I am a newbie SRT6 owner and it only has 36k on it.

I am getting error code P0303 Cylinder 3 Misfire. The two times that the car has ran ruff and I received this error was after the car had been sitting for only a couple of hours so it wasn't when it was completely cold. It started fine, then after I was moving it starts to run ruff, I pulled over and turned the car off both times restarted it and it ran fine. The check engine light does come on and stay on.

1. How do I identify cylinder3?
2. Can anyone recommend an ordered course of action to help me troubleshoot and fix this?

Thanks
Steve

 

P0303 is cyl 3 misfire & raises the question of "which is cyl 3 ?" since Merc uses odd cyl numbering.


Once that is sorted there are three things that usually cause a 303 (which is basically that the engine slows down when #3 is supposed to fire):
1) mechanical - e.g. a burned valve - rarely heals
2) fuel - clogged injector (high engine speed & high load)
3) bad secondary ignition (low engine speed, moderate load) (coil, wires, spark plug)


I'd probably pull the spark plugs and take a look first.


ps if misfiring I use an IR temp gun to determine which - the bad cyl will have a cooler exhaust manifold.

 

Thanks so much for the info!!!
I see that pulling the plugs is no easy task in itself

Is there no other way to determine which is Cyl 3? It would be so much nicer to be able to target the problem cyl and look at the plug, coil, etc and go from there.

 

See post #2 in this thread - it might help:

https://www.crossfireforum.org/forum...umeration.html

 

Cylinder numbering.


Todays deep question.
Why are there no fat stick men?

 

Thanks again!!!

 

Nice pic, thanks!!!

 

There are 3 ways to change the plugs :
1. the HARD way : dive in and expect substantial skin loss.
2. the STANDARD way : release the coil packs and fold them out of the way - expect moderate skin loss.
3. My way : remove the valve covers - expect NO skin loss.

 

That is a good picture of the MB numbering system. My question is "Does OBD-II follow the MB numbering ?" e.q. is the #3 cyl indicated in P0303 the passenger rear (MB) or passenger center (Chrysler), or... ? That is what I do not know.

 

The OBDI doesn't determine what is printed out, that is determined in the ECU so if it says cylinder 3 that is the correct cylinder'

 

That would be a good answer if it was a Mercedes and not a Chrysler ECU (which may have needed tweaking to meet US specs).


The engineering answer is to bypass the spark plug on "#3" and see what code sets.

 

Wow.....that answer is scary wrong. A OBDII compliance means exactly that. The ECU is compliant to communication with the scan tool software.
YOU should know that if you are giving answers and advice here.

 

And someone else who does not read what I write. Said I didn't know and suggested a way to be certain. I have seen automotive computers (mostly ABS units) lie before so trust nothing and try not to make assumptions.


Are all kinds of cylinder numbering systems & I have not found which if any is specified by OBD-II. In many cases it does not matter but for a P0303 it does.


Just learned a long time ago to assume nothing particularly since there was a phase in my life where if I made a mistake someone else made a large smoking hole in the ground. When dealing with computers being a bit AR is not a bad thing.


Also know that MB is a bit of an oddball with #3 being the rear passenger (LHD) side cyl and not the center like on a Chrysler. Buick V6 (also 90 degree) is oppo.


ps if I am wrong please state what is right with a source.

 

Computers do not lie, they are not smart. They do what they are programed to do. Bad code or failed components they may spit out rubbish but they did what the available input caused to happen on what was available.

I had a code set which said my problem was in the left front wheel speed sensor, it actually was the rear left speed sensor. That same thing had happened here before to another member, so someone somewhere made an error that affected scanner programs and the printed sheet of DTCs. Or did they, maybe some conflicting inputs caused the wrong readout, who knows. I do know it cost me much agro and $400.

 

Update......I installed a new coil on Cyl 3 per the pic on Friday and could immediately tell the difference, idle seemed better and no misfiring since.

Thanks for all of the suggestions........

 

Who told you that ?????