Alright, I have a friends 05 R53 w/jcw package sitting in my driveway. I have finally gotten to a point of bewilderment that I'm hoping someone here might have some insight to.

So here is the symptom. Start the car from a cold start, warms up and runs strong. after running for a few minutes the car will stutter, DSC light flashes, check engine light comes on, and runs like crap. code reader has a p0300 code but thats it. turn the car off, and restart, car will run fine for another few minutes, then after a few minutes will repeat the same symptom.

Here is the diagnostic work I have done thus far. While the car is running and the symptom is present I popped the plug wires off and on one at a time and isolated the misfire to cylinder 3. Lets dig into known good parts I have stashed around my garage...Installed new plugs as the old were a bit used (not bad but lets eliminate the easy stuff first, right?) No change... replaced plug wires, no change... Swapped coil packs with a known good one, No change.

Unfortunately I dont have a known good set of jcw injectors laying around, so I pulled the fuel rail and moved injector 3 to cylinder 4. If the mis followed the injector, I know its injectors. Fire the car back up, and the mis fire continues.... on cylinder 2..... key cycle the car, and when the symptom returns it does so on cylinder 3....Now I'm lost, At this point I dont think its unreasonable to suspect the ECU.

Its worth mentioning here that, there was some work done to this car by a previous owner and I discovered 570cc injectors in place of the stock 380's. Neither I or the current owner know what else is done to the car, but it runs super strong. Without diving into the motor I would say I'm 95% sure it has a aftermarket clutch/lightweight flywheel, and possibly a cam. I know that bigger injectors were fitted from an SRT-4. and for that reason I'm sure it has seen a tune of some sort.

Any direction or ideas this wonderful community has would be greatly appreciated. I'm limited on what I can do in my garage as far as computer diagnostics are concerned, I only have a basic code reader. Could likely borrow a more advanced one from a buddies shop if needed.

 

Moving you to the Stock Problems/Issues area.

Try a dollar bill test, will give you a very good idea if you have a burnt valve.

 

Thank you for moving me to the proper area. I will try that test when I get home.

 

Ran compression test this weekend. Good compression across all cylinders. Pretty sure at this point I can rule out most mechanical causes.

 

Been thinking about this one. The head on the Tritec can develop almost micro like cracks around the plug hole. There are some threads here on the matter. I am wondering if you have these at # 3. Motor was cold/warm but not hot when you did the compression test?