P0300 Misfire Code

[Chrisrokc]

I have been trying to figure out this misfire problem for two weeks on my 2004 Corvette Z06. This is what I have checked so far.

Wires
Plugs
Grounding on the back of the driver side head, and on the block
O2 Sensors


I am lost now for the most part. Anyways here is a log from a drive the other night. Maybe this can ya'll help me figure this thing out.

http://files.me.com/chrisrokc/4qp5z0

I believe I started to encounter this problem after I installed longtubes. However, it is possible it was doing it lightly before hand. Nothing like right now though.

[blownbluez06]

Do you have a good multimeter? Have you tried measuring the resistance between each coil ground and a known good ground such as the alternator or vehicle chassis? Do that. Have your run a compression test? broken valve springs can cause it. If you have remote mounted coils, meter the coil chassis to the vehicle chassis for continuity. Turn the key on and verify good voltage to each injector and coil as well. Make sure every injector plug is fully seated and look at each connection to make sure pins haven't been pushed back up in the plugs. Have you pulled the codes? List them all even if you don't think they're related.

[Chrisrokc]

I will do some of that you listed off tonight. Hopefully I will come up with something good. One thing I did find is that the back bracket on the driver side is rubbing through the wiring harness for the fuel injectors. Haven't been able to check to see if it ate through the wires, but it needs to be looked at for sure.

Post my findings later.

[Chrisrokc]

Do you have a good multimeter? Have you tried measuring the resistance between each coil ground and a known good ground such as the alternator or vehicle chassis? Do that. Have your run a compression test? broken valve springs can cause it. If you have remote mounted coils, meter the coil chassis to the vehicle chassis for continuity. Turn the key on and verify good voltage to each injector and coil as well. Make sure every injector plug is fully seated and look at each connection to make sure pins haven't been pushed back up in the plugs. Have you pulled the codes? List them all even if you don't think they're related.

Ok, I checked the compression. Cylinder 7 and 8 look just like the others. All click off just under 180psi.

[da_vato]

did you ever fix this? If you havent pull your injector rails with injectors still attached get a clean clear container to drop all the fuel in, pull an injector at a time inspect each injector inlet for debree. Im sure youre gonna find more crap than you thought. Clean the dirty ones, and put everything back together. If this does not clear the problem the dirty injector most likely died.