by hilljb » Mon Dec 28, 2015 11:39 am
I've searched around a bunch on here, and I think I may be down to a PCM issue.
What's going on: I drove from Michigan to Colorado for Christmas. I've noticed in Colorado for the past few months that the truck will hesitate a bit when accelerating from idle. The truck idles around 700-800 when warm, and it'll drop to around 400 or even lower before the truck seems to be on the same page as me and we move forward. Hasn't been a big issue, until I'm in Michigan and I start stalling when I hit the gas.
The throttle body was cleaned (removed, cleaned spotless) before leaving Colorado. The air intake bolts were tightened (they were loose). Air filter and spark plugs were changed. All of this had no effect on the near-stalls.
After reading on here, I tested the upstream O2 sensor. The graph seemed slow and there was a sudden drop in voltage when I hit the gas (when the truck nearly stalls). I removed the electrical connector to the upstream O2 sensor and the truck runs like a champ, but the check engine light obviously comes on (it hasn't been coming on until that) and I can't use cruise control.
So, I replaced the upstream sensor. I plug it in, remove the codes in the computer, and we're back to nearly stalling ... with a new O2 sensor.
At least I know I can unplug the O2 sensor and run if I need to. Does this sound like a PCM issue? I do have an original PCM in there and I'm not sure if the previous owner had any maintenance done on it.
Cheers, and Merry Christmas / Happy Holidays everyone.