Quick story: Got the PO300 random misfire code and after replacing the plugs and coils the car was idling smoothly with no code. When I was on the highway I decided to give it some gas to see if the problem was solved as it did fine otherwise. At 5000 RPMs it began to bog down and the CEL began flashing. Now it still has the random misfires. My next thought was fuel injectors but rather than tackling that I was wondering if anyone had any answers other than the ones I mentioned. The wiring to the coils is intact so it's either the injectors or possibly some other fuel delivery component. Any thoughts would be appreciated.

 

Have you checked out the FSM for your vehicle?

https://www.nicoclub.com/service-man...F2007%2Fec.pdf

See page EC-386

"DTC P0300 - P0306 MULTIPLE CYLINDER MISFIRE, NO. 1 - 6 CYLINDER MIS-
FIRE PFP:00000
On Board Diagnosis Logic NBS000RR
When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the crank-
shaft position (CKP) sensor (POS) signal to vary, ECM can determine that a misfire is occur"

Improper spark plug

Insufficient compression

If you did not use OEM parts and used cheap knock-off parts, you may very well end up paying again for the correct parts?

Good luck

 

P0300, I would start by inspecting the wiring harnesses for any corrosion or damage, was there any oil in the spark plug well tubes?

Pull and inspect all the plugs to see if you can tell which cylinder is the problem.

Verify the engine to chassis ground at the front of the timing chain cover isn't corroded, unbolt the lugs, wire brush the lug, the bolt, and the mating surface, apply a small amount of electrical anti-oxidation grease (not dielectric for spark plugs) and put it back together.

Clean up the battery terminals and lugs, also unbolt and clean the negative where it bolts to the chassis next to the battery.

If the problem still persists you might replace the ignition condenser, wouldn't hurt to just toss a new one in regardless since it's a $10 part.

Next go over the intake tract THOROUGHLY and look for leaks, a cheapo halloween fog machine works great but there isn't a whole lot to the system so you can also just pull the intake tube, visually inspect for any cracks/tears, the 3 PCV hoses should be tight and not able to turn by hand.

Clean the MAF with a MAF spray.

If that doesn't do it then it could well be a fuel delivery problem, start with a fuel sandwich adapter so you can get a pressure gauge on it. Z1 sells a nice adapter.