LT1 Shutters and CEL
Thread Starter
Teching In
Joined: Dec 2007
Posts: 19
Likes: 0
LT1 Shutters and CEL My 95 TA had the check engine light come on a while back and today it started shuttering while driving and running rough (didn't think I would make it home). Put the scanner on it and got like 50 codes. Disconnected the battery and can't seem to make the codes go away. Just turn 100k so probably need to do a full tune up but want to address the issue and not just throw parts at it. Probably the Opti-spark but am looking for ideas. Thanks.
Thread Starter
Teching In
Joined: Dec 2007
Posts: 19
Likes: 0
tried a different scanner with the same results. Getting somewhere around 50 codes split between current and memory. If I rescan I get a similar number of codes some different some the same. Still can't get the codes to erase after leaving the battery unhooked for two days. Took the PCM out and cleaned the connectors, grounds and hot leads and made no difference. Trouble shot the knock sensor and eveything checked out fine. Starting to think the PCM is bad. So what is the "flashing" a new one entail? Took the access cover off the PCM and there was a little white "box" plugged in. Is that the "same" as the old chip for prior installations and would it be a matter of swapping it into a new PCM rather than "flashing" it?? Car still shutters/hesitates/misses during cruising and seems worse after it has warmed up. thanks,
TECH Veteran
Joined: Dec 2008
Posts: 4,147
Likes: 62
From: Little Rock, AR
Possibly is a bad PCM (or maybe a grounding or power issue?). Can't imagine that many codes at one time. The little white box is the knock module. Flashing takes a programmer or a laptop/PC, cable, software and a tune.
Trending Topics
If you know somebody with an LT1 try plugging it into their car and check for codes. Don't even need to start it. Lots of PCMs get replaced for no reason. Also plug the other PCM into your car and check for codes.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Thread Starter
Teching In
Joined: Dec 2007
Posts: 19
Likes: 0
about half of the codes are current and half memory. 13, 16, 28, 32, 37, 41, 41,43,44,45,46,47,53,55,58, 5961,63,64,65,75,83 current. 13,14,18,23,25,26,28,44,48,55,58,61,75,79,81,82,83 ,85 memory. even get 39,57,19,35,49,56,62 etc. that aren't even effective for me car. seems very weird to me that I can't erase them either so is why I was thinking the PCM. so where is the best place to get a new or used PCM flashed? thanks as always.
Is it modded or stock? If you have mods, I'd get PCM for less or some other mail order tuner reflash it for around $100 custom for your setup. Otherwise, I'd buy a used PCM off craigslist or a junkyard, or better yet find another LT1 owner nice enough to let them swap their PCM just to eliminate it as a cause.
Thread Starter
Teching In
Joined: Dec 2007
Posts: 19
Likes: 0
Unfortunately don't have anyone around with an F-body like mine (everyone wants a Toyota or Honda these days) that I can swap with. So for a used unit, does it have to be a 94 or 95 F-body with a manual trans PCM for things to work right???
Thread Starter
Teching In
Joined: Dec 2007
Posts: 19
Likes: 0
update OK, got a different PCM and got exactly the same results. CEL comes on and the car shutters while driving. Ran a scan and am still getting 50+ codes either present or stored using Shoeboxe's hook up chart. Would the opti spark going bad generate so many codes? Any suggestions/ideas would be greatly appreciated.
I already replied to your other thread....opti is toast, get a GM one or MSD 
EXCELLENT article on the intricacies on opti failures:
http://www.gmhightechperformance.com...ing_modifying/
EXCELLENT article on the intricacies on opti failures:
http://www.gmhightechperformance.com...ing_modifying/
