Ok heres the problem and I am about to smash the damn thing with a hammer. I need to go get my Emission test done again and the damn knock sensor takes a crap 2 days before I am about to go. So I buy a new one from Gm and I put it in. I get the car warmed up and take it out for a drive. The car runs ok but something is wrong. So I plug my Scanner in and watch the timing table and knock count. If the car is at idle and I give the throttle a quick hit, the car will back fire every now and then. I then noticed that the car gets a knock count every time I do this and it drops the timing down to around 16 to 17 degrees and then it climbs back up. If I slowly give it gas the timing is normal ranging from 36 to 40 degrees. When the car is in open loop, It runs like a raped ape. But when it goes into closed loop, it seems to loose power. Everything on the motor is new, I mean everything!!! All gm sensors and new plugs and wires. The car was running ok before but I did have the closed loop/open loop power difference before the knock sensor going out. I know this is a case of false knock but I cant find out where its coming from. I tried racing fuel in it but it didnt help the knock scenario. Can I just tune the knock retard out?? The car does have a Dyno tune on it done by Speed Inc. Any ideas would be greatly appreciated as I need to get this damn Thing running right soon so I can pass emissions. THanks

 

Yes, just zero out the MAP KR table and retard vs temp (burst) knock table.

 

Why would this prevent you from testing for emissions? They don't stomp on the throttle during testing. If you're convinced that it's false knock, you can either go the LT4 knock module route or desensitize/defeat the knock sensor. The risk is if it is real knock, you can do engine damage (can you say blown head gaskets).

 

It's very doubtful that he is getting real knock especially at part throttle. If it's the engine knocking (rod/bearing), no retarded timing will help.

KR can occur both at WOT and part throttle. Since the PCM is retarding timing causing his car to run poorly, he will most likely fail if he took it to emission testing like that, that's why he's looking for a solution.

 

Thanks for the info Ion. I was thinking of doing that but wasnt sure. I already have the LT4 knock module in this car OBE1. I do know it is truly false knock. The motor is not knocking at all and if it was real spark knock, It wouldnt do it just tapping the throttle in park. I also tried some racing fuel to see if it would eliminate the knock sensor going off then I would have been convinced it was real spark knock. But it didnt help. So I am gonna have to just change the perimeters you mentioned Ion. Should I zero it out all the way or would you leave it in affect under wide open throttle? I guess I will run a datalog tomorrow and see when it happens the most.

 

Just leave it on for now at WOT. They won't go WOT during the test, so it doesn't matter. You can figure out what's wrong after the test and then put it back in.

Was your old KS rusty?

 

Thats the funny thing, I had the original one go out about 2 years ago and I needed one like right now so I took it out of my other Trans am since it was apart. It was in great shape and it worked great but went out today. When I took it out, it had no rust on it and still looked fairly new considering it was the original from the other Trans am. Is it common for these things to go out? Hows the 6 speed doin for you? I see it was the Flywheel bein warped. Hope it is goin good for ya now.

 

I wouldn't say it's common for them to go out. In fact, it's more common for the computer to go out with a KS circuit code. (but the problem is really the computer)

Did you try another one? Is it a regular parts store one? If so, I would try GM.

The 6 speed swap worked great. I resurfaced the steel flywheel and shimmed it and it's perfect now. The clutch pedal is still lower, but I don't mind that much. I might take the cylinder later on to a local machine shop and have them make it adjustable for me, but for now it works fine.

I did have a very bad rattle when stopped and very low speed and it turned out the crossbrace was pushing up the y-pipe a bit and it was hitting on the torque arm. I took off the crossbrace and it's fine now.
The only problem I have now is vibration at 80+ MPH from the tranny. I had the exact same thing on my old '95. (this car had zero vibration with the A4)
It has an LS1 driveshaft, so that's not it. I might try an LS1 tranny mount to see if that makes it better.
Thanks for the help.

 

The knock sensor I put in it is a new Gm one now. THe last 2 had some miles on them so it could of been just the case of an old sensor gone bad. I put the new one in and cleared the code and took it for a drive and it never set the code again. I tried clearing the code with the old knock sensor still in and it come back on in a matter of seconds.
On the vibration, Does it do it only at that mile per hour or does it happen at a certain RPM? I had this problem with my 95 when I installed a Ram clutch (piece of crap by the way) I changed the clutch after a year to a Centerforce and the vibration went away. Who rebuilt your tranny anyways? I appreciate the help with the knock problem. I think it might be the damn headers I am using. They are Mid length's and are the BBk's. I should of just went with long tubes but was afraid of passing emissions with the car. O well what can you do. Its the wifes ride so I dont want to get to stupid with it. I reserve all the stupid crazy money objects for my Trans am. LOL

 

I also was reading what you wrote again about the computer usually going out. Think I should reprogram another computer I have here and put it in and see what it does?

 

The rattling I was telling you about with the exhaust and torque arm, that was also causing a bunch of KR for me. Enough to kill the car. (pulled 7 degrees of timing or so at idle and it became unstable)
So it is possible that you are getting KR from some rattling too.

It wouldn't hurt to try a different computer, but I'm almost positive you will get the same results.

You can also just try another sensor. I used a Napa one in the past and it worked fine.


As for the tranny, it was rebuilt and dyno tested by a shop in Oklahoma. I'm very happy with it in all aspects. (shifts great, makes no noise even with Spec III, etc) It only vibrates at 80+ MPH just like my old 95. (the 95 also had a polyurethane tranny mount and ls1 driveshaft)

 

What kind of scanner do you need to see that you have false knock? Is false knock then programmed into the PCM to give you bad timing? Ion, would you be able to "retime" it if the false knock was making it run poorly?

 

You can use any scanner to see when the knock sensor is picking up knock. Telling if its false or true is the hard thing. I used a matco scanner and drove the car around and recorded the counts and seent he timing being pulled. You can also do this with a datamaster.

 

Can you use the matco scanner to pull an ABS code?

 

Ion, I also installed the LS1 Trans mount in my car. The nice thing about it is it is still soft enough to eliminate some vibration but is made with a lock built into it so it wont tear apart.