how do i stop my 02 z28 automatic from getting spark knock, i run nothing but 93 octane, i installed a 160 thermostat, and seafoamed it twice already, not sure what else i can do, it only does it at high rpms

 

How many miles on the engine? Do you have any mods and has it been tuned? You could have a problem with an injector running lean. GM makes this really good injector cleaner that I'm pretty sure you can get from the Dealer. Maybe try a bottle of that?

Also, you haven't added any "stop leak" to the cooling system have you? You could have an issue with the cylinder heads being too hot if that stuff plugged up the chambers or something.

Or, you could have carbon build up on the valves but you already seafoamed so hopefully that would fix it if that was the case.

 

Subscribed. I'd like to know too since I seem to get what I suspect is knock after a wot run for a second or two, then it goes away.

 

Some good suggestions in here.

How much knock are we talking about? Is it audiable, or just knock retard you're seeing on a scanner? If it's not audiable and is a small amount, it might just be false knock from something banging somewhere (exhaust, etc.).

If you can hear it but haven't scanned the PCM yet, then I'd plug in a scanner and do some logging. Look at coolant temps when the knock is happening, get a reading on just how much knock retard you're seeing (and what the max timing advance is when this happens), and look at some O2 sensors values (see how rich/lean the exhaust is showing). Also, first order of business would be to scan for codes.

Could be a dirty/bad MAF, poor injector spray, poor fuel pressure, hot spots in the cylinder heads, bad tuning (if you have a tune), spark plug and/or ignition problem.

 

agreed, i was having the same exact problem for a while on my car and it turned out the maf was getting sluggish on me, it wasnt throwing any codes and i tried cleaning it and it did nothing.. the best thing you could do is what someone else on here told me when i was having the same problem. go to the parts store and buy a maf, put it in and take it for a ride if the problem is gone all is well. if not take the maf back and tell them you didnt realize you have a custom intake setup and it doesnt fit. then return it. or you could just have someone log it on a laptop for you but i didnt know anyone with the know how or have the money to spend on someone who does. hope this helps. also dont run a ported maf or aftermarket go with acdelco. you will only have problems if you do.

 

nterested in this too. Was getting knock just before redline on the dyno. Was asked if I let the gas sit all winter, no I just filled up with 93. I got it from QT, I asked them about it and they did not seem surprised and offered to refund repair prices. Next time I will try a different brand of 93 and we will see what happens.