiring shortly after.
Is there any way of checking forsure that it could be the cps causing this problem. Ive been reading several fourms and this seems to be rather commen in the 3.9l anyways would love to hear some input on the problem! Things i can check or try to rule out. Really hoping its something stupid or easy to fix like a sensor and that its not an internal issue. It also came with a spare computer and i tryed it aswell and still nothing. Let me know your thoughts on the problem thanks alot! Backroadbandit

 

Pulled the plugs and cap of and cleaned all the contacts. Checked the cam positioning sensor and everything seems to be fine. Still has the same issue. Any input or help would be greatly appreciated!!

 

I may be wrong, but if your O2 sensor is shorted out, it won't be sending a signal to the PCM, or the signal will be a flatline. Unplugging it wouldn't change the signal that the PCM is getting, therefore no change to the outcome.


By your description of the problem, it is running good in open loop, when the computer isn't referencing the O2 sensors, but when it switches to closed loop and starts to take input from the O2's, it runs crappy.

The computer reads the CPS signals the same in open loop and closed loop, So it is not likely that the CPS is your problem. Or it's secondary.. Not the main cause.

I would be trying to find the short on that O2 sensor and fix that first. I would unplug it and test for voltage at the plug as a starting point.