an-i-no

iTrader: (1)

Hello there ppls. I recently purchased a 1999 Camaro Z28 in (seemingly) great condition with just 77k on it, but I'm having an issue with what I believe is spark knock/detonation/pre-ignition. Its a very faint metallic clank or tick or rattle at part-throttle and right after gear shifts when the motor is hot. When I go WOT I don't think it's there (wind noise drowns it out maybe?).

When I'm driving first thing in the morning I have no issues. I can recreate it at will and I've had the car since November and put around 3k miles on it and I just recently started to have this problem. No codes come up at all.

So I did my homework, and bought a scanner to see what the computer tells me. When the coolant temp gets to 215+ (partially due to heat soaking I guess?) and the outside temp gets to 70+ I get the noise. I can see anywhere between 2 and 8 degrees of knock retard (in one really bad case it shot up to 10) so again, I'm pretty sure it's spark knock.

I've seafoamed the car twice, and got no smoke at all either time. I put a full can of seafoam in a full tank of gas and it seemed to help greatly. As soon as I changed the fuel filter and got another tank the problem returned. I usually use generic 93 gas (from places like Stripes or Valero) but I went through 1 and a half tanks of Shell 93 and a half tank of Chevron and that didn't help either.

At this point I've done all the little tricks I read about and it hasn't gone away. I'm going out to triple check for vacuum leaks but aside from that I'm at a loss. Should I be look at the cooling system or pulling spark plugs? New thermostat maybe?

Thanks in advance.

theblackta00

My 2000 trans am had a simaliar issue. I read on here to try and clean your MAF sensor to see if that helps. The wires inside there can get a fine coating of dust and gunk on them and will not read the right air flow. Witch can make your engine run lean