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. car has 30,000 miles on it, it flashes CEL when driving but not at idle but yet is still misfiring at idle as well. CEL will go out after 30 seconds of mild driving even though it's still misfiring. 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 though. Any further suggestions to figuring out this problem would be great,

 

Well as it sounds like you're aware, compression issues can cause misfires (piston/ring failure, valve failure, or head gasket failure). Ignition and sensor issues can also cause misfires.

If the misfires seem to happen on the same cylinders, try moving the coil pack(s) to another cylinder and see if the misfire follows the coil pack. If so, then it's a bad coil pack. You can do the same thing with the spark plugs to see if it follows the spark plug.

The crank position sensor is also another possible area because sudden inconsistencies in crankshaft rotation that the computer sees are registered as misfires, and when detected in concert with noise picked up from the knock sensors, registered as knock.

Also, air or AFR metering issues, such as with the Mass Airflow sensor being dirty, Manifold Air Pressure sensors going out or having a bad connection in the case of the GM Stage 1 sensors, or the first O2 (wideband) sensor going out, can also cause misfires. The ECU and engine can be picky sometimes.

Our cars always target ~14.7 AFR, unless:
- You go wide-open throttle
- You let off the gas while above ~2,250RPM in 2nd-4th gear (Deceleration Fuel Cutoff, it'll peg 18+)
- You let off the gas while above ~1,000RPM in 5th gear (also DFCO)
- Sometimes during shifts, it'll cut fuel during the shift
- Catalytic converter cooldown mode happens, during which it will temporarily target ~14.0

 

what readings should I be seeing for MAF MAP and the wideband o2 sensor
as of right now my MAF is 0.67 TO 0.69 roughly and my MAP is 39 kpa

 

Also, check ur injector seals, those have been know to be missing causing issues.

 

Like lots of machine gun popping at mild boost.

 

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 ?

 

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

 

My car does the machine gun misfiring crap between shifts at high rpms

 

what are your plugs gapped at should be .032-.035 and how many miles on them should change them every 10,000 miles

 

i change them every 6k miles and they are gapped at .32

 

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

 

i changed my coil pack and still having them between 1's and 2nd shifts or 2nd to 3rd shifts at high rpms...changing my spark plugs again just to make sure its not them and my sensors have all been replaced other than the maf, but it is cleaned on a regular 3 month basis...