Another LT1 diagnosis thread
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Teching In
Joined: Aug 2014
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Another LT1 diagnosis thread Now i know its usual for everyone to point to the opti, and i myself have began to lean that way. I found other things during diagnosis just want to make sure I havent missed any steps. My oscope is dead and i am unable to scope signals until next Tuesday when SnapOn guy brings replacement.
Car has had random code 16, also had an ICM code 6 months back. It's been replaced, added new heatsink paste and did the ICM spacer mod. Even with the code 16 the car has ran great and the code would only show up during startup.
Last Friday omw home from work a buddy was behind me in his GTO on some backroads, i tried to push the pedal and the car fell on its face. I figured it was a misfire, or bad gas and the spark knock went to max..
Monday morning it was cool out and made it to work fine, but while sitting in parking lot waiting to punch in the car began to idle up to 1500/2000rpm and then back down. Meanwhile, the tach is bouncing... all i can think is oh shat.
Thats when i done the following:
Scanned with EEHack omw home, found the frames where RPM readout spikes to 4,000+ before the miss.
Tried running open loop to make sure it's not an o2/maf issue.
Fuel pressure was verified at 43psi primed, and 37-39psi idling
Checked for spark arc in garage with lights out.
Verified 10+ volts at ICM
O2, fuel filter were replaced last summer
Code 16 returned, i am fairly sure it's optispark. Time for an AIP Electronics opti review i suppose. I will test opti signals Tuesday before i replace it. No other codes present.
Car has had random code 16, also had an ICM code 6 months back. It's been replaced, added new heatsink paste and did the ICM spacer mod. Even with the code 16 the car has ran great and the code would only show up during startup.
Last Friday omw home from work a buddy was behind me in his GTO on some backroads, i tried to push the pedal and the car fell on its face. I figured it was a misfire, or bad gas and the spark knock went to max..
Monday morning it was cool out and made it to work fine, but while sitting in parking lot waiting to punch in the car began to idle up to 1500/2000rpm and then back down. Meanwhile, the tach is bouncing... all i can think is oh shat.
Thats when i done the following:
Scanned with EEHack omw home, found the frames where RPM readout spikes to 4,000+ before the miss.
Tried running open loop to make sure it's not an o2/maf issue.
Fuel pressure was verified at 43psi primed, and 37-39psi idling
Checked for spark arc in garage with lights out.
Verified 10+ volts at ICM
O2, fuel filter were replaced last summer
Code 16 returned, i am fairly sure it's optispark. Time for an AIP Electronics opti review i suppose. I will test opti signals Tuesday before i replace it. No other codes present.
Last edited by JustinSEO; Jan 24, 2018 at 07:46 AM.
TECH Fanatic
Joined: Jan 2015
Posts: 1,114
Likes: 33
From: Fort Worth, Texas
DTC 16 (Low Resolution) is usually the OptiSpark or corrosion at the jumper harness terminals.
The latest AC Delco remanufactured distributors have the Jumper harness sealed to the Cap & seem to last.
Make SURE the plug wires are in good shape & not touching the PS pulley or exhaust, One good short to ground through the plug wires will damage the distributor!!
The latest AC Delco remanufactured distributors have the Jumper harness sealed to the Cap & seem to last.
Make SURE the plug wires are in good shape & not touching the PS pulley or exhaust, One good short to ground through the plug wires will damage the distributor!!
Thread Starter
Teching In
Joined: Aug 2014
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Continued I did more tests on ICM and coil, signal to ICM was good.. coil was 9.9k ohm but had some corrosion on the terminal for coil wire, so i replaced it. Car ran well for a test drive, then omw to work it started acting really bad last 5 minutes or so. It was jerking hard, no power unless pressing throttle quite a bit.. had to force it to pull in to parking lot at work. When i popped hood at work the radiator was cracked also, so gonna have to tow it home and start tearing it down for an Opti.
there isnt anything left because i have ran it in open and closed loop, tested ICM, replaced coil, coil wire, pcm, and mostly everything else. I have been getting code 16s for awhile and its finally time to do it.
there isnt anything left because i have ran it in open and closed loop, tested ICM, replaced coil, coil wire, pcm, and mostly everything else. I have been getting code 16s for awhile and its finally time to do it.
Hope the replacement goes well. Every LT1 owner has to do it eventually. One bit of advice, with the new opti, open the cap and remove and reinstall the rotor screws with thread locker to prevent the rotor from detaching. Happened to me a long time ago on an opti that wan't very old.
P.S. I think you will get more responses faster if you post future engine questions in the LT1/LT4 subforum instead of the vehicle specific forum.
P.S. I think you will get more responses faster if you post future engine questions in the LT1/LT4 subforum instead of the vehicle specific forum.
Teching In
Joined: Apr 2016
Posts: 18
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From: Bloomington, IL
Assuming the new opti solved your problem? Was the opti an OEM opti or was it one of the AIP Electronics optisparks? I replaced my opti a while back with the AIP one and it's been solid since. I did have some weird ignition issues, essentially a misfire at 5500 rpm+ But after replacing the ICM all was well.
So anyway, talking in circles, was it an AIP Opti that failed on you?
So anyway, talking in circles, was it an AIP Opti that failed on you?
