'99 Rodeo - Poor Gas Mileage, Knocking

[jcomeaux]

I have a 1999 Rodeo with about 42k miles. I have noticed some engine knocking when accelerating, and also poor gas mileage. Anyone have a similar experience or have an idea of what is wrong?

One reason I ask is that my nearest Isuzu dealer is over an hour away, so I would like to bring it to a local repair shop, and I would like to be able to give them a better idea of what is possibly wrong.

Thanks,
Jeff

[rodeo02]

Some knock/ping (detonation) is normal during heavy acceleration. Some brands of gasoline can cause more knock than others. A failing EGR system or carboned up combustion chamber can also cause detonation. These engines need to have fuel system cleaners run through them regularly. Run a 20oz bottle of chevron techron concentrate (or equivelant) in a full tank of gasoline every 3-6Kmi or so. Poor MPG's could be caused by failing O2 sensors- but you would likely get a "check engine" light if one of those (4) was bad. 20mpg's is about the best you'll get with the 1998+ 3.2L, if you are consistantly getting less than 15mpg w/ EASY driving, there may be a problem. Make sure your tires are aired up to door jamb sticker specs. Make sure your air filter is clean, & run good quality gas. Running with the a/c on or windshield defrost will kill your MPG's as well. Pull, inspect/replace & relube the spark plugs by 40Kmi as well. MAKE SURE you've changed out the ATF by this point too- if you have an automatic tranny. G/luck
Joel

[daze]

I agree with last post...check and replace 02 sensors. I just replaced one on my mazda and it makes alot of difference. Are you getting any CEL (check engine lites) coming on at various speeds? If so, you're prolly running too rich and burning more fuel. Changing plugs and 02 sensors should do the trick.