Well....going to bring this topic back from the dead. I bought Waterdog's car which is in great shape other than this misfire.
One thing I noticed when driving it is that the AC does not work. Looked at his DTCs again, and it has blend door codes. Since these are vacuum driven(At least I think they are), could a vacuum leak in the passenger compartment be causing this? I would think a vacuum leak would cause random misfires across all cylinders, but perhaps the lower compression on 4 makes it more susceptible?
Its been raining here nonstop since I got the car, and its supposed to continue through the weekend. Going to try to find some time to investigate.
Whats the best way to check for vacuum leaks in the passenger compartment? I can do a visual and also pull the hoses, but not sure if that will be sufficient.
Thanks in advance guys.
On a side note...my two Regals are the same color. My kids, twin 16 year olds, are now claiming they are their cars. lol They have a lot to learn.