hey guys im new here and bought a 07 supercharged gm stage 2 a couple weeks ago. when i bought the car it had no check engine light but a couple days after the code P0300 popped up.. it was also getting like 14mpg!! changed spark plugs and fuel filter and mpgs went up to about 22 and check engine light went away. after a couple more starts it came back on.. the car has a really loud exhaust leak do you think it could be causing the random misfire? only thing out of the ordinary with the car is that when im at a stop and rev the engine it hesitates alittle bit.

 

Exhaust leak probably affecting the 02 sensor. did you get the right plugs?

 

Thats what im thinking but wouldnt that throw a rich or lean code? i got ngk iridium ix plugs gaped to around .38.

 

NGK coppers. .035.

 

Use the oem ones at I think .35 or .32 whatever they are for lsj

 

The spark plug sticky says the ngk BKR6E plugs around .38 are fine for an lsj with slight mods. So thats what i went for...

 

Yea and experience says copper OEM heat range plugs at .035"

 

Ahhh i read the sticky wrong... it does say copper plugs.. will be getting them shortly. Thanks

 

So i shouldnt go a step colder because of stage 2?

 

alright guys here's an update.. replaced plugs with stock copper ngks gaped at .35, fixed exhaust leak, cleaned throttle body, replaced a bad intercooler pump, changed oil and it smelled like fuel, held a screwdriver up to each fuel injector and each of them are ticking. code came back on. here is the freeze frame data on my free obd software.. lol.

P0300

Fuel system 1 status closed loop control using oxygen sensor - normal
Calculated load 25.9%
Coolant temperature 69 deg C 156.2 deg F
Short term fuel trim bank 1 3.91% Lean (-)
Long term fuel trim bank 1 1.56% rich (+)
Intake manifold pressure 41 kPaA 5.9 PsiA
Engine speed 766.25 Rpm
Vehicle speed 0 Kmh 0 Mph
Ignition timing advance cyl #1 11 Degrees Advance (+)
Intake air temperature 10 Deg C 50 Deg F
Mass air flow 3.92 g/s 0.5 lb/min



i dont know if this data helps but what do you think it could be?

 

Also i can feel and hear the misfire at idle when i come to a complete stop and also feel a random pulling/jerking when im on the gas sometimes.

 

Ngk bkr6eix is the stock plugs