I recent had my engine rebuilt

Forged CP pistons +.5mm bore (9.5CR) + ZRP rods, during this time just about everything was replaced through FCP, sparks, coils, injectors, hpfp, etc. Added a highflow downpipe, an ebay intercooler, and AEM intake.

Recently car has been misfiring on cold start, varies from all cylinders for the amount of misfiring but happens most in 4. Once the car has warmed up misfiring seems to subside, and while driving it doesn't seem to misfire at all.

Car hasn't been tuned yet, been about ~6k miles since rebuild wanted to make sure things were settled and wasnt sure if there was anything else I wanted to have done before tuning.

At somewhat of a lost with misfires, seeking guidance.


Thanks in advanced

 

Any codes other than misfire codes? Compression numbers on each cylinder? N14 or N18? Model year? Has timing slipped since rebuild?

 

2009 JCW N14

normally there’s a CEL for P0420 but that was a given because of the DP randomly scanned it one day and saw there were a lot of misfires now I’m getting P0300 and codes for various cylinders misfiring

Compression test will be done tomorrow

Timing chain was swapped out <5k before the rebuild so the same timing chain was used. Unsure if it’s slipped since though.

Spoke with a tuner today and they said most likely it’s due to the stock tune

 

Which tuner is blaming the stock tune? Sounds like a sales ploy…

Have you tried swapping the coils around, to see if the misfire moves? New coils and plugs can have defects.

Was anything done with the injectors during the rebuild?

 

Are you 100% sure the car is not misfiring when running or warm. Have you looked to see the conditions when the misfire codes were logged. On my scanning stuff you can see the conditions when a code was thrown, rpm, throttle position etc.

Very important information. If it is truly only misfiring when cold and first cranked up, then that is a completely different thing to if it is misfiring all the time.

Having said that, it is hard to troubleshoot as so many things have been changed at once. Bad fuel is something that certainly comes to mind. Poor quality fake plugs is also something that has been a problem generally in recent years.

 

Yes swap the coil around and check plug gap or the type of plugs. Stock tune would not do that. The ebay intercooler could have issues in construction but its would not cause that. It might have a boost leak issue or not hitting full boost.

 

Random misfires at cold start. Gets a bit better warm. Reads like an intake leak air is getting into the engine after the MAF or MAP.

An old trick to find intake leaks was to use an aerosol can of carb cleaner. Spray some along where the throttle body bolts to the intake and where the intake bolts to the head. Cold engine likely it will react by running better but any reaction is a sign you have found the leak. And the rule is there are always 2 leaks unless there is just 1 or 3 or more...

Another thing to consider... Car has been sitting a good while. New engine with high compression pistons. Good gasoline is even more critical. I have to at least mention the gasoline could be stale.

 

I have the same problem...did you ever find out what was causing it?
https://www.northamericanmotoring.co...injectors.html

 

still stabbing at it, slowly… few things I think it might be in my case, one brake booster is leaking (smoke test proved), two leaky turbo, three piston rings not seating. My guess is the piston rings but I just don’t want to believe it because I am…. In denial

my issue is a little different than yours, mine would only misfire one cold starts, once it got to operational temps misfire stopped

 

ok, wow time to rebuild the engine with stout components. My misfire is only felt when cold but when warm it is not felt. I feel like building an engine with all new parts and be done with this one and I've not had any problems until now.