I have a 2003 1.8t, 140,000 miles. recently on a 200 mile trip it started to idle rought and the CEL came on. It read misfires on all cylinders and a lean code. I smoke tested it and found that the 90 degree elbow in the pcv system was leaking, fixed that, and it still is idling rough, but it didn't through the lean code any more, just random misfires. I cleaned and inspected the MAF, it seemed to be clean but i cleaned it anyways. that didnt change anything. I tried unplugging the MAF while it was running, still idles the same rough way. I'm at a loss as to what to check next. with the car running there is some suction on the oil fill cap, but nothing like what people say they experience when they had PCV problems. What possibility could cause the rough idle. Can a bad coolant temp sensor cause issues like this, how about o2 sensors. I plan on re smoke testing to make sure there is no more vacuum leaks tomorrow. i will also check the fuel pressure to see if the pump could be going bad. i really neeed some help with this one. thank you

 

You may still have a lean condition. Usually random misfire is due to a lean condition. You may want to check the fuel pressure.

 

okay, thanks. i was also thinking about the upstream 02 sensor, I'll ohm it tomorrow and see what it says but if thats bad could that be causing all my problems?

 

hmm i thinking more along the lines of coilpacks.

 

Me too... Just had the same problem and it ended up being a coilpack