Hi all,

My 2004 v6 6-spd randomly had the CEL start blinking and threw 15 codes last night during the middle of a drive. The engine started running rough at all times (slight vibration, obviously throatier sound to the exhaust), but performance did not seem to suffer. Acceleration might be slightly worse, but it could also be in my head.

The codes were the infamous P0300-P0306 codes plus other codes relating to the A/F sensor and O2 sensor (I would suspect MAF sensor might be a possible culprit as well).

Anyway, I'm looking for advice on what to check before I bring this to my mechanic. Here's a list I've got going so far (all ranging from extremely easy to pretty easy):

Check oil level
Check fuel cap
Check spark plug gaps and coil connections
Check Cyl3 spark plug for oil (long story short, one of the gaskets from the valve cover is a little iffy over Cyl3)
Check MAF, O2, and A/F sensor connections
Check air filter
Check for exhaust blockage
Replace air intake tube (the one between the intake box and the throttle body has a rip in it)
Replace fuel filter (I'm due)

Anything else I should add to my list that is easy to do a quick check on? I've got a 25-mile drive to my mechanic, and I'm not wanting to make that drive with misfires if I don't have to. I don't want to add cats to my list of repairs.

 

The fuel filter is not easily accessed (part of the fuel pump/sending unit assembly in the gas tank), and is not required maintenance. Put some duct tape on the air tube, until you can get it replaced. If the oil gets high enough in the spark plug tube, it can cause the plug to misfire (get the gasket changed). If you can get the engine to misfire at idle, remove the wire harness connectors from each coil, one at a time. If when you unplug a coil there is no change in how the engine runs, you've found the affected cylinder. Good luck

 

What are the specific codes besides the mis-fire codes (P0300-P0306)?

 

FYI, I posted this yesterday at work, and when I went home I was able to knock off a few items from my list. When I pulled the coils, there was oil in cylinders 3, 5, and 6. 4 was clean, and a I didn't even bother to check 1 and 2 because they're harder to get to and the problem was obviously widespread. It looks like the gaskets from the valve cover are incorrectly seated. They're new, so I'm assuming they're not bad.

Step 1 is going to be to get that situation fixed and get the oil out of those spark plug tubes. Since I was the one who screwed it up in the first place, I'm bringing it to my mechanic to solve the problem. I'll keep this thread updated as progress is made.

@lazlong - It was only one other code, actually, I was wrong about that. It was P2197 (A/F sensor), which may or may not be related to this because my car has intermittently thrown P2197's since the day I bought it.

 

The spark plug tube seals are easy to damage while installing the cover. The wire harness over the rear cover doesn't help. I was successful on the second try, after adjusting the valves the first time.