Hello everyone,

I have a 2000 Dakota with 3.8L engine

Problem:
Poor engine performance on hot restart of engine. Rough idling, poor throttle response and backfiring. Problem only appears when the engine is restarted after being turned off for 15-20 minutes and is cooking under the hood for a bit. On restart of engine, and under load, it will begin idling poorly after about 30 seconds to 1 minute (presumably when it goes into closed loop?). The engine starts to run rough and almost stalls. When I give it gas, the throttle is non responsive and engine will stumble and will start backfiring! 100 percent solution: Problem is always fixed when the engine is shut off and immediately restarted a second time when hot. Then the truck runs smoothly again for the rest of the trip. WTF?? Problem never happens when the engine is started cold.


This problem has been ongoing for several years now. I've had to to my local mechanic a couple times and to the dealer with little success in finding the cause. Maybe someone here will have some suggestions.

Troubleshooting to date:

No Codes present

plugs, wires, cap and rotor have been replaced

TPS has been replaced with OEM unit

O2 sensor (driver side, downstream) replaced in 2016.

All other 02 sensors have never been replaced

Fuel pump replaced


I think my next course is to replace all of the 02 sensors but I would think that a code will be present if they are out of range?
Thanks for looking.

 

O2 sensors have many failure modes that won't set a code, slow/sluggish performance, or simply reading wrong.... (too rich, or too lean) and the PCM doesn't have a clue, so, no codes.....