2003 Z06 Spark Knock problem

[Irv]

Since we've moved to Oregon from SoCal, on hot days with the A/C running, my '03 Z06 sometimes exhibits some significant spark knock under mid-rpm acceleration. This isn't the "light pinging" stuff, this sounds like marbles in the bores. That can't be good for valves and piston tops. Somewhat surprising since premium is 92 octane here, versus 91 in CA. Turning off the A/C helps. No discernable knocking when it's cool.

I searched the internet and threads on this and various boards and found there's an alternate ECM calibration (part number 9358673) to reduce spark knock. I made an appointment to have my nearest dealer install it, and when I got there they recommended against the update for two reasons. First, they said they applied one of these anti-knock calibrations to another vette (unspecified year and model) and the owner noticed a power deficit all of the time, though the knocking went away. Second, the owner wanted to undo the calibration and found you can't undo - the ECM has to be sent back to GM for a refit.

Another dealer, the biggest Corvette dealer in Portland (though nothing to shout about on a national scale) says they've heard no complaints about recalibrations, but couldn't say if they've ever done this particular one. So now I'm confused about what to do.

Has anyone on this board with an '02-'04 Z06 has the recalibration for spark knock done? If so, what's your experience with it? Can dyno-tuning shops help cure this knocking, for a custom solution?

 

[bobby1]

Throw a can of 104 octane booster in.. Bet knock goes away--dont let dealers play with anything!!

 

[hzl6cm]

You should not have spark knock with the car. I have an '04 Z06 and have never had spark knock here in Kansas City even in 100 degree plus weather and running 91 octane gasoline. I have also run 89 octane gasohol (10% ethanol) on ocasion without any knocking. Even when my wife filled the tank with regular (87 octane) I didn't get any knock. I'm wondering if you have a bad knock sensor.

 

[DRTH VTR]

I'm wondering if you have a bad knock sensor.

That was my thought, too.

 

[Big Red Machine 1]

Another option:

I just had my 04' Z06 tuned here in Vancover, Wa. & the tuner said that the computer has another set of backup tuning tables that it will automatically switch over to when it senses knock, like when you put lower octane in. Now that table can be removed by a tuner, but he recommended not to as you have no protection with low octane, or bad fuel. Did someone, before you owned the car, have this backup table removed?

 

[RHP]

I agree with HZl6cM-

You should not have knock. Are You throwing (showing) any codes?

Possibly a knock sensor. Have you posted on any other forums?

 

[TODD L GRIFFITH]

I was thinking the change in elevation could be a factor. Do you have an aftermarket exhaust? Those knock sensors are so sensitive that maybe it could be picking up noise and the interpretation is knock. Without any codes, I'd think that it could be something else.

 

[ErnieN85]

I can't say about you but I had the problem last week after a fillup. I'm pretty sure that the high test pump had been filled with regular.
As soon as I got another tankful the problem mysteriously went away!
I'm going to complain to BP as soon as I get my bill this month!

 

[MsSchroder]

I searched the internet and threads on this and various boards and found there's an alternate ECM calibration (part number 9358673) to reduce spark knock. I made an appointment to have my nearest dealer install it, and when I got there they recommended against the update for two reasons. First, they said they applied one of these anti-knock calibrations to another vette (unspecified year and model) and the owner noticed a power deficit all of the time, though the knocking went away. Second, the owner wanted to undo the calibration and found you can't undo - the ECM has to be sent back to GM for a refit.

Another dealer, the biggest Corvette dealer in Portland (though nothing to shout about on a national scale) says they've heard no complaints about recalibrations, but couldn't say if they've ever done this particular one. So now I'm confused about what to do.

Has anyone on this board with an '02-'04 Z06 has the recalibration for spark knock done? If so, what's your experience with it? Can dyno-tuning shops help cure this knocking, for a custom solution?

There was a post here in which a member inadvertently got the spark knock recalibration when his PCM was reflashed for something else. He was not pleased with the results- but he didn't have knock to start with.