So, basically I am the sole owner of an original (first day/first year) 03 Coupe with about 84,000 miles on it (its an Automatic). Anyway, I took it to the dealer for just a basic Mobile 1 oil change and also had to get a "control arm" replaced.....very expensive.

A day later, I am driving around and my Check Engine Light (CEL) came on and my NAV reported something about "emissions system". Anyway, I took it back and they claim my car reported a "cylinder 4 misfire" and they replaced the spark plug. Again, I drove it a couple of days and the light came back. I then went back to the dealer and they said it was the coil pak...so I replaced that.

A couple days pass (keep in mind that I've already spent over $1000 for new control arm, spark plug, and coil pak)....and the dang light came back on!! Argggg..... so now I am not sure what to do? Usually the dealership has been always great at diagnosing issues, but this time, they are failing big time! I am getting annoyed that each trip (which is 180 miles round trip for me) they swear that what they are doing will fix the problem.

So if any of you get random CEL coming on, and you've done similar repairs that I have done, please advise what could be causing the issue. I appreciate any help with this...as its driving me nuts!!! Also, i've noticed a few times the CEL will just go off, but later on come back on randomly during an engine start.

Thanks!

-Zeromus

 

First off, Call the stealership and tell them they suck ***** for not fixing the issues for CEL. Did you replace all the spark plugs or just one?
Get an OBD II code reader and get the error codes or head to Autozone and have the use their code reader to get the error codes. Also AAMCO, does free check engine light check. Research the codes at this link: http://engine-codes.com/make/infiniti

I recently had my CEL light on due to a dirty air filter and throttle body. Recharged my K & N and clean the throttle body and did the ecu reset procedure/idle relearn procedure and tada no CEL.

 

@lostangels01: I just replaced the one spark plug (cylinder 4) and the coil pak....

I can certainly have another read-out, but so far the code has always been "Cylinder 4 misfire) Thanks for telling me about AAMCO....didn't know that! I had spent a rediculous $80 to the stupid dealer for just the diagnostic

If its just a dirty filter or throttle body, then the freaking dealership really did rip me off... and this dealership I went to has usually been legit/honest in the past. Guess during these hard economic times everybody will nickel and dime.

 

Oh ok. Yea get a code reader or go to AAMCO. If you live in SoCal, AAMCO in LA on Melrose Blvd by the 101 is decent, they do a thorough check of your car for free if you have the CEL.

 

If you keep getting a misfire in that cyl even though you have a new plug and new coil pack, I would suspect faulty wiring or bad ECM

 

another thing to try is swap two coil packs and see if the cyl misfire happens on the other cyl now. You might have a bad ground causing the pack to fry (check the packs unusual deformation).

 

Whoa brother talk about having the same freaking issue

I keep on getting P0304 code

changed plugs
swapped coils
changed pvc valve (dunno why but it was cheap)
add fuel injector cleaner

Only cylinder 4 is misfiring and everytime I take out the spark plug is covered in oil and the tip is BLACK.

I ordered a new valve cover and will get it fixed this week. Will let you know if that solves anything, I doubt it

 

Also do you notice white smoke from the exhaust? I had my local guy take a look and he sent it to an 'expert' who said that it is probably the piston rings going bad and that = a BIG problem

Lets hope the two of us together can fix this damn problem. I guess we should each get different things looked at to see if we can determine the cause lol

 

Valve covers were a no go. Mechanic said the misfire is most likely related to an stuck/open valve on cylinder 4. He did a compression test and # 4 came in at 30psi which pretty much means that cylinder isnt firing at all. Not real fix besides a complete engine overhaul and so now I am looking for a used motor.