Random Cylinder missfire's
 

I have a 2008 cobalt ss tc and it has injen cai injen charge pipes mpx downpipe mpx catback exhaust. It is throwing a random misfire dtc. noticed the electrodes on my spark plugs are much lighter then they used to be. measured 65 psi before the fuel pressure regulator . did a compression test also. 165 psi across the board. Cleaned MAF sensor, noticed way high air fuel ratio's at higher rpm's but normal at idle, I believe idle should be at 14.75 to 15 but not positive. Any further suggestions to figuring out this problem would be great, thanks

how many k on the car, could be carbon buildup if its higher milage.

Flashing CEL or interceptor?

car has 30,000 miles on it. it is flashing CEL , but does not stay on all the time goes off after 30 seconds of mild driving

Try scanning it to see what cylinders and if there are any non-CEL illuminating codes?

first scan cylinder 4 misfire second scan multiple cylinder misfire third scan cylinder 1 misfire and there are no non-cel illuminating codes. also just got done putting in a stage 3 ky clutch could I have screwed up the crank position sensor ? also have a superchips programmer currently stock tho

This is gonna sound absurd, but if you're on the factory battery, replace it. Get a good battery, Duralast Gold, etc. No joke, that stopped by misfiring and I know that's been the solution to a lot of people's misfire problems on here.

My random misfires on all cylinders was caused by spark blugs. They were black is shit so I wirebrushed them, re-installed them, CEL gone, and car ran like a champ. Even got me 30mpg afterwards. Shifts better, idles better, breathes better and saves me money at the pump. Eventually replaced the old ones with new ones after O'reily's had to special order mine.

just replaced them a couple weeks ago gapped them to .035

been doing alot of trouble shooting the past few days and it
looks like its leading me to believe the MAP sensor is bad

its around 33 kpa at 20 vacuum
isnt it supposed to be in the 60's ?

Not sure. I gapped mine originally at .035 too but at a cold start I'd get stumbling and after I'd get on the road it'd be fine. So I tried .032 and that solved everything.

Oh and my car has 32,000miles as well.

this^

Is that at idle? Warm idle? I'll check my interceptor when I go out to lunch today

I had misfire issue also. Regapped new plugs at .032 and problem went away

yes that is at idle. and temp was about 100 degrees on car

was your misfire while making boost or at idle?


would a bad map sensor and or tmap sensor cause misfiring
also my map sensor has incoming voltage of 5 but no outgoing voltage. that calls for a new map sensor right? opinions would be great thanks

Have you checked your valves to see what condition they are in. I would take a peak and you will probably find them to be in pretty poor condition.

mine was at idle. p0300 everytime i started the car

33 is definitely good.. That's what mine is

it turned out just to be a damn coil pack ! at least that's all it was. thanks you every one for taking your time to give me input on this