Hey guys,

Thanks for your responses. I installed a new MAP sensor yesterday ( the updated version with the tiedown strap ), and while it was idling on the second driving cycle (less than 5 miles)...the CEL came back on. So unfortunately, the new MAP did not fix the problem.

For the next step, I plan on getting a valve adjustment this weekend. Hopefully, this will fix the CEL issue.

Also, for the questions above:

I have been constantly getting the following CEL codes:

P0300 to 0304, P1399

All 4 cylinders have been misfiring at some point, and the random misfire is also thrown.

I have tried swapping the same coil packs to different cylinders, but all the cylinders still throw the misfire code. Do you think it is possible that all the coil packs could go bad at once?

 

Instead of buying snd throwing all these parts at it which doesn't seem to be helping you, why don't you take it to the dealer and have them diagnose it and then fix the problem yourself? Sounds like you've wasted time and money. Just a suggestion.

 

Richee,

I agree with what you are saying, but I figured this method could help me save money on diagnosing and labor costs from the dealership. From what I read on other threads, dealerships will go through similar steps to "fix" the issue.

When I first encountered the dreaded random misfire CEL, I took the car to a mechanic and he recommended the spark plug TSB. After that didnt work, I tried to do my own research on this problem. I was thinking this was a simple fix because the engine runs fine during my drives.

If the valve adjustment doesn't work, I will probably end up going to the dealership.

 

The problem is fixed!!!

Thanks for everyones help. A mechanic friend helped with a valve adjustment over the weekend, and the CEL has not come on again (with 200 miles of driving).

During the VA, a few of the valves were out of spec. The biggest issue was on cylinder 1, one of the exhaust valves was very tight. The minimum gap range wouldnt even fit. It took a few hours to finish, but the car runs a lot quieter, and there are a lot less vibrations from the engine.

Once again, thank you everyone for your help. UTH has provided me a lot of great information to help debug the problem.