1989 Corvette ECM issue
Thread Starter
5th Gear
Joined: Jun 2025
Posts: 5
Likes: 0
From: Massachusetts
1989 Corvette Idle and Misfire Issue
Hey everyone, I'm new to this forum but have been using it help with a lot of things on my car over the past few years, so thank you for all of the knowledge. My car (new to me 2 years back) is a 1989 L98 Corvette with 52,000 now. So to the problem, over this winter I took the intake apart to seal an oil leak on the rear china wall, and replaced parts along to way to get the car sorted including new injectors. After setting the timing and plugging the ECM in, I kept having intermittent misfiring and occasional stalls at stops. This led to adjusting the timing over and over, and finally to looking at buying another set of injectors or a fuel filter to chase fuel pressure (which hasn't been diagnosed yet). Today just to check, I unplugged the EST connector, because the car idled better with it unplugged, and no misfiring on the next drive. The base timing seems to be pretty close, with the car running near perfect with the EST unplugged, but obviously the ECM is getting a bad signal for somewhere that is throwing timing off once the EST is plugged back in
So at this point I'm wondering if there is something wrong with ECM, or something else but I am stumped. Any help is appreciated!
So at this point I'm wondering if there is something wrong with ECM, or something else but I am stumped. Any help is appreciated!
Last edited by Cindeck; Jun 20, 2025 at 09:38 AM.
Cruising
Joined: Sep 2021
Posts: 11
Likes: 2
From: Florida
Ecm issue
You mentioned that when you disconnect the est connector it runs better.
Did you disconnect it before setting the base timing?
Also, if you have access to a scanner check the knock counts to see if they are high. That will also retard timing and could cause performance issues.
Did you disconnect it before setting the base timing?
Also, if you have access to a scanner check the knock counts to see if they are high. That will also retard timing and could cause performance issues.
Thread Starter
5th Gear
Joined: Jun 2025
Posts: 5
Likes: 0
From: Massachusetts
You mentioned that when you disconnect the est connector it runs better.
Did you disconnect it before setting the base timing?
Also, if you have access to a scanner check the knock counts to see if they are high. That will also retard timing and could cause performance issues.
Did you disconnect it before setting the base timing?
Also, if you have access to a scanner check the knock counts to see if they are high. That will also retard timing and could cause performance issues.
Thread Starter
5th Gear
Joined: Jun 2025
Posts: 5
Likes: 0
From: Massachusetts
Last edited by Cindeck; Jun 21, 2025 at 09:26 AM.
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