doug1105

I'm getting the P0300 - Multiple Misfire and P0304 combo at idle.

I replaced all the even cylinders (passenger side) and still got the cylinder 4 misfire code.

I replaced the cylinder 4 wire out one more time for kicks, and still get the P0300 - Multiple Misfire and P0304 combo .


I started out and replaced all the even cylinders (passenger side) because I was originally getting a misfire code on cylinder 6.

All my wires are painstakingly routed through all the razor sharp black wire guides and clips.


Other Info:

The wires that were giving the original P0300 code look like new
Plugs are about 2 years old
All my wires are painstakingly routed through all the razor sharp black wire guides and clips.
Optispark is nice and oily/wet.
Front Cover is nice and oily/wet.
117k on the odometer

Injuneer

When you say you "replaced all the even cylinders"..... I'm assuming you mean you replaced the plug wires for all the even cylinders?

Could be plugs, injectors, sticky valve, bad lifter.... its not limited to the wires.

kingslam

and the OPTI ! how old is that?

Cook Performance

When you say you replaced all the even cylinders what all did you replace?
You need to check these items before you start thinking opti;
spark plugs- just because they look good does not mean they are firing.
plugs wires
spark at cylinder #4 wire
injector #4- one of the easiest ways to determine a injector is to check the resistance (ohms) if this does not reveal anything obvious swap out the #2 and #4 injector and see if the miss follows to #2.
the opti unit plays a major part in injector pulse aswell.
Good luck

doug1105

Before I even started changing wires, I was getting a cylinder 6 misfire code.

Since it's such a pita to route the wires in the stock locations, I figured I would just play it safe and just replace the entire passenger side set of wires.

That's when the misfire went to cylinder 4. I replaced the cylinder 4 plug wire with a different plug wire after that and still get the cylinder 4 misfire code. It it is missing pretty bad.

I changed the plugs when I put on the headers about 2 years ago, before that, the stock plugs looked fine. I don't think it's the plugs. (yes I'm going to check the plugs now)

I didn't see any arcing with the original cylinder 6 misfire.
I really don't think it's a sticky injector or lifter- but I'll check that now too.

sen

have a 96 z28 and just replaced all wire's and plug's wire's=oem plugs'= bosh p4 all have maybe 60 mile's on them now i have a p0300 misfireing code not sure where to start other than checking everything piece by piece anyone have any idea best way to go about this?

sen

srry post got put in wrong place