'06 Grand Cherokee V8 rough idle and erratic RPMs
I love my V8 to death, but it started having some idle issues and general loss of power around 4 months ago.
It all started the day after I replaced my AC blower motor and resistor. The next day I was sitting in terrible DC traffic, probably idling for about 3-4 minutes and when I went to press on the gas I realized that I had completely lost power. It wasn't idling rough or anything--it just went quiet. The radio never stopped playing, so it can't be a battery issue. This happened again the next day after idling for about 3-4 minutes. For the next two weeks it was sluggish and just felt like I was basically coasting everywhere.
I took it to my mechanic, but they couldn't recreate the problem. No codes, no nothing. Auto zone tested the battery and the alternator and everything checked out fine. I kept stressing that my RPMs were outrageously low for what I was used to. As soon as they dropped below 500 it threatened to stall out.
I ended up taking matters into my own hands and I replaced the spark plugs (some of the old ones had melted down), the air filter, gas cap, dumped a can of seafoam cleaner in the gas tank and I would have replaced the fuel filter but it isn't accessible. The dealership also reflashed my PCM. I could definitely tell a difference power-wise after doing all of these things but I was still idling at around 500--sometimes 600 RPMs on a GOOD day.
The jeep seemed to pep back up until a couple weeks ago. I was starting to idle rough, shifting seemed a little off, and it was driving kind of rough even on the highway. Now when I idle the RPMs wiggle up and down between 600 and 300. I started shifting it into neutral to raise the RPMs but they dance there too. Now when I'm in park they'll drop down to 300-400 and then rev up sometimes to 2,500 over and over again.
In attempts to fix it I replaced the Idle Air Control Valve (the old one was completely black) and the throttle position sensor. I've driven it about 150 miles since and it's shifting better overall but the problem still persists. I've been warned by multiple people about cleaning the throttle body out so I'm a little hesitant but at this point I'm getting kind of desperate.
What does everyone suggest I do next? I was planning on going ahead and replacing the PCV valve and at some point I'll probably replace the fuel pump assembly.