apparent false spark retard 87 LG4
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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.
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.
#2
Supreme Member
Thread Starter
iTrader: (7)
Join Date: May 2004
Location: Lexington, SC
Posts: 5,291
Likes: 0
Received 58 Likes
on
52 Posts
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.
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