Engine Performance problem
2003 Chevy Impala 6 cyl Front Wheel Drive Automatic 204000 miles
My car randomly has engine surges/stumbles that, once they begin, will get worse and eventually become so severe that it will stall. I have to try and try to get it restarted and then limp home. Sometimes the car is better the next day, sometimes in two or three days. Then I can drive it again, but sooner or later the trouble starts again, usually within about 50-60 miles of mostly highway driving. There is no check engine light and no trouble codes even when it cuts off. I have changed the fuel and air filters. It passed all the fuel sys and vacuum tests I did on it, even when having the problem so bad I would sometimes have to restart it to continue the tests. I suspect a bad MAF sensor, but can't prove it. When running, none of its numbers seem noticibly off on my scan tool. However, I get readings from it when the engine is off and the key on--when I assume it should read 0.0 like my Mazda and Toyota. It usually scans betwen.2 and.5 lb per min with teh engine off, but has given readings of 6.4, 11.7, and even 20.4 (not accurate even if I was running 100 mph). The reading stays steady as long as I have the key on, but turn the key off and then on again and the reading changes to another random number. Crank the car, and it goes to normal idle numbers like.4 to.6 lb. This continued even after I cleaned the sensor wires. Are the false engine-off readings a sign of a bad sensor or is there another problem with the car?
have the same problem?
Saturday, April 11th, 2009 AT 3:55 PM