The car started rough running with the check engine light on, the previous day it had been running perfectly.
I used the torque app and found the following DTC’s, P0300 multiple cylinder misfire and P0406 EGR valve position.
I removed the EGR valve cleaned it and soaked it in WD40 overnight. Upon reinstallation the car was still misfiring with code P0300. Looks like the EGR problem is fixed.
I decided to replace the spark plugs, plugs 2 and 3 were particularly tight so I soaked them overnight with Aerokroil (a really good release oil). They were still pretty tight but they eventually came out.
Upon replacement I still had code P0300 which changed to P0302 cyl. 2 misfire after clearing and running the car again.
I did a compression test and the results were. #1 190psi #2 190psi #3 185psi #4 185psi
I have confirmed from the condition of the plug that cyl. 2 is not firing correctly. My next course of action was to clean and swap injectors 1 and 2 and swap spark plugs 2 and 4.
After I had done this the result was the same #2 misfiring with code P0302.
Does anybody think it could be the coil pack? I have looked at the circuit diagram of the coil pack and as plugs 1 and 4 run off one coil and plugs 2 and 3 off the other coil leads me to believe it’s not the coil because cyl. 3 is firing OK.
The other information I can add is that there seems to be a sweet spot between 1500 and 1900 revs where the car doesn’t misfire.
Thanks to all of the contributors to this forum, your posts have help me a lot in troubleshooting this problem so far.