Hi Everyone,

I've been desperately trying to fix an engine misfire for a few months and I've ruled out most of the usual suspects. I'm at the point where the next steps will probably start getting expensive so I wanted to check here to see if anyone has any thoughts on it.

Several months ago, I was camping in Wyoming and noticed a slightly rough idle but no loss of power or a check engine light. On the drive home the check engine light came on but still had full power. I cleared the faults and drove it until the check engine light came back on and looked at them again. Ive attached the list of faults, but the most significant ones were a gross evap leak, cylinder 5 misfire and a downstream O2 sensor voltage fault (P0137). The engine was still running pretty well, so I grabbed a bottle of BG44k and ran it through to see if it was just a gummed up injector causing the problem. That didn't work, so I started down the list of easy fixes since I was really busy with work at the time. Long story short, its been about 4 months and the problem has gotten much worse (power loss and very rough idle) and it consistently throws 60 faults when I check it with my IID tool. It shows that every cylinder is misfiring and on the rare occasion that only a few faults show up, they aren't always cylinder 5 and they are usually on both banks. Here is a list of what Ive checked/replaced so far:

1. BG44k
2. Replaced Gas Cap
3. Replaced Spark Plugs
4. Checked coils and wiring harness for continuity/signal
5. Confirmed spark on each coil
6. Tested Compression - Values Ranged from 120-140 and came up 5-10psi higher when I added some oil.
7. Cleaned MAF and Throttle Body
8. Bench tested Evap purge valve for vacuum and operation
9. Smoke tested the evap system - I found a bad leak on the EGR valve and sealed it but it didnt help.
10. Sealed some cracks in the intake resonator - didnt help.
11. Tested the battery at Napa and they said it was good (12v sitting charge, 15v running charge)
12. Replaced downstream O2 sensor from initial fault reading
13. Checked the Coolant for exhaust gases
14. no coolant in oil or smoke of any type

It had bit of a gas smell for a while before the misfire started so there could be a leak that I didn't find. The compression seems a bit low and when I rechecked yesterday the values were lower across the board from about 115-130. Its possible that the block had cooled a bit though since I live at 7000ft in Colorado and it was snowing. Its been difficult to really pinpoint the problem since there are so many engine faults. I included the current faults in the attached excel file.

If anyone has any ideas of something I've missed or should recheck I would greatly appreciate the help. I'm thinking that my next move could be any of the following expensive options. Replace the other 3 O2 sensors, replace the injectors, replace the coil packs, start replacing sensors(oil temp, coolant temp etc). Replace Battery.

Thanks for the help.

 

I know this was posted some months ago but after looking through your Excel file, I couldn't help thinking that this looks like a power or grounding problem, you have so many faults that are not related to misfiring. I just got a P0304 (cylinder 4 misfire) and it looks like it is the ignition coil pack so new one will be here Friday, but you have so many issues that it is likely something common to the electrical system or maybe CANBUS communications. Hopefully you've discovered the fault?