I have talked about this phenomenen with Ken before, but I need to bring it back up.
I have a Snap-On Scanner....I know, I know it's not a turbo specific, (like turbolink!). It gives me the info I need for now. AT IDLE...I am showing knock. The only thing that is touching the frame of the car is the motor mounts. I double checked to see if the down pipe was rubbing the header, but it is not. I put it in diagnostic mode and it showed no knock, that is until I tap on the block near the sensor. When I go back into "Road Test" the little LED designated for knock is lit. There are no ESC counts, and no reatard at WOT, But that damn LED says KNOCK! I do not hear it, no pinging, no nothing. I am starting to suspect the sensor, but the test showed that it works. Is it possible that an e-prom is to blame? Could the chip I run, (thrasher in prelim. test.)be the culprit. I have three other chips that I am going to try.
I also can not achieve closed loop after 10-15 minutes of warm up time. I go through O2 sensors once every couple of months - due to my inexperience in tuning - but I am learning! I do not get codes for the O2 sensor with the thrasher, but I do with the GM emissions chip, ZIdustries, and Minimag. I do not claim to know why the O2 sensor hates me, but I must have crossed it the wrong way. I know that you can not give me definitive answers on this since every car is slightly different, but anything will help. I will leave you with a list of changes done to the car to give you some insight in diagnoses. As always, this site and everyone involved have been a great help to me.
87' GN
K&N Cone (12")
Solid MAF pipe
237 regulator
W 340 pump (not hot wired-plug and play)
RJC Dist. Plate
Kenne Bell 3" down pipe straight out the back
TPS/TEC
Stock Turbo / intercooler (10-12 psi daily driver)
Stock injectors
Thrasher 92
Minimag
GM updated prom
ZIndustries Off-Road (91' or 92' ?) it's old, but the car really likes it.
Not sure, but there may be a cam
not sure, but there might be some v-spring work
I just want to get the car right before I even consider beating on it. It has never been run legally or illegaly. No one ever says "you're too carefull." in a bad way.
In case anyone was wondering, I suspect the Snap-On Scan Tool as well does not like me.
I have heard of others with the same problem with the snap-on. I think the scanner is your problem. Buy (or beg, plead, and borrow) something else. There are some free PC based (non TR specific of course) scanners on the web if you are even slightly handy with a soldering iron. You might try a search for "snap-on" and see if anything pops up.
I put the Minimag back in. (who makes this chip?)
Still showing knock with zero ECM counts. If I put the scanner in Field Service Mode, I show no Knock and zero ECM counts.( this is about where I passed out from confusion.)
I did, on the other hand manage to achieve closed loop thus making it possible for me to set min/air rate and IAC. I removed the knock sensor, added some teflon tape and torqued it to 14#. Same readings. (Ken) I remember you writing to me and telling me that the Scan tool I use reads Knock differently than the Turbolink. Are these false readings? Also the Thrasher I use is suspect of the open loop. I know that you can remove the O2 sensor all together with that chip. Later this evening I will see what the O2 mv are in 3rd gear at WOT. Looking for 750-800mv.
It's looking more and more like an issue with your Snap On scanner reading the data incorrectly.
The Thrasher is open loop at idle, by design, so I'm not surprised you see that.
Field Service is a special mode, so I wouldn't use that for setting things.
It is the Scanner. I went out and ran some tests on the car last night.
I had 3 degrees of knock @ 3225 rpm - 02=863
I had 2 degrees of knock @ 4050 rpm - 02=844
I feel as if everything is working fine, the snap-on was trying to give me an ulcer. I was running 14-15 psi and the car seems to still be rich
(800+ mv). Can I safely turn the boost up to compensate? Maybe 16-17 psi.? Through 8 seconds of tear-ass, the mv range was steady in the upper 800s'. Is 5 degrees of knock what I should expect if I do turn it up? It was not field service mode as I stated. I made a mistake. It was the troubleshooter mode. As far as what I have read, the car can't be driven in any mode other than Road test. Thanks for your help guys. I shall continue my journey with a little better understanding.
I don't think turning up the boost is a good idea. Three degees of knock is about as much as you would want. If it is rich "across the board" you can try turning down the fuel pressure (of course you need a adjustible regulator). The o2's at wot are probably going to show a little rich due to AE (acceleration enrichment) anyway. Most shoot for 750 to 800 anyway, so you may be OK. The best why to check for fuel mixture is too look at the BLM's at 128, you will need turbo-link or something similar for that.
How did you do your "new" testing?
I am FAR from REALLY knowing what I talking about, but I do KNOW that a good scan tool IS a MUST.
As far as "new" testing goes, it was the same thing I did last night. I did turn up the boost another 1-2 psi. and still getting a rich reading. I plan on going to visit Dennis Kirban this week while I am in New England. I will scoop up an adjustable regulator.
There's a road a little ways from my house that is pretty much abandoned. I can only get the car to 80 mph before I need to start thinking about my immediate future. I launch the car at or around 8-10 psi. and hope for the best. I have a mountain of spreadsheets (w/scantool info)in my office that I am trying to decypher. Of course better fuel would probably help. "new" testing just means "new" to me.