[Gmecm] 1990 Cavalier 3.1l running very rich, ECM?

[J M]

Not sure if I'll be much help, but one of the simple checks to rule out first would be the coolant temperature sensor.? Have seen them fail making the ecu believe the engine is far colder then it is.? Also check the wiring from the sensor to the ecu for high resistance.

After that I'd look at the MAF or MAP sensor (whichever it has).? 

Maybe check the firing order?? That probably has coil packs so might not be a problem... or dead coil?

Have had similar problems with a few different GM cars, never as bad, and on a cbr600 engine running salvage yard GM sensors and a Performance Electronics ECU.? The PE saw a engine temp of -100F on a 90F day, wouldn't even try to run, hydro-locked after some other guys tried to start it.

Good luck.

Jason M.

--- On Thu, 11/18/10, Cowen <captain_krill at yahoo.com> wrote:

From: Cowen <captain_krill at yahoo.com>
Subject: [Gmecm] 1990 Cavalier 3.1l running very rich, ECM?
To:
 gmecm at diy-efi.org
Date: Thursday, November 18, 2010, 7:14 PM

Hello all, I'm having trouble diagnosing a student's car.? He's resurrecting a car that came in not running and, after doing a bunch of top end work, it's running now, but very, very rich.? It will barely idle, and the SnapOn MODIS reportsO2 voltages around 950mv most of the time, especially at lower RPMs, and the integer is usually around 120 or lower.? It is entering closed loop.? So, the ECM "knows" it's running rich, and it's pulling fuel from the mix, but not enough.? You can smell the fuel when it's running, the cat can't keep up!




      
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