[spd214]

Driving a 1994 Corvette Coupe, LT-1 Engine. Replaced Cooling Fan Assembly, new Thermostat, Cleaned Mass Air-Flow Sensor, and Replaced Coolant Temperature Sensor, and a new set of Injectors & new EGR Valve, New Spark Plugs (stock) and wires. I have a check engine light that comes on and goes off periodically. The weird thing is this, when the check engine light is on the engine smooths out runs better, and does not run rich. When the engine light goes off, I notice that the engine runs rough, and rich. I had my wife drive the Corvette and followed her in her car. I noticed that when she would stop, the exhaust was black in color when stopped and idling at stop sign or stop light. Then after awhile I noticed that the car was not putting out black exhaust at a particular stoplight. The check engine light came on at that time and the engine smoothed out. Gas milage is averaging about 12mpg in city. I had a mechanic hook the Corvette up to a computer when the check engine light was on and he said that he could get no reading at all. Not sure if he knew what he was doing. Any ideas what about what might be causing the engine to run rough and rich when check engine light is off, but run smoother and proper when the check engine light is on. Corvette has 104,200 original miles. Belonged to my uncle, and I purchased it from his estate.

[94aquavette]

It still sounds to me like a mass air flow sensor problem. While i'm fairly new to corvettes, i've been a mechanic for over 15 years, and i've found cleaning them usually doesn't help anything once they go bad, and the problem may be in the part of the meter that's sealed up that you can't clean. Try unplugging the sensor and see if the car runs. If it does, carefully drive it in an area where you have no traffic to worry about and see if your problem improves. Of course, if it runs with the sensor unplugged, you will have a service engine soon light on all the time, but it will tell you if your sensor is bad or not. The other solution of course is to just replace it with a new or a known good sensor. Good luck hope this helps.

[spd214]

Thanks 94Aquavette: Took your advice, and I believe that you properly diagnosed my problem. I disconnected the mass airflow sensor, and noted that the car ran better than when it was connected. I have ordered a new mass airflow sensor.

[94aquavette]

Anytime, glad i could help!