The skinny: No trouble codes. Truck runs excellent afterwards.

The long: If I disconnect the battery, and then reconnect it, I seem to expose an issue the PCM is able to correct given about 20 minutes of idling.

Once I reconnect the battery and start it up, it seems to be running rich. The idle is horrible, very lopey, exhaust smells, a throttle snap can make it stall out and it'll be difficult to restart unless I give it some throttle while cranking. Long term fuel trims during this seem locked at 0, short term fall to the low teens, I've seen -14.

The video below is what it does once I've reconnected the battery. Engine is cold in the video. It'll run like this for 10 or 15 minutes before settling out and then it's fine forever, though LTFT afterwards are around -5.5, STFT bounces around +2 to -4 throttle dependent.


Any ideas on where I should start? Once it adjusts the trims it runs excellent. Great power, no more idle issues, and it'll remain good as long as I don't disconnect the battery. It does not appear to be affected by engine temp. It'll do the same thing hot or cold if I reset the battery.

 

Fuel trims being a little off after resetting the computer is normal. It has nothing to base its adjustments on. O2 sensor starts coming in to play after two to three minutes run time, as it takes a bit for it to warm up, and start actually working. Sensor 2 really doesn't matter, it just monitors the cat.

How are the spark plugs and such? I expect it to run a bit rich initially.... but not to the point that it stinks like gas.

 

Plugs only have about 10k on them, champion coppers. I know they should be off, but I don't recall them ever being "runs so poorly it stalls out" off. There's obviously some issue the PCM is able to correct out, though. If I can figure out what that is before it gets to a point where the PCM cant adjust for it, maybe I wont be left stranded on the road.

 

Finding it is going to be fun. Doing some data logging, as much as you can, before it drops into closed loop would help....

 

Final (Hopefully) update to this for future thread historians. The truck finally decided to throw a code, a P2175. Throttle Actuator Control System - Low Air Flow Detected. Pulled the intake off, found a dirty throttle body with a carbon ring probably 1 to 1.5mm thick around the throttle plate. Cleaned that and cleaned the intake air temperature sensor as well. Reset the throttle and it's good now. Good throttle response, no more idle issues.