Hi all,
I've been feeling a slight shake at idle so I plugged in my scan tool to reveal occasional misfires, only in cylinder 4, at idle or when load drops, i.e. when letting off the throttle. They're very slight, maybe 2-4 per 10 seconds. Not severe enough to set any DTCs. No other DTCs stored. Runs great otherwise, no knock or misfires at WOT. Stock.
Not a huge worry, but I thought I'd see if you all had any suggestions.
What I've replaced with brand new AC Delco (unless noted otherwise) components over the course of working on the car for other things, and/or swapped with known good parts from friend's car, and/or confirmed working from scan tool measurements:
-MAF
-IAT
-TPS
-MAP
-no vac leaks: all new silicone vac lines, including digital climate control line, and fuel trims between -12 and 0 at idle depending on whether car is warm (is the -12 normal for warm, long idle?)
-ICM
-ZZP Gen 4 wires
-Autolite XP606 plugs, .060
-coil packs
-compression: ~160 psi in all cylinders, dry, and all within 5 psi of each other
Thoughts of what it could be:
-leaky injector?
-partially clogged cat? or would this only manifest at high mass flow?
What do you all think?
Thanks for your time,
Komrad36
