Crazy Scanmaster knock readings?

[tlturbo]

I posted this on the Scan Tool board but since I hardly read those posts, I'm putting it here also.

I'm getting crazy knock readings on my scanmaster and I want to make sure it isn't something someone else has run across before I tear into looking for it.
I can be cruising along at a nice steady speed 25-30 or 65-70 for example and the scanmaster will show knock that jumps all over from 0 to .5 to 20 to 8 to 11 to 15, just all over and the O2's are in the 700-850 range. If I push the recall button there isn't anything there and I don't hear anything knocking.
How in the workd can you get knock just cruising along at a steady 30 MPH?
I've got a Max Effort 16 pos and 55's if that helps. Right now it's all set on default settings.

Any ideas?
Thanks - Terry

 

[scottyb]

You're cruising at a steady rate and you're getting knock and O2's upwards of 800? I'd first suspect a bad O2, then a sticky EGR, or both. Looks like a lean condition because the computer is leaning what it "thinks" is a rich condition, because of a bad O2 sensor. Your O2's should bounce all over the range at cruise (possibly < 100 to > 700).

Recall on the SM only works after WOT. WOT is when it "records" the critical values.

 

[tlturbo]

Steve's thumbwheel chip always runs in open loop and doesn't use the O2 sensor so I just look at it for a reference. And yes, the O2's do vary all over the place.
Also the EGR is totally removed and blocked off.

Thanks for the ideas though.

Terry

 

[scottyb]

OK then. Bad knock sensor? Something else tickling the sensor? Does the knock go away if you add octane?

 

[BADINBLACK6]

Terry, check the connection on the scanmaster if you have it plugged into the front of the aldl (mine is hard wired in the back) if it is loose it can give weird readings. My buddy had his stuck in the front and at idle it would show like 50* knock we put a new spade connector on it and it plugged in alot better and haven't had a problem since.HTH

 

[tlturbo]

Thanks guys,

I have SMC alky and the car will be showing knock just poking around and then I make a run at 18 psi and get NO knock on the run. Then I do it again and get 20.
So you might be right. I'll check all the connections and see if that helps.

Thanks again - Terry

 

[lrover2]

I have the same problem right now. You get knock at 1/4 gas also right? WOT things are good. CLEAN out your EGR passage. Mine is so blocked I was blowing boulders out of it. Take off your plenum and EGR and put compressed air through it. If you dont get air flow or very little this is most likely your problem. I have to do it again myself. I could only get minimal air flow through it until I locate a good roto rooter tool. Or you can get a chip that ignores the EGR. Hope this helps. I know what you are going through though. My knock has cleared up 50 % since I have done the first cleaning.

 

[gnfanatic]

I have the same exact problem NOW it doesnt go on! I only used the damn thing once to. I bought it used . I wonder hw much it costs to fix these rthings. I called ram chargers but Mike was noi there at the time.

Ralph

 

[6SENSE]

Ive had this happen before on different occasions (different years) and I believe I had different culprits. I swapped my ECM and cured the problem the first time this happened. Once I swapped the ESC module (dont forget about this, it is the link between your knock sensor and ECM). Also, I had and issue with lifter preload and had enough light tapping in the motor that even coming off the highway (when I let off the pedal) I would get false knock. I also had the cruising thing going on and upon acceleration. It was not an everytime thing, it would come and go. This instance was pretty recently.

 

[J Banning]

lrover2: Did you ever resolve your problem? I'm having the same type of problem with mine.

See here:
http://www.turbobuick.com/forums/showthread.php?s=&postid=555423#post555423

-Banning.

 

[tlturbo]

Nope - I haven't had a chance to play around and see if I can fix it. Been fighting bronchitis for a couple of weeks now.

Couple of notes. Heads don't have EGR passages and EGR is totally removed. Thumbwheel doesn't use O2 sensor and I doubt it uses EGR.

Something is rattling somewhere and causing the sensor to go off or else as someone suggested, there is a bad connection.

I'll post when I figure it out.

Thanks - Terry

 

[NJTurbo]

Great i just blocked off my EGR with the power plate and removed it. Running a Joe Lubrant 110 chip. I hope this is not EGR related, i will be pissed.