MISFIRE @ HIGH RPM 1 CYL.

[Pateswap2]

So, I have an 2006 TBSS I bought in August Stock. Since then I have all at one time had it out of commission to do.

VMS Coils, MSD Wires, NGK TR5 Plugs, Fire Boots.
Billet Oil Catch Can.
Polished TB.
K&N CAI.
IAT Breakout Harness (PCM)
SPL Underdrive Pulley
LS1 Fans PCM 3 Relay Kit. (PCM)
Tune and Fan Patch. (PCM)
SLP 160 Thermostat.
AeroForce Gauge
OIL Pick-Up Tube. ( PCM).

I did all this amongst many other things which did not involve the powertrain all at one time. Since 1St Start up. it seems to run great.But At high RPMs. in 2nd Gear at 5K-6K RPM. I noticed a BOG in power. It took a few times for me to make sure I wasn't crazy, then after 4-5 times of repeatedly attempting this I got a Flashing CEL. so I back off and scanned the codes. got PO300. Random Misfire. The light never stayed on. only flashed a few times and goes away.

I'm being very specific so please bare with me and read through. After checking the obvious plugs, wires, and boots. etc. I hooked my scan tool up to watch misfires. I saw #8 MISFIRE going off the charts in this high RPM range. So i Checked everything. no luck. Swapped. Plug to 6 no luck, swapped coil to 6, no luck. swapped wire to 6 no luck. Meaning my misfire did not jump. SO then. I started wondering. How and Why. I never had this issue before. I have narrowed it down to being a fuel/Ignition issue. As when its COLD. its not so obvious/ when its Warm-HOT it gets worse. So I have put back the Platinum plug and coil and wire just to see and still no luck. I have changed Octane up and down. no luck. Still misfire on #8 @5-6K RPM. I have Checked Coil Driver wires and harness, also Injector driver harness no Issue.

Recently I have gutted the cats seeing high CAT temps and thinking to much back pressure when warm. and replaced both upstream o2s unfortunately no luck. (Sounds killer on stock Exhaust thou). Also playing with the RPMs at this RPM range watching the Scan tool. It only does the misfire @ WOT. I can give 1/2 throttle threw same rpm range and have no issue. even 3/4 throttle with barely any misfire occurring. Free Rev in Neutral shows nothings. I have ordered TR6 plugs and one single PCM Wire for #8. to eliminate any Spark Scatter under serious load. and a colder plug.

I would hate to say a Bad Tune. but I will be next swapping injectors, compression test, leak down, Spring check, as I don't want to point fingers but ive now got a lot of time and money tied up into this beast and I cant even have fun in it.
Looking for some info and making sure I'm on the right track. Thanks.

[Gzero]

Sounds like the tune. Swapped everything already.

[Pateswap2]

Yea that's pretty much what I was thinking, I cant see anything else Failing all of the sudden.

[Gzero]

Have you talked to PCMofNC about your tune? They've been really helpful with mine.

[Pateswap2]

I'm waiting for an Response via Email.

[Pateswap2]

SO I finally got my ECM to PCM of NC they stated tune looked ok. but it could still be a bad ECM internal issue. which I never had an issue before. So I would have to buy a new one and let them flash it over....

[Gzero]

That's crappy. What is their price for a new ECM? You could always use a second ECM to correct stall converter/speedo lag in the future.

[Pateswap2]

Yea it would close to $300.00 So I will check a few more things in the mean time and see what I can come up with before I go that route. PCM will help me out they have been real understanding with whats going on.

[pwrplnt1]

I'd swap all the factory coils back in and see how it does.

Sent from my E6810 using Tapatalk