Definitely lean on that shop to get this right.
I have had similar adventures with this engine and it can be tricky to get it right. I have come to the opinion, I can't prove it, but from my experience this ECU is quite 90s level simple. It needs all the sensors to be pretty much spot on and can handle say one of them drifting rich / lean within limits and will correct via the O2 sensors. If too many sensors drift or are offset it only corrects so much (10-20%) and that's it. Thereafter the engine runs too rich or too lean. Too lean will cause spark knock which will be sensed by the knock sensors and cause timing retardation which will cause poor drivability, power, stalling... etc... I think the stalling is mostly the injector duration getting so small the spray pattern falls apart and so you get the stalling at idle with the idle control valve trying to manage it but unable to do so since it wasn't calibrated to manage poor combustion at idle. I might have mentioned many posts back, but my truck presently only runs well on 91 octane. 87 and it runs like a turd. I know my engine temp sensor is reading on the warm side and the AFM is 2 clicks to the lean so there you go. I just need to fix one of those to make the problem come/go to confirm my hypothesis.
On the flip side, too rich makes the engine run too cool which makes it more rich and it goes into a downward spiral that direction.
So, if you get time, can you get data from the Torque 2 app? Things like live O2 voltages, Vf1 voltages, AFM reading, engine temp would be good starters. We can cross check the shop and see if the collective wisdom of mud aligns.
Frank
I have had similar adventures with this engine and it can be tricky to get it right. I have come to the opinion, I can't prove it, but from my experience this ECU is quite 90s level simple. It needs all the sensors to be pretty much spot on and can handle say one of them drifting rich / lean within limits and will correct via the O2 sensors. If too many sensors drift or are offset it only corrects so much (10-20%) and that's it. Thereafter the engine runs too rich or too lean. Too lean will cause spark knock which will be sensed by the knock sensors and cause timing retardation which will cause poor drivability, power, stalling... etc... I think the stalling is mostly the injector duration getting so small the spray pattern falls apart and so you get the stalling at idle with the idle control valve trying to manage it but unable to do so since it wasn't calibrated to manage poor combustion at idle. I might have mentioned many posts back, but my truck presently only runs well on 91 octane. 87 and it runs like a turd. I know my engine temp sensor is reading on the warm side and the AFM is 2 clicks to the lean so there you go. I just need to fix one of those to make the problem come/go to confirm my hypothesis.
On the flip side, too rich makes the engine run too cool which makes it more rich and it goes into a downward spiral that direction.
So, if you get time, can you get data from the Torque 2 app? Things like live O2 voltages, Vf1 voltages, AFM reading, engine temp would be good starters. We can cross check the shop and see if the collective wisdom of mud aligns.
Frank
