Hey,
I’m having trouble diagnosing a misfire problem and am hoping to get some guidance.
First off – my car is a 2005 6MT RevUp with about 110K miles and it DOES have a pretty bad oil consumption issue.

My check engine light started occasionally coming on and when I checked the code it was P0300 – random misfire. After a while the light started coming on more often and then eventually it was constantly on and would blink sometimes. After checking the code again, it was still showing P0300 as well as P0304 – random misfire on cylinder #4.

I decided to try changing the all the plugs and also replaced the coil on cylinder #4.

All the plugs looked good except for #4 which showed huge carbon buildup (see pic). Proof that cylinder #4 was definitely not firing properly.


After changing all plugs and replacing the coil on #4 I am still getting P0300. I’m not driving the car right now so I’m not sure if this would evolve into a P0304 like last time.

I decided to do a compression test.
Here are the results on a warmed up engine:
1. 165 psi dry
2. 170 psi dry
3. 170 psi dry
4. 150 psi dry
5. 170 psi dry
6. 170 psi dry

The results are about what I expected for a 110K motor. #4 is low but still close enough to the others.
When I performed the test "wet" all cylinders were between 230 and 240 psi (I guess this means my rings are done which explains the oil consumption issue. Does it matter how much oil you put down the cylinders because I feel i may have squirted too much down them during the test)

One thing of note is that the “new” plugs have only about a couple miles on them and maybe about 30 minutes of engine idle time on them. I noticed when removing the “new” plugs to do the compression test that plug #4 still looked brand new like it hasn’t even fired (see pic 2). So either there’s no spark getting to #4 at all, or maybe no fuel is getting into the cylinder so there’s no combustion.


Any ideas on what to check next?
What’s the best way to check for spark?
What’s the best way to check if that injector is working?

Any help would be greatly appreciated. Thanks.

edit: also forget to mention that my spark plug tubes and the ends of the coil packs were completely dry with no traces of oil, so my valve cover gaskets are still good (one piece of good news )

 

I'm having a similar issue so I would like to hear thought on this as well.

 

I had similiar issues that required a new ECM to fix the misfire.

 

Update: checked for spark. On coil #4 and it seems to be working fine. So not sure what's going on with that cylinder. Maybe the injector? Hopefully the ECM isn't done like HotRodG35 mentioned.

 

Was it the ECM