eez

iTrader: (1)

so i took my z out for a run to do some data logging. Did a 3rd gear pull up to 6800 RPMS. At around 6800 I heard sputter so I let off. Shortly after a P0300 (random cylinder misfire) lit up solid and the car sounds like crap and is shaking really bad at idle. I have cypher so I did the cylinder test and shut down each one at a time to see if it cleared up, but that was not the case. The sound it's making kinda sounds like a really bad exhaust leak, but I assume that is from the misfire (I really don't know what misfire sounds like).

From searching I found the following to be causes of p0300 and most of the people that throw this code don't really notice the misfire. Mine is horrible and the car is sounds like it's hurting badly.

Any suggestions on where to start first? I haven't made an changes recently.

causes of p0300

Improper spark plug? fouled maybe, but all 6? Shutting down each cylinder should have pointed to this right?
Insufficient compression
Incorrect fuel pressure? I don't have a fuel pressure gauge...
The injector circuit is open or shorted
Fuel injectors
Intake air leak? Don't think this is the case
The ignition signal circuit is open or shorted
Lack of fuel
Signal plate
Heated oxygen sensor 1
Incorrect PCV hose connection

Jokestrap

I would check the coil packs and plugs first.

Gumpdriver

iTrader: (5)

I just had this problem, check your coil packs first.Is the SES light on

XKR

iTrader: (1)

++++1

eez

iTrader: (1)

yeah the ses light is on and turns right back on when i clear it. Thanks guys I'll check the coil packs first. Although if I had a bad coil pack/plug, wouldn't shutting down the cylinder affected stop the misfire? or no...

QuadCam

iTrader: (8)

check your plugs...

if you had a certain cylinder going bad, you'd get a specific cylinder misfire code...like a P0305 for cylinder 5.

eez

iTrader: (1)

it was the plugs, swapped them out and everything is fine. I really need to get a tune!!! The plugs look carbon fouled.

booger

iTrader: (6)

If you arent tuned now . There maybe a chance you broke a chunk of ringland off and it is stuck in the valve . Hope not !

Good luck !