Trouble code questions
Thread Starter
Racer
Joined: Jul 2013
Posts: 275
Likes: 1
From: Colorado Springs
Trouble code questions
1988 Corvette L98 4+3 Doug Nash
I took the car on the highway for a 1 hour drive at about 70MPH average speed. The Service Engine soon light popped on and the car went into limp home mode, as I got off the highway the car stalled on me. It started back up just fine, the Service Engine Soon light went away, but the car idled very low and almost stalled again.
On the way home the car did the same thing, after about 40 min of 70 MPH the Service Engine Soon light appeared again. Same results when I slowed down, but this time I did not let it stall...
I grounded the terminal A and B as show here:
http://www.corvettephotographs.com/c4vettes/ecm.htm
Retrieved codes 32 and 33.
32: Exhaust Gas Recirculation Circuit
33: Mass Air Flow Sensor Circuit (1985-1990)
Now I think the MAFS was stored from when I removed the AIR system, I started the car forgetting to plug in the MAFS and the car ran like crap and I soon caught my mistake...
Anyone have a next step, replace EGR? Something else?
I took the car on the highway for a 1 hour drive at about 70MPH average speed. The Service Engine soon light popped on and the car went into limp home mode, as I got off the highway the car stalled on me. It started back up just fine, the Service Engine Soon light went away, but the car idled very low and almost stalled again.
On the way home the car did the same thing, after about 40 min of 70 MPH the Service Engine Soon light appeared again. Same results when I slowed down, but this time I did not let it stall...
I grounded the terminal A and B as show here:
http://www.corvettephotographs.com/c4vettes/ecm.htm
Retrieved codes 32 and 33.
32: Exhaust Gas Recirculation Circuit
33: Mass Air Flow Sensor Circuit (1985-1990)
Now I think the MAFS was stored from when I removed the AIR system, I started the car forgetting to plug in the MAFS and the car ran like crap and I soon caught my mistake...
Anyone have a next step, replace EGR? Something else?
Advanced
Joined: Feb 2006
Posts: 54
Likes: 0
From: Reading Pa
Steady highway load the EGR spends alot of time open. It probably is sticking open. That will give you a bad low idle and stalling. Take it off and see if a piece if carbon is jammed in the pintle. Pieces of carbon build up in the exhaust ports and break off and get stuck in the valve. GM made an EGR gasket with a screen. I don't know if it is still available. Also, a low rough idle caused by a stuck open egr will set a maf low code.
Thread Starter
Racer
Joined: Jul 2013
Posts: 275
Likes: 1
From: Colorado Springs
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
The EGR does not work at full throttle, only during cruise. It cools the combustion chambers, which is not a bad thing.
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Team Owner
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From: SE NY
Cruise-In II Veteran
The ECM tests EGR operation shortly after startup; after steady throttle for a few minutes and coolant temps >173deg F it will call for EGR.
One way to eliminate EGR:
-Block off EGR ports
-Install a 160deg T-stat & fan switch. There will be no need for EGR.
-Connect a diode between the EGR command line to the Sol and the Temp Sw feedback line. This will fool the ECM when it does the initial EGR test
One way to eliminate EGR:
-Block off EGR ports
-Install a 160deg T-stat & fan switch. There will be no need for EGR.
-Connect a diode between the EGR command line to the Sol and the Temp Sw feedback line. This will fool the ECM when it does the initial EGR test
Team Owner
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From: Summerland B.C. Canada
Thread Starter
Racer
Joined: Jul 2013
Posts: 275
Likes: 1
From: Colorado Springs
I just do not see the value in installing a new EGR $50 when I am rebuilding the engine in 6 months. I do not plan on using the EGR in the new build... I removed the EGR and it was stuck 1/8th of the way open, no way to remove the debris in there. Probaly going to buy the block off plate and go from there.