Strange Knock Issue. Step inside so I can pick your brain... - GN and T-Type Performance Enthusiasts (GNTTYPE) Forums

PhillyTurboSix · #1 05-11-2010, 10:51 PM

Well I've got about 400 plus miles on the new rebuild and I've got this strange knock issue that just showed up. I have the turbo tweak fast update chip in the car. What will happen is I'm driving down the road any speed and sometimes when I give it a little gas just to maintain speed I'll see some quick knock show up on the scanmaster. It will be something like .02 - 1.9 - .07 - 2.9 - 1.2 - .06. and numbers like that. It will come really quick and seems to go away as quick as it shows up.

When it's doing it and the car happens to be near a shift on the shift I'll see it jump to 2.9 real quick on the shift. Car feels and runs fine. I don't hear any detonation or pinging at all.

The knock sensor is brand new and torqued properly. I also found the last NOS ESC module in the country on a GM allocator and replaced that. After replacing the ESC it's still the same just not as bad. It's not all the time. I could drive the car for miles and miles and nothing. Comes out of no where goes nuts and goes away totally randomly in any conditions.

I was at a show and got caught in a major down pour but the car sat there, got wet, I dried it off, waited for the roads to dry, and went home. So that's why I thought maybe the ESC module took a crap when that happened because it seemed to appear after that. I cleaned the connector on the ESC and knock sensor.

All grounds on the back of the head have been redone when I did the engine and made sure they were all cleaned up and I re-crimped some of them. So what else would be the next trouble shooting step? I have about a dozen ECM's I thought about replacing that.

PaCemkr86 · #2 05-11-2010, 11:41 PM

what does it do under WOT ?

also, does it show any knock if you slowly roll into it in 3rd gear and floor it?

PhillyTurboSix · #3 05-11-2010, 11:57 PM

Well because I'm breaking it in still I have not gone WOT with it. Only maybe half pedal tops. Trying to give it a easy break in. I put about 12 psi thru it so far. The knock is all without any boost at all when it comes and goes. I was going to change the oil over the weekend and maybe try some more boost thru it after that. Right now it has Comp Cams break in oil 10w30 with a little ZDDP.

PaCemkr86 · #4 05-12-2010, 12:03 AM

i wouldnt even worry about it till you start making some boost under WOT.

turbodave38 · #5 05-12-2010, 06:47 AM

Certainly sounds like false knock. Probably caused by something clattering against something else. Downpipe close to touching something?? Look around for things touching or things loose.

kenmosher · #6 05-12-2010, 11:22 AM

I'm with Dave ... also, valve train noise ... if you have roller rockers, I'd check for preload and such.

PhillyTurboSix · #7 05-12-2010, 06:21 PM

No roller rockers. The entire engine bay is stock along with the downpipe so I don't think that's hitting. It can be when I'm just going along at 25 mph nice and smooth and it will just come out of no where. I'm thinking false only because there is no rhyme or reason with it and it comes and go at anytime. Just strange.

PhillyTurboSix · #8 05-13-2010, 02:20 PM

Had it out today put about 25 miles on it highway, in traffic, and rolling along 45-55 range and it only did the funky knock thing one time in one instance. I was taking off and it started just before the 1-2 and during the 1-2 and that was it. I love this fast update on the TT chip. I get the info damn near real time on the Scanmaster for sure. The entire rest of the drive nothing.

I think this car has a Walboro pump in it and do you think possibly the fuel is dipping at these weird knock times? It's several years old the pump and it could be around the time the bad batch were around. I have a Casper's fuel gauge with the hose so you can put it under the wiper maybe I'll throw that on just to see if the fuel pressure is doing funky stuff..

Nothing like trouble shooting something so intermittent! Make ya nuts!

And just for Phil I put 15psi thru it one time

and only saw some shift knock.

Almost seems like the knock sensor is way to sensitive at times. I dunno I'll keep pulling hair out

PaCemkr86 · #9 05-13-2010, 06:30 PM

do you have any powerlogger files for us to look threw? In the past on my cars, if it wasnt showing any knock under boost i didnt worry about it

PhillyTurboSix · #10 05-13-2010, 08:35 PM

Well that's the next step. If I can't hunt down something causing false knock. I have a number of spare ECM's so I can always pop the power logger adapter on a ECM and do some recording. I was thinking about doing it just to see where the fuel is. I was under the car checking the exhaust tonight and it all seems to be tight. Looks like the crossover might have touched the frame on the pass side there where it's close but it don't look like it's been hitting on a constant basis.