RB25 Misfire trouble

[RBZ32]

I'm running out of ideas. This started on a drive home from Seattle. On the highway the car suddenly was way down on power and I could tell there was a misfire from the sound. Then it went away after 5 mins, but then a few miles later it started again and hasn't gone away. I changed the spark plugs and used a smaller gap for them and the problem stopped for 3 days. Then it started again. The misfire happens at all RPM's, cold and warm engine temp. I checked the coil packs and found that #6 is the problem. Cleaned all the coilpacks, didn't help. I changed the coil packs around and #6 still misfired with a different pack on it. The pack from #6 that I moved to #1 worked fine there, and the pack from #1 that was working, now wasn't on #6. I then checked the spark plugs again and found they were ok. Changed the #6 plug with a new one with proper gap and still misfires.

Anyone have any ideas what else to check or could be causing this?

[MoogLe]

bad injector maybe?

[RBZ32]

Just checked the injectors and they are all working as well.

[Joe]

move injector number 6 to another cylinder

if that doesnt fix it you need to do a leakdown test.

[RBZ32]

Moved the injector from #6 and still had the same result. A leak down test is the next thing on my list to do.
Modified by RBZ32 at 5:58 PM 9/20/2009

[Joe]

also verify voltage for injector and spark from the ecu/at the plugs for cyl #6

[Cjmartz2k]

if that doesnt fix it you need to do a leakdown test.

Hopefully you won't get bad news from that, but I wouldn't have my hopes set to high. What does the plug look like from the cylinder that keeps doing the missing?

[RBZ32]

The plug out of #6 is black and wet.

I pulled the radiator cap and the fluid is still a health green. The oil off the dipstick also looks health, but the once the leakdown test is done, I will know more.
Modified by RBZ32 at 6:30 PM 9/20/2009

[Cjmartz2k]

Strange. And you said it does it at light throttle and idle, not just WOT? Maybe intermittent wiring problem, bad ground, or bad ignitor. Just guessing at stuff.

[rb25drag]

You might have a burnt valve, DO a leak down test as well as a compression test.

[RBZ32]

This misfire is at all throttle % including idle and w/ and w/o boost. As Joe also said, I'm going to run a voltage test at the ECU as well. The more things I rule out and check, the closer to a solution I'll get.

[Cjmartz2k]

Sounds like sound trouble shooting technique to me

[RBZ32]

The problem turned out to be bad wiring and a bad ECU tune. Thank you for all of your inputs and ideas to help me solve this.