Mechanics

WHY WILL MY CAR HAVE TROUBLE STARTING IN HOT WEATHER AND GET BAD GAS MILEAGE?

2004 Chevrolet Malibu • 131,000 miles

My 2004 chevrolet malibu classic usually starts in cold weather but gives me trouble when it is warm outside. If it is warm outside the car has problems starting and will sometimes die while coming to a stop. It has lately been getting extremely bad gas mileage. Im only getting maybe 250 miles a tank. I have replaced fuel pump relay, fuel pump, spark plugs, fuel filter, fuel pressure regulator, and was told to check asd but it is built in with the fuel pump relay. So I do not think it is that. Also when the car is not starting I do not here the fuel pump prime, which thought could be bad wiring but bad wiring shouldn't cause bad gas mileage. Was told by one mechanic it could be a bad sensor, but which one would give all of these problems?
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Robertschnitker
December 6, 2011.



Usually bad gas mileage is related to Oxygen Sensors going bad or a leak in the exhaust near them. The fuel pump prime is hard to hear. You may need a second person to get near the tank and listen for it.
The other issue may be the idle air control valve which keeps the idle steady by opening ports to change the mixture. If it is stuck in a rich air/fuel ratio setting, that may be why the car gets bad gas mileage. It may need to be cleaned or replaced.
You may also have a weak coil. Test the coil and see if it is bad.

An ASD relay is something used on Chrysler vehicles, not GM. You really need a good scan tool here to be able to see all the sensor data to look for something out of place. You could see if the computer is trying to compensate for a rich condition or if one of the temp sensors is not reporting accurately.
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Wrenchtech
Dec 7, 2011.

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