intermitant electrical problem
Thread Starter
5th Gear
Joined: Feb 2010
Posts: 5
Likes: 0
From: Rockaway N.J.
intermitant electrical problem
Hi I have been looking through posts recently to try and figure out a problem I am having with my 1989 corvette convertible. Hopefully I can get some guidance here. My car sat for roughly ten years and I got the car running a couple of months ago. I was getting a maf code and a timing code. I have since fixed the maf issue.I have installed a new maf, maf relays, plugs, wires, cap, rotor, coil. I also checked the timing which was right on.
the car was originally running like crap but the car now runs awsome just like it used to. but I still am getting an intermitant code from time to time. it is a code 42. I want to change my e.s.t. sensor within the cap rotor assembly but someone also suggested it could be my ecm. how could I test to narrow down which could be causing the problem? right now the car runs great but every couple of days it seems like someone is flipping a switch while I am driving it on and off. the car doesnt die but it sets off the code then if I let off the gas it seems to clear itself like nothing ever happened.... Any suggestions would be greatly appreciated...
Burning Brakes
Joined: May 2007
Posts: 965
Likes: 13
From: turn 12 at Road America or TX
Sounds like an electrical connector pin issue. Check the EST connector for any corrosion - use magnification is possible. Does the issue seem to be temperature related; ie., does the problem happen only when the underhood temperature is high or low? If high, it could be the EST module itself. The ECM is another possibility ... but I don't know how reliable that unit is. Anybody?
Thread Starter
5th Gear
Joined: Feb 2010
Posts: 5
Likes: 0
From: Rockaway N.J.
gbrtng it does seem that this issue occurs when the car is warmed up but as I stated some days the car runs like a raped ape and out of nowhere someone is flickin a switch and the engine is cutting in and out..... Maybe I will just change the est module... I thought there might be a way to diagnose before just replacing one or the other.
Burning Brakes
Joined: May 2007
Posts: 965
Likes: 13
From: turn 12 at Road America or TX
Would set 3 completely unrelated codes and after my friend spent an hour with his Tech 1 I decided to replace the EST. No good, same problem. Picked up a rebuilt ECM from a junkyard, popped the MEM-CAL in it and all has been OK for 4 years or so. Turns out the 91 ECM is a common GM part across 10 carlines or so. Don't know about the 89 however.
Instructor
Joined: Feb 2008
Posts: 177
Likes: 5
From: Toronto Ontario
I had an intermittent ECM in my 91 - drove me nuts trying to diagnose it.
Would set 3 completely unrelated codes and after my friend spent an hour with his Tech 1 I decided to replace the EST. No good, same problem. Picked up a rebuilt ECM from a junkyard, popped the MEM-CAL in it and all has been OK for 4 years or so. Turns out the 91 ECM is a common GM part across 10 carlines or so. Don't know about the 89 however.
Would set 3 completely unrelated codes and after my friend spent an hour with his Tech 1 I decided to replace the EST. No good, same problem. Picked up a rebuilt ECM from a junkyard, popped the MEM-CAL in it and all has been OK for 4 years or so. Turns out the 91 ECM is a common GM part across 10 carlines or so. Don't know about the 89 however.
Look at the "Detailed Applications" portion of the following link
http://www.cardone.com/English/club/...ARTNUM=777165#
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Thread Starter
5th Gear
Joined: Feb 2010
Posts: 5
Likes: 0
From: Rockaway N.J.
thank you so much for your help everyone. I guess I will start looking for a ecm and a copy of the fsm for my car. my brother in law is a mechanic and has access to some good programs for diagnosing but I am sure the fsm will help me.
Once I have changed out the parts and have figured out the problem I will post my fix. this intermittent stuff is a pia to diagnose without dropping alot of $.....
Once I have changed out the parts and have figured out the problem I will post my fix. this intermittent stuff is a pia to diagnose without dropping alot of $.....
Thread Starter
5th Gear
Joined: Feb 2010
Posts: 5
Likes: 0
From: Rockaway N.J.
If anyone has suggestions to where I can find one from a trustworthy person or place that would be appreciated as well. When buying a used one how can I trust it is a good one and the right one for the car. I just saw one on e-bay for 250.00 for a 4+3. but I am not sure if my car is a 4+3 . I think that refers to the transmission right?