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apparent false spark retard 87 LG4

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Old 11-13-2007, 06:54 AM
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naf
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Car: 1987 SC/1985 TA
Engine: 350/vortec/fitech
Transmission: T56
Axle/Gears: 3.27 9-bolt
apparent false spark retard 87 LG4

Tracked an intermittent idle quality issue to timing. Timing appears to be hovering around 16-18 degrees and wavers. Occasionally when warm/hot the timing will jump up to the 'normal' 20-22 degrees and stay rock steady. After checking and testing new components from the ESC to the KS, I've done the following:

confirmed 9+ volts out of the ESC module on Pin C.
confirmed continuity from Pin C on the ESC connector to Pin L on the ECM
12 volt test light to ESC connector Pin C or Pin L on ECM, no change-no light
10 K ohm resistor across ALDL A and B results in smooth idle with 20-22 steady advance (I've read this disables the ECM's retard function).

Shop manual flow chart says if 12 volt light to Pin C doesn't work: loose connection/bad ecm. Replaced ecm with another 87 LG4 and no luck.

Is there a ground or other connection at ecm that could be at fault?

I struggled with hooking up WinALDL for a time, read up on some troubleshooting and saw a thread where it would work with the LG4 ecm but wouldn't read knock counts. My enthusiasm waned.
Old 11-14-2007, 06:27 AM
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naf
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Car: 1987 SC/1985 TA
Engine: 350/vortec/fitech
Transmission: T56
Axle/Gears: 3.27 9-bolt
Re: apparent false spark retard 87 LG4

Not even some words of encouragement? sheesh.
Old 11-14-2007, 09:53 AM
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Car: 82 Berlinetta/57 Bel Air
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Transmission: 4L60E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
I usually wait until naf comes in to answer these types of questions. . .
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