Misfire

[Byronator]

I currently have a misfire that first became a thing a few months ago. I have a small code reader and it said cylinder six misfire. I checked out the spark plugs and they are all fine. I tested the coil pack by leaving the wire unplugged from it but setting on top near the plug and watched the spark flow from the coil pack to the wire. So I don’t believe it’s a spark issue. I did a compression test and all the cylinders were a little low. With cylinder six being the worst they all ranged from 150-164ish. I did a “glove test” on my radiator to determine if the head gasket was bad. Nothing happened with the glove and the motor oil was not milky or nothing. I decided it was my valves causing this issue and bought reman cylinder heads and replaced my heads. I just got it all back together today. It’s running fine as far as I can tell but the misfire is till there. I did do some research and I asked questions on the forum before I made my decisions. But I ended up wasting a lot of time and money anyways apparently. I haven’t done a second compression test yet as I don’t own a “tester”. What could be causing the misfire? Could it be injectors? Thank you in advance for your time and reading this.

 

[Slothe87]

I'm going thru the same thing, but cylinder 4. I replaced Ignition coil, spark cables, spark plugs, and injectors. Still getting code.

 

[cbxer55]

I'm having the same trouble with a 4.0 Mustang. It's a P0300 Random misfire code. That means it's more than just one cylinder. Replaced coils, plugs and wires, checked fuel pressure which is good. Maybe it's an injector issue? Running some fuel injector cleaner in it currently. One thing I've noticed is that originally the code popped up pretty quick after clearing it. Now, it's been a P0300pd code for four days. It's taking longer to go from a pd to the check engine light coming on. So maybe the cleaner is doing it's thing.