bigblue95z

So I've got a knock during acceleration when I'm at about 30% throttle. It happens 2-4 times a second (linear with engine rpm) and is primarily audible from 2.5k-4.5k rpm. It sounds like it is coming from the valvetrain, or somewhere up top but I could be wrong. I've had it at the stealership 2x now. First (at 1000 miles) they said it was the trans being worn in an will fade. So now with 17000 they decide to replace the trans but the noise is still unchanged. I am at a loss and obviously so is the dealer and I want to finally get this issue resolved so I can start modding with a healthy v8. Has anyone heard of a similar issue so we can get some insight on how to correct it?

Thanks.

ski

Try higher octane gas. If it goes away, then pinging is the cause.
If you're already using 93 octane, then try different brands of gas.
If you've already tried these suggestions w/o success, then try a can of Seafoam in the tank.

GrayGhost01GT

Higher Octane gas! My 10 GT did it using that cheap crappy Murphy Oil brand of gas that Wal-Mart and Sam's club sells, when I was on a road trip. They are cheaper than everyone else for a reason! I went to Exxon and still used 87 Octane and it ran fine! I noticed when I mashed the accelerator and climbed to 5k on the tach is sounded like a coffee can with marbles rattling in it! It's probably the computer pulling the timing.

2cokeman

You definatly need higher octane, preferably with no ethanaol

bigblue95z

I see how you could think it's spark knock, but 4 techs have driven the car and all have said no way it's spark knock. It's too deep and infrequend they say. I'm just really getting frustrated. A data log should show if it is infact spark knock, correct? I've got an sct on order, does that have the capability to log knock sensor readings? Thanks for the reply guys! Keep em comming! I want to tear into this but don't want to until I know I'm starting with a healthy powerplant.

bigblue95z

So just to be sure it wasn't spark knock, I ran down to e, filled up with 93 octane, have driven 100 miles on that tank and still have the noise. This is getting very frustrating. Just want it gone.

HypromanGT

Yes, you will be able to data log with the SCT, and you should be able to look at the knock sensors and timing advance to see whats going on.

I am wondering if it's not knocking but a different sound. A lot of folks with the "separator plate buzz" commented that they thought it sounded like pinging, but that it happened at part throttle as well, and it only happened in certain RPM ranges. I know I have an undiagnosed sound that almost sounds like bad knock, but I know it's not. These cars tend to make some interesting noises; some are harder than others to figure out.

Anyway, with the SCT data logging you should be able to confirm or rule out spark knock once and for all.