question for you guys, apparent false knock
11-17-2007, 01:56 PM
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Car: 1987 SC/1985 TA
Engine: 350/vortec/fitech
Transmission: T56
Axle/Gears: 3.27 9-bolt
question for you guys, apparent false knock
This is not specifically DIY prom stuff but I've gotten as far as I have searching and most of what I've learned came from this board. The Tech/General board didn't help.
Far as I can tell my 87 LG4 spark retard is similar to the TBI setup but does not incorporate the KS test and my system has not thrown a SES code 43. Anyway:
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?
Any help is greatly appreciated.
Far as I can tell my 87 LG4 spark retard is similar to the TBI setup but does not incorporate the KS test and my system has not thrown a SES code 43. Anyway:
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?
Any help is greatly appreciated.
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