miss fire under load

[justryan]

ok i have a 2012 1.4 with budget trifecta tune, intake and exhaust. it miss fires really bad in higher rpms its much worst when it cold. but it does not go away when at operating temp either. this happened about 3 months ago so i changed the plugs and coil pack. that seemed to fix the issue. side note my car runs lean the plugs i changed were not oem previous owner changed them but they were NASTY and my tail pipe is black. im thinking it ma be a tuning issue.

 

[$ub$onic]

Throw the stock tune back on and see if it stops. Wouldn't be shocked if it was a tuning issue.

 

[justryan]

i wish i had the stock computer to swap out im also getting bad mpg. i just need to order a bnr tune but been busy buying other non fun life stuff.

 

[NewZJ]

I had misfire problems and coil pack swap fixed it on my end.

Are your problems still occurring?

 

[justryan]

yeah i guess i worded that weird yeah im having issues again. pulled the plugs they all seemed to have maintained their gap but are already dark.

 

[NewZJ]

If you can get your hands on another coil pack to test. It's not inconceivable for the replacement to fail. I replaced mine at 25k miles so I don't trust them much.

You could also datalog it and have bnr/trifecta check it. Or you could read it yourself.

If your plugs are dark, it may be running really rich and that could be a failed o2 sensor (it would give you a check engine light if so). Or it could mean you don't drive the car very far very often. Only short trips would do that to the plugs too

 

[justryan]

no to the short trips but i have no codes i have a scan gauge and only get a cel when the miss is really bad and i hold it and it only says miss does not give me any specifics

 

[justryan]

Well I have no cell but I have a fuel pressure regulator code

 

[Greasemonkey]

fuel pressure regulator is a devil. i have not had one fail on a sonic yet. but, many of the other cars i get into our shop that have the FPR go out wind up pissing fuel into the cylinders. usually by sucking fuel into the vacuum lines. unfortunately, our (mine 14 1.4t) FPR's are electronic. so, theres no simple "test by checking the vacuum lines". i would go to a parts house, buy a FPR and a can of brake clean. change the FPR (ANYONE CAN DO IT!) if it works, problem solved. if it doesnt work, wash the new FPR with the brake clean, dry and return to parts house. with the plugs going black, the black tailpipe, i would say you are for sure overfueling. i would start with the FPR... just my two cents...