Spark Retard(ed)
10-01-2007, 03:56 PM
#1
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Member Since: Mar 2007
Location: Palo Alto CA
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Spark Retard(ed)
I've been logging with Datamaster on my 95 and I've been learning about tuning my own car while hunting down a phantom knock. I believe I have a rattle somewhere in the car that is getting picked up by the knock sensor and it's pulling out a lot of timing. Almost 10 degrees in some cases. 
I'm even seeing spark retard when it's not incrementing the knock count?! Not sure what is causing that. I installed an LT4 knock module and the knock count has gone down quite a bit, but I still got it. So I decided to try a tank of 100 Octane unleaded. Yes, I ran the tank down until the check gauges light came on and I had NO bars left on the digital display, the range just said LO. And I still got knock. So now I'm pretty sure it's not real knock, because I can't see how a stock N/A LT1 could knock with 100 Octane.
My question is this. Would it be safe to remove all the knock retard from the ECM and other than Max. Knock Retard Vs. RMP (in P.E.) & (Not in P.E.) are there any other tables do I need to modify?
Thanks.
I'm even seeing spark retard when it's not incrementing the knock count?! Not sure what is causing that. I installed an LT4 knock module and the knock count has gone down quite a bit, but I still got it. So I decided to try a tank of 100 Octane unleaded. Yes, I ran the tank down until the check gauges light came on and I had NO bars left on the digital display, the range just said LO. And I still got knock. So now I'm pretty sure it's not real knock, because I can't see how a stock N/A LT1 could knock with 100 Octane. My question is this. Would it be safe to remove all the knock retard from the ECM and other than Max. Knock Retard Vs. RMP (in P.E.) & (Not in P.E.) are there any other tables do I need to modify?
Thanks.
10-02-2007, 08:30 AM
#2
Le Mans Master
So now I'm pretty sure it's not real knock, because I can't see how a stock N/A LT1 could knock with 100 Octane. Would it be safe to remove all the knock retard from the ECM and other than Max. Knock Retard Vs. RMP (in P.E.) & (Not in P.E.) are there any other tables do I need to modify?
Since you state everything is stock, I would be looking at those rattles you mention, or other suspect noises. Only if I found it wasn't a mechanical or other issue, would I then tweak timing table and or fuel based on what I was seeing in scans. I have had other things attribute to SK., such as sudden blm shifts (both rich and lean), carbon tracked cap, conv. locking, have all caused spark knocks.
10-02-2007, 09:29 PM
#3
Melting Slicks
FYI... When I installed the LT4 module in my '95 my knock counts went nuts. It would count when sitting in neutral and varying the RPM. I could find the sweet spot and bam, almost continuous counts. I figured it was picking up my roller rockers. No problem with the LT1 module. I tried two LT4 modules, both new from the dealer, same result. I know some others have not encountered this, so maybe there is a difference between early and later '95 PCMs?? Just a guess.
