does the PCM factor in anything else to determine how much timing to pull, or is the knock sensor the only sensor it uses to determine this.

Thanks
Brian

 

It's the only sensor in "knock" but a couple of stradigys use it for there purpose.

 

The "knock" is picked up by the knock sensor in the block. The data is transferred through the one wire to the knock module. The module receives the data, interprets it and translates/sends it to the PCM.

A problem in the knock sensor circuit can be caused by any of these. (KS, wire, KM or PCM)

 

thats what I figured, but I was thinking that maybe the PCM could use other factors, like a combination of maybe misfire detections, rich/lean conditions, or some other engine problem that would cause the PCM to pull timing.

The reason I ask is I tried to disable my OBDII knock sensor and it still pulls timing the same way whatever I try, like maybe the PCM is reacting to other engine conditions.

Brian

 

im not sure what does the actuall pulling of the timing, but you can have timing retard from the map sensor in an abrupt change in maniflod absolute pressure (map) but that more comonly found in six speeds

 

You're talking about burst knock, and that is true, but he has a different issue.

 

I believe that the temp reported to the PCM by the IAT (intake air temp sensor) can also cause timing to be pulled.

 

I believe there is also a low octane gas timing pull

 

Correct, there is air temp correction.

 

How do you tune this out with LT1 edit other then zeroing out the knock?

 

There appears to be a 3deg adjustment to the timing the PCM sets, based on IAT reading, but I don't think that shows up as "knock retard".... it just doesn't get added on top of the value the PCM pulls off the timing map. Appears the person asking the question is seeing knock retard, even though he feels he has "disabled" his knock sensor.

How did you "disable" it? If you didn't do it correctly, the PCM may feel the KS is not working, and use a default knock retard calculation, that will result in almost constant knock retard showing up.

 

The only two that I know of, other than KR from knock, is low octane KR and burst KR. Anything else won't show up as KR. Of course, things could be different for a 96, as I am talking about the '8051 PCM, but my understanding was most things are the same.

As far as I can gather from watching datamaster and looking at logs, Low Ooctane KR will happen when the PCM sees repeated knock events. It figures "I am getting crazy knock all the time here...maybe he put in low octane gas..." so it will pull SA (spark advance) per the low octane mode tables. There are rpm and MAP tables for this (i.e. it pulls less timing at lighter loads when in Low Octane mode). I zero'd mine out. I feel the knock sensor, knock module, PCM and opti work fast enough to eliminate the need for any preemptive measures (obviously GM felt differently though). My biggest problem with Low Octane mode is, it doesn't *seem* to learn at what RPM/load the repeated knock occurs. It just applies Low Octane mode to any RPM and load. So if I got repeated knock at 5000rpm, 95kpa, enough to trigger Low Octane mode, it will still pull spark at 2000rpm and 70kpa according to what the tables specify. This I didn't like. Basically, I was losing performance in areas where I never had any KR to begin with.

Burst knock retard is a different animal and I don't fully understand it (in terms of WHEN it "kicks in"). It is similar to Low Octane mode in that it's a preemptive measure but it's based on transients (either the MAF or MAP or both). I think I left mine on but I'd have to double check.