AZ Power & Sound

iTrader: (2)

Ok, the car is a 01 SS M6, G5X2, Shaner S3, true duals, headers,misc bolt ons, stock fuel and custom tuning by LG... I origionally had the 85mm MAF on there as well, but I just put the stocker back on to see if it helped. Anyways cat has a BAD detonation problem at low rpms, and also TERRIBLE at 3rd gear higher rpms, I mean like consistent off the wall detonation. When I spray it literally almost slows the car down from so much detonation. On Autotap the car has LTrims pinned at 25 and they wont come off unless I let off the throttle, then they drop on decel. I stuck the car on a wideband and the a/f was a consistent 17-18:1 below 3000 rpm, then above went to 10:1. With a MAF Translator at 20% more base and 14% less WOT the best I could get was 16:1 a/f at low RPMs, then flattened out to a 12.5:1 high rpm. I checked fuel pressure and it is at a consistent 61 PSI (adjustable regulator) and doesnt move when I go to WOT. Ive tried a stock MAF and the 85mm so that isnt it. the car is in AZ where its about 110 degrees out usually and the best fuel we have here is 91 octane. Car never sees over 195 degrees and has not had a pinging problem until the cam and tuning went in, but at the same time I also did the 85mm MAF and Shaner S3.

Can anyone suggest what the problem might be? In addition (might be the mechanics fault, might not) but there is a spare vacuum line that he just plugged. It came off the "Y" from the back on the manifold and it is one of the two tiny lines. I wasnt sure if maybe that went to a regulator or some other part?

JWRENCH

Sounds Like who ever tried to tune this thing was smoking crack! I'd say the fuel supply is good if it's getting to 10:1 up high. Just try to go back and have it tuned right. And for god's sake don't spray it or you'll burn the pistons out of it in a hurry.