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I have been getting 14 MPG since I purchased my 1992 Rodeo and live at close to 5000' (Altitude). I took a trip last weekend down to sea level and got 20 MPG with a lot of in town driving. It had power going up hills and picked up speed very quick on the freeway. I just filled up the tank and am back at 5000' and have dropped to 16 MPG and am back to going up hills slow and when I step on it there isn't the response there was at sea level. Now I am disappointed because I know what it is capable of. My question is can you change the jets on the carb., if so to what?...also is there anything else that I could change to get the better MPG and power? I have another question about the spare tire rattle. Any way to fix this or atleast lessen it? Thanks so much, Sheri
 

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You have EFI (it's GM Throttle Body Injection) and unless something is drastically wrong with the MAP sensor or other emissions parts, it will compensate for altitude. However, air closer to sea level is denser and will make more power regardless. Loss of power at hi altitude is inevitable but you can do a few things to perk up the old Beast.

Check out this great article at the Outdoor Wire Isuzu site on getting more out of the GM 60 deg V6:

http://www.4x4wire.com/tech/60degreeV6/

Anything you can do to improve airflow will help with power and mpg.

Just flipping the lid of your air cleaner upside down will let more air into the air cleaner. Although it'll be a bit noisier, you should notice a definite difference in performance from 3500 rpm and up.

A less restrictive exhaust will also do wonders. A 2-1/4" cat and free-flowing exhaust will let the motor breathe. Lots of folks are happy with the Dynomax Hemi Turbo Muffler. You can get a new cat and the Dynomax for a good price at www.summittracing.com and have a local exhaust shop do the installation. This is probably the most important improvement you could make, because the factory exhaust system is very restrictive and these motors respond well to breathing improvements.

Check out this good discussion on mufflers at the Wire:

http://www.4x4wire.com/forums/showflat. ... 14&fpart=1

You can adjust the ignition timing setting from its stock value of 10 deg BTDC to 14 or 15 deg BTDC. This'll perk the motor up a bit more.

A K&N or other type of free-flowing filter may help. I've also seen a K&N Filtercharger replacement air cleaner top that has a filter element in it, this would drastically improve airflow into the TBI.

Try changing the O2 Sensor, if you have a lot of miles it may need it anyway. They are a relatively inexpensive GM-type 1-wire sensor that should be available at just about any auto parts store around. This sensor sticks straight up out of the exhaust pipe, just in front of the catalytic converter. All you need is a wrench to change it.

Anyway, short of moving to lower elevations (!) about all you can really do is optimize what you have.

HTH and let us know how things go.........ed
 
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