Expert: Don Berlan - 6/23/2010

Question
The car has around 83k miles, I've taken the car to a mechanic a few months back and he pulled the codes as P170 and P173 only.  So I changed the O2 sensor on passenger side and MAF.  Thinking this would clear the SEL.  when it did not, I got my own OBD2 reader.  I found the P170 and P173 along with P300, P305, P306, P307, P308 I cleared the errors to see what errors would come back, and when the SEL came back on, these are the errors showing now, multiple misfires on cyl 5,6,7,8 and P300 (repeat)10 errors showed back up.  So I changed spark plugs and ignition coils from cyl 1,2,3,4, and put them on cyl 5,6,7,8. to check and see if the misfires would follow.  I cleared the codes again, and when I rev up the engine to 4000rpms, the errors came back. I'm still getting the same error codes on the same cylinders 5,6,7,8.  Don't understand why only on the right side cyl?  What would cause misfires to just those cyl.?  I would think a vacuum leak, or fuel pressure regulator would cause all cyl. to misfire.  I'm at a loss of what could be causing the problem.  Please help.
-Apollo.

Answer
A fuel pressure test would help to determine if there was a fuel issue.Have you replaced the fuel filters?this could cause a lack of fuel getting to the rail.Check also the injector pulse of the cylinders in question.You may want to check the spark plugs on that bank it would the condition of the plugs could tell you how the cylinders are firing.