Q: Replaced throttle body and now mpg has gone down. on 2003 Chevrolet Silverado 2500 HD

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I had a problem when the (low engine power) would come up in cool conditions but turn the engine off and it was ok. I replaced the throttle body as advised by repair pal and that problem is cured. I replaced it with an AC Delco body but now I seem that my mpg is down a little. Does the computer have to be reprogramed for this throttle body. Other than poorer mpg the engine runs great. Just wondering????
(2) Answers
(4) Comments
I didnt replace the throttle body gasket, it looked ok to me. The motor has about 94000 miles on it and I had the plugs replaced at about 80000 miles and the aircleaner is new. I know it sounds like I am nit picking about a drop of 1.5 mpg but if I drive easy I was getting almost 15mpg but not on the average. Im retired and this drop means a lot to me.
the gasket should have been replaced. you may have a vacuum leak that would effect your mileage.

You have other things going on. Like when is the last time you had plugs replaced, fuel injection service, fuel filter, checked air filter and scanned with scanner that can read serial data to look at fuel trims, upsream O2's so on and so on. Really one and a half MPG?
Again have you ignored what I posted. If you have a vacumm leak you would see that in the data stream. Of course that is based on the tech that knows what he is looking at. It is totally coincedental that your gas mileage has dropped 1.5 MPG. There's proablly preventive maintenance that you haven't performed.