Bill Dearborn

Speaking of Rabbits I had two of them the next morning. Ambient temps were in the upper 40s so tires and pavement were cold. The misfire didn't occur during this run but we didn't set any new lap times. The other Z06 is owned by a forum member but I can't think of his name right now.


Bill

23/C8Z

congrats Bill! awesome job.

PS. did you ever replace the spark plug since the last time you had this issue? still believe that's the most likely culprit. looking forward to any news about a fix for you.

360Lemans

Yep exactly what I was thinking. If it was as simple as plug, wire, or coil the Z would have been repaired by now! Why do you think the TECH keeps bleeding the intercooler coolant? Because GM knows what the problem is???

Bill sorry for your problems hope you get it fixed. I have to say this, when you get tired of power loss on the track you will eventually have to handle your high IAT temps with larger bricks or intercooler. I know, been dealing with this issue for almost two years now.

Pacembellum

Bill said it was 40 degrees out i really dont think it was IAT's.

cheapthrills

Nice work, curious have you had the suspension upgrade done? If so do believe it had value on the track as well?

360Lemans

No, He had no misfires during the first sessions (40s) but later in the day it was 60s when he stated the misfire started (see below from Bill 3rd thread).

Around 60s and above is when my power loss starts and then limp mode if I don't short shift and keep pushing the Z hard. Of course I have the A8 so it's probably more evident than what Bill is experiencing. So why did we have the same codes and my dealer also has bled the intercooler system several times just like Bills is what I can't figure out?

Bill Dearborn

Yes, I did have the upgrade done and it may be helping. However, I did find I still can't get all the way wide open when accelerating off the apex of Turn 1. If you watch the beginning of my fast lap you will see the back end kick out as I am trying to accelerate off the apex of T1. If I delayed going wide open a few more feet then it would stick. The graph of my speed data shows the kick out as a sudden spike in mph and if you listen carefully to the audio you can hear the engine rpms increase.

Bill

Bill Dearborn

The last two track events the misfire seems to be happening more often than last year and much more than the previous year. The first year I was driving the car it came and went even on the hottest afternoons or the coolest mornings. Last year it came and went during a hot afternoon session. This year after two events it seems to not happen on cool mornings but is still sort of inconsistent as far as ambient air temps go. When we got to the track on Saturday morning there was frost on the car windows and it took some time to get the frost off the windows. Going out on track during the first session was a little biting as the temps were in the low 40s. By the time the second session came around the car was misfiring quite badly and when I took my student out during the third session it was misfiring bad enough it could be felt by both of us in 2nd, 3rd and 4th when pulling off Oak Tree and going up the back straight. On Sunday morning the the ambient temp at the track was in the low 40s when we got there and when I went out for the first session it was in the high 40s. It didn't misfire during that session and it didn't misfire for about half of the second session. I even hit my personal best VIR top speed at the end of the back straight during the second session. However, it went downhill from there and the top speed started going down. The CEL cleared sometime during the second session and didn't come back as after riding with two more sessions with my student I decided I was too tired to do anything but the 3 hour drive home.

I talked to the mechanic when I dropped the car off and he said he agreed we had bled the intercooler enough times. I told him to keep the car as long as he needs to get it running correctly and to fix the PDR issue.

Bill

badhabit_wb

When I had the loss of power issue the only code I had was for a knock sensor. I added some coolant to intercooler and next track day all was well. Last week I pulled the fender liner and disconnected the tank and got more air out. Back to VIR south course next weekend to see how it does. The Mongoose Pro really helps a lot as far as seeing the codes etc.

383vett

I had no idea all that would be required. If they do get around to changing the ignition components and the problem still exists, I'll throw this out... valve springs on #8. I would have no explanation why only one cylinder would be affected, but a bad spring would possibly give you high rpm misfire which would become progressively worse. Not sure if the computer could pick up a mechanical issue though. Just a thought.

Mad Dog 24

Bill congrats on the PB and especially with a performance problem too Sure hope they get it figured out then you may be giving Sean a run for the fastest Z06 time at VIR! Jeff B. would be telling you to cage your car at those speeds as he does me now and then.

Looking forward to hearing what the final fix is. Years ago someone here had a similar issue and it was a loose O2 sensor wire getting hot bouncing around the exhaust, just a thought.

I still have a few weeks before our first time out this year.