1992 LT1 potential ECM issues
Thread Starter
8th Gear
Joined: Dec 2020
Posts: 8
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1992 LT1 potential ECM issues
Ok, im going to get Specific. The car has had a trans issue from when i bought it a few months back, it likes to hold gears and has the occasional slip, the engine has had some sort of miss as well. The best way i can describe what the engine/trans is doing is it has a hesitation in acceleration noticeable on the tach, think of it pausing for a second then continuing to rise, ive noticed when stopped with foot on the brake just enough to stop the car it will lurch forward an inch with a pause in-between. The most recent issue is twice now when parked at in incline when i get back in the car it throws a check engine an ASR and the speedo, odo, and fuel level go wacky. when you drive the car when it does this the acceleration is retarded and the engine wont rev past 3000 RPM, ive read that people have had to bypass the security system and have had similar issues but they all have said the car wont start when it does this. MY only conclusion is that its ECU related, I believe its the ECU is in fact fried due to an aftermarket keyless entry being installed by the previous owner and consequently caused a miss or an issue with the trans. So now.... has anybody had the same issue as ive described or at least the same electrical issue?
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Trans isn't controlled by the ECM, so that immediately rules out the ECM relative to any/all of the trans concerns.
To ME it sounds like a poor/intermittent connection or ground, somewhere.
To ME it sounds like a poor/intermittent connection or ground, somewhere.
Le Mans Master
Joined: Aug 2015
Posts: 6,119
Likes: 1,994
From: St. Charles MO
Just to clarify for those reading this with later C4s, this is true through 1993 models. But starting in 94, the ECM became the Powertrain Control Module (PCM), and the trans control was contained in it. It can be tuned along with the engine calibrations using tuning software and by flashing the edited file to the PCM.
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
You could/should carefully remove the aftermarket add on. It's possible paperwork could be with owners manual depending on PO habits. Receipt would have installer and what was done related to bypassing pass key. If not it's somewhat of guessing.
warning lights indicate codes should be set.
92-93 LT1s all use the same ECM. They are also difficult to find used or on the shelf reman. "It takes one to get one" or your would have to be sent out for repair. What you're discribing could be an internal ECM problem. Use search feature, there are several recent threads related to the 92-93 ECM.
You should check grounds ECM grounds are clean and tight. There is no corrosion on ECM terminals or connectors. There's no coolant leak near Optispark ;since you discribed condition occurred when car was on inclined.
warning lights indicate codes should be set.
92-93 LT1s all use the same ECM. They are also difficult to find used or on the shelf reman. "It takes one to get one" or your would have to be sent out for repair. What you're discribing could be an internal ECM problem. Use search feature, there are several recent threads related to the 92-93 ECM.
You should check grounds ECM grounds are clean and tight. There is no corrosion on ECM terminals or connectors. There's no coolant leak near Optispark ;since you discribed condition occurred when car was on inclined.
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
Ok, im going to get Specific. The car has had a trans issue from when i bought it a few months back, it likes to hold gears and has the occasional slip, the engine has had some sort of miss as well. The best way i can describe what the engine/trans is doing is it has a hesitation in acceleration noticeable on the tach, think of it pausing for a second then continuing to rise, ive noticed when stopped with foot on the brake just enough to stop the car it will lurch forward an inch with a pause in-between. The most recent issue is twice now when parked at in incline when i get back in the car it throws a check engine an ASR and the speedo, odo, and fuel level go wacky. when you drive the car when it does this the acceleration is retarded and the engine wont rev past 3000 RPM, ive read that people have had to bypass the security system and have had similar issues but they all have said the car wont start when it does this. MY only conclusion is that its ECU related, I believe its the ECU is in fact fried due to an aftermarket keyless entry being installed by the previous owner and consequently caused a miss or an issue with the trans. So now.... has anybody had the same issue as ive described or at least the same electrical issue?
As mentioned by others, your transmission isn't controlled by the ECM (except for torque converter lockup stuff).
Invest in a factory service manual, they're about $20 on Rockauto, listed under 'literature' under your year, make and model. Then use it to undo whatever aftermarket nonsense someone tried to splice in. Get to a known good state. Then go from there.
Best of luck with the basketcase.
