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ok, I tuned my '02 t/a with free m air mod, lid, full td exhaust, and ported maf w/screen last year and everything was about perfect. Recently though, as the weather has warmed up, i have started seeing a LOT of knock in the lower rpm range. Tuned last year in much warmer weather than what it's been so far this year. Checked plugs and wires and there are all good. Using tr55's gapped at .045. I am just at a loss on what to look for. WOT is clear of any knock as well.
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The only time I have seen that is when I was slowing way down, in third or fourth gear (mines a 6-speed LS1) and started accelerating again. Really loaded the engine but with the torque it has started pulling up to speed right away. Was surpriseed to see any knock and like you, didn't have any at WOT. I think your trims look good and don't show anything unusual going on there. Exhaust vibration/rattle??
Nothing noticeable. It seem like it only happens when in a steady state at lower rpms. I am also having a low voltage issue when it gets warm out. Solid voltage when cold and gradually drops down just below 13 as everything warms up. Not sure if that's effect anything like this though. Was planning on checking the exhaust this weekend, though. Just to be sure. Could a small exhaust leak be a culprit?
Decel used to be the only place I would see any knock, but it was very little if any. And when I get the knock now it can be as high as 15*
And by fine for the plugs, I mean that they showing signs of running a lil hot but still within limits of being ok. Insulator is white with a very, very slight shade of pink on a few plugs. Could I possibly just need a cooler plug? Is it common to need a cooler plug than I have for these mods?
It looks like most times KR shows up, the actual timing itself is in the low 20's. I have seen AFR get shifted around with timing. IE more timing is some times leaner and some times richer, it depends on quite a few things (RPM, too much/not enough timing, etc.).
What I am getting at, since it is low RPM, low timing prior to KR, could you actually be loading the cyl up a bit for that brief second causing KR? With out a wideband to look at, it will be hard to tell.
I believe STFT cycle themselves, reseting and re-establishing a base line. Could the STFT cycling be causing a slight load up while timing is low, causing KR?
Just something to ponder, not saying that is the case.
As far as your voltage issues, I saw the same thing with mine. Had the alternator checked at Autozone and Advance and both said charging system was OK. Then one day I noticed it wasn't getting above 13 volts anymore. Decided to put in a new alternator and problem went away. Had original tested and was found bad. Rebulit it to have a spare on hand. After talking with the repair shop, they said some GM car's alternators are controlled by the PCM (like ours) and will only call for a charge when needed so it will not always show a 14volt charge like some cars.
Hmm, definitely something to think about. I'm gonna take a look at my o2 readings up to right before the knock occurs. Maybe that'll shed some light. I was playing around with the idea of just starting back from scratch with some fresh SD VE tuning. Wish I had a wideband. All available funds going to the need a tranny rebuild/clutch fund.Quote:
Originally Posted by Super73
I had it tested off the car last year and it was good. I don't recall if it acted this way last year but I believe it did. May need to take it off and have it tested again.Quote:
Originally Posted by tpcaz
I have this same issue as well. When I roll into the throttle in the low rpm range, say 1500-2000 rpm, when in higher gears, I get audible knock and it goes away above ~2200 rpms. It only happens when I go above around 30-40% throttle at those low rpms.
It's a little troubling when you hear it, and then see the log that it was a consistent 4-6 degrees of knock.
Any ideas?
Checking in to see if you guys nailed it down.