Hi all, my dad has been fighting a cylinder 6 misfire for a while now on his 05 srt6. He passed away about a year now and now im trying to figure it out so I can sell the car. It has just under 30k on it and has the following mods that I know, Needswings intercooler, intake, and supercharger pulley. The shop that was working the the car put new plugs all around, and coil packs and wires on cylinder 4 and 6. They said its likley the tune causing the misfire. I am not sure if its tuned and if it is by who. When I went to start looking into the car I had to replace the rcm so it would start. The car seems to idle fine and run ok on light throttle and easing into boost, but once you get into boost somewhat quickly the check engine ligh comes on and has a misfire and stays around. I cleared the code and seem to be back to normal but I drove it again and got into boost and it misfired again. I have alot of maintenance records on the car, since my dad has owned it for 10 plus years. I am trying to figure out what I should do, or a shop in maryland that knows these cars. Thanks and all help is appreciated, David.

 

I'm assuming you get DTC P0306? Are there any other codes??? Also assuming the replaced RCM is new?? If not that could be a problem.
1. check the ground just in front of the battery, It is sorta under the fill tube for the window washing fluid is clean with good connections. There are four brown wires connected to the fender there. It is a ground for most things Power Train Control.
2. Look back through your records and be certain the Crankshaft Position Sensor is a Bosch.
3. Under the car there is a inspection plastic on the "bell housing" that allows inspection of flywheel/flex plate. The CPS gets its signals from the flex plate. Hopefully it is clean.
Those above could effect any knock signal, but with yours always specific to the #6 cylinder you should consider moving #6 injector to a different cylinder and see if the knock DTC follows the injector. Pull the plugs on #6 looking at their condition and inspect the cylinder with a bore scope. Gape on plug should be .040. While plugs are out check compression on #6 cylinder.
4. There is one knock sensor per engine side and they are hard to reach.
5. Electrical diagnosis gets involved and more than can be described here.
6. Make sure the serpentine belt isn't slipping.
GOOD LUCK.

 

Now THAT is a good list of items to hit for such a complaint. I see so much bad technical advice on here, it sure is good to see someone post who understands what they are talking about.
My only comment would be that I don't think the RCM would do this, altho the failure rate of RCMs is so high it's not a bad idea to mention it.

My only "add" would be that a "cylinder 6" misfire is NOT a 100% guarantee that number 6 is misfiring (you kind of implied that as well), the ECU interprets input from the sensors and concludes what 'must' be happening, but this is not always correct. With ANY misfire, I'd be quicker to accuse the Crank or Cam sensor than anything else just because those are inexpensive sensors, easy to replace, and they are CRITICAL in the operation of the ECU.

 

Thank you for some really good info, the Rcm is new that I replaced. And the only code is p0306. I’ll start working on this list and see what come out from it I appreciate the input!

 

I started off with the basics and just swapped over the new aftermarket coil the shop put on to cylinder 4 and the misfire moved to that cylinder. Something so stupid that 2 shops couldn’t figure out but the car is running great now, I have to clean it up and get it listed. Thanks for the input!

 

Makes you wonder where the shop got that #4 coil they installed. Moving coils is a lot easier than swapping injectors. Good to hear the problem is solved and thank you for getting back to the forum with your solution. Good Luck with your listing!

 

I wonder the same but thank you!