19 Degrees Of Knock Retard
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Joined: Mar 2003
Posts: 28
From: Birdsboro, PA
19 Degrees Of Knock Retard
Well today I played round with the new Snap-on Diagnostic toy, and was unhappy with what I saw. With key off diagnostic I pulled a code 16 which had to do with the 4 pin connector on the opti-spark. It said the ECM was getting false readings, unable to process it. Then I ran the key on, engine running and driving mode, I monitored the knock sensor and degrees retarded and it many of times I got 17 degrees + of knock retard. And that is under slow acceleration, well moderate, maybe half-3 quater throttle. Where is this coming from? I never run less than 92 octane, usually with a half gallon of xylene. Can you guys hit me with any pointers on any of these problems? Is it the false reading from the Opti spark that is causing the false knock? Im stumped and rather disgruntled. Thanks!
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Joined: Nov 1998
Posts: 71,121
From: Hell was full so they sent me to NJ
DTC 16 is "loss of low resolution pulse from the OptiSpark distributor". That had to be a "stored" code, because if you lose the low resolution pulse for 2 crank revolutions, the PCM shuts down the fuel pump and injectors - engine obviously stops. It is not unusual at all to see this "stored" code in a scan.
If the engine is running, I'd be inclined to think the same way as Madwolf.... you were looking at the spark advance readings, maybe, rather than knock retard. Some scanners show ignition timing as "-" to indicate "advance". I don't even have a KS (I don't use the stock PCM for igntion timing) and the default values for knock retard with a KS fault don't go much over 12deg. There is actually a field in the PCM program that limits the maximum value of KR, and I don't think its as high as 19deg.
If the engine is running, I'd be inclined to think the same way as Madwolf.... you were looking at the spark advance readings, maybe, rather than knock retard. Some scanners show ignition timing as "-" to indicate "advance". I don't even have a KS (I don't use the stock PCM for igntion timing) and the default values for knock retard with a KS fault don't go much over 12deg. There is actually a field in the PCM program that limits the maximum value of KR, and I don't think its as high as 19deg.
Thread Starter
Registered User
Joined: Mar 2003
Posts: 28
From: Birdsboro, PA
Im positive I was looking at the knock retard values. Timing advance was right next to the retard display, advance was usually 11 deg. I am not saying this computer is always right, but being from Snap-On with a price tag of $3000 it darn well better be accurate. Ill have to do another run I suppose, but any suggestions would be great. Thanks.
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