Alright guys, who can figure this out? 2007 Forester with 70K on it. Was running great until a few weeks ago when it started missing at idle (will run smooth, then miss once or twice then be smooth again) and sputters at low rpm under load. High RPM and WOT it is fine. Had a CEL for cylinder 4 misfire.
Hooked up the logger: IAT, TPS, MAF, coolant temp sensor, idle switch all seem to be working fine. Rear O2 was stuck at 0.85 at idle. If I stabbed the throttle it would cycle. I couldn't read the front O2 for some reason.
Already changed plugs and wires. Also swapped coil packs with a known good condition one.
Any ideas? Here are mine:
Injector: Only thing left I can think of that explains only having a problem on cylinder 4. Considering switching this injector to another cylinder to see if the code moves. Just need to buy new seals.
EGR: If stuck open, it could explain the rich O2 at idle, but I've heard it's rare to get stuck open, and it doesn't explain the cylinder 4 misfire. Considering swapping for the one off my wife's car.
Dirty throttle body: Heard it might cause this problem.
O2 Sensor: Not sure if this is the problem or if it is reading strange because there is another issue.
I would be grateful for any ideas. Don't particularly feel like throwing parts at the car/spending $100 on new gaskets to swap parts between this car and my wife's if I can help it lol
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