2000 Chevy Impala poor gas mileage

JAMES2000

MEMBER
2000 CHEVROLET IMPALA
6 CYL
FWD
AUTOMATIC
86,000 MILES

We have owned the car since new. In the past 2 years the gas mileage has gone from 22 - 24 to 18. We have had it to the dealer and spent money for a tune up new plugs fuel filter ect. There are no codes. They can find nothing wrong. Our driving hasn't changed. I have found oil on the top of the manifold and not sure where it is coming fromThe mileage is horrible any ideas?

Thanks Jim

6 Replies

AIRSOFTSOLDRECN9

MEMBER
348 POSTS

Oxygen Sensor(s), Catalytic converter, EGR valve could be potential problems. If the valve cover is leaking oil you will need to replace the gasket. Do a compression check on the engine just to be sure.

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Monday, June 23rd, 2008 AT 2:33 AM

JAMES2000

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I changed the egr about 6 months ago and that changed nothing. I am in for smog this week. We will see what the readings are. Both o2 sensors are almost impossible to remove.

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Monday, June 23rd, 2008 AT 8:43 PM

AIRSOFTSOLDRECN9

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I am not sure what state you live in but in Texas they keep your inspection fee if you do not pass until you are able to fix the car. If you can not fix it in 30 days. Well sorry. Most likely it is your catalytic converter.

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Monday, June 23rd, 2008 AT 9:22 PM

JAMES2000

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Hi I just got back from smog check and all 1-4 are at zero emissions and the other is at 1 or 2. So things are working properly and yet I still only get 18 mpg. Strange?

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Monday, June 30th, 2008 AT 4:12 PM

AIRSOFTSOLDRECN9

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348 POSTS

Is your transmission in good order? Has the fluid been changed? If not then do so and use a good synthetic. Try a synthetic in your motor oil too as it will add significantly to your gas milage. Use a high detergent gasoline for awhile or purchase some seafoam from the parts store. It will clean out excess carbon deposits from your valve stems, intake manifold and combustion chamber. Follow it as directed.