LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

runs fine, then acts like bad gas, backfires chugs. dies throws check engine light

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Old 02-09-2008, 11:08 PM
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runs fine, then acts like bad gas, backfires chugs. dies throws check engine light

Had a hesitation last night at the track (second time, first was day before after car idled for 15 min) I would punch it to take off act like plugs were loaded up from idling. Never happened til friday night at the track. nailed gas on green, hesitated and then took off. Tonight was going to cruise in, car started to buck and snort and act all screwy, like i had water in the tank. service light came on car ran fine, no problems. Stopped off at parts store , put in some fuel treatment, restarted car service light gone car ran fine. 5 mile later, it bucks and snorts all over again, pops through exhaust like a major misfire, light comes back on car runs fine. I got to car show, parked it for several hours. Fired right up, drove about 5 miles, misfire symtom comes back. Light comes on car runs smooth again. This happened everytime I'd shut car down and inspect it. I got to a friend whos a tech, while it still had the light on, the scanner showed no codes currently, history showed a 16. Car ran fine , stopped at gas station. Topped tank with new fresh fuel. Car ran like crap. Let it idle 5-10 min, light came on smoothed out drove home. I researched on like, found my answers. Is this optical module do this? run like crap then run fine after the codes/ engine check light comes on?
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Old 02-09-2008, 11:12 PM
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Yep, sounds like a dying opti.
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Old 02-09-2008, 11:13 PM
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opti module?
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Old 02-09-2008, 11:15 PM
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Optispark (distributor).
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Old 02-09-2008, 11:18 PM
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Check the Opti harness connectors for corrosion and/or damaged pins.

Sounds like heat is the enemy. Could be the optical module in the Opti, may also be the IC Module.
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Old 02-10-2008, 12:38 AM
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not 16!!


all you need now is the matching 36 and your all set!
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Old 02-10-2008, 12:39 AM
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LOL I don't even wanna know what 36 is, guess tomorrow (today) I'll start simple and go IC first. Well on a positive side at least I know why I slowed to 7:9's friday night
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Old 02-10-2008, 01:00 AM
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so why does the car go back to running fine with the SES light on?
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Old 02-10-2008, 05:38 AM
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Originally Posted by wyldcdn
so why does the car go back to running fine with the SES light on?


Because it goes into limp or back up mode. If you can get it to my house on Monday I have a scan tool, when is the last time you cleaned the MAF?

David.
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Old 02-10-2008, 07:27 AM
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man that would be sweet. I cleaned MAF.....5-6 months ago. Gonna try IM first. *SIGH* Like i said jokingly at least it explained the surge stutter this past friday night.
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Old 02-10-2008, 11:11 AM
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code 16 doesn't get set off cause something else is broken.
16 and 36 don't play games!!


i spent a week doing alot of wishful thinking troubleshooting, but reality always came back to kick me in the ***.
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Old 02-10-2008, 11:17 AM
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meaning with the 16 code?
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Old 02-10-2008, 12:00 PM
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16 and 36

low res
high res


i forget which goes with which code but its the electronics in the opti.
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Old 02-10-2008, 12:19 PM
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Code 16 is the distributor. Don't waster your money on the other crap. i just went through the same thing a few weeks ago. Got a 16. Then a 36 too. Only did it when the engine got hot. The heat made the bad electronics in the opti rear its ugy head every time. A new opti will fix you up. Check the opti cable too. mine looked like brand new still, but you could have a bad cable too.

I have a cable and a laptop if you wanna come up to Bay Minette to scan it.
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Old 02-11-2008, 04:00 PM
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Originally Posted by Injuneer
Check the Opti harness connectors for corrosion and/or damaged pins.

Sounds like heat is the enemy. Could be the optical module in the Opti, may also be the IC Module.

He came over today, I put my old opti harness on it and the low res code went away. Has a 36 and a 42, I can clear the codes start the car and it pops and backfires, the check engine light comes on and it clears up, runs TOTALLY like normal. Never seen anything like it.

When the check engine light comes on, does it use it's own high res pulse in a backup table in the ecm?



David
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