I own an 88 S-10 blazer, its a 4x4 2.8L. It runs great and has very low miles on it, less than 85,000. But recently it started eating gas. Before I used to get 20mpg, and now suddenly I'm only getting right around 10mpg.

I can't figure this out: I've had the cat hollowed out awhile back and the O2 sensor is almost new. The EGR valve has been changed, TBI cleaned, and within the last year I've changed the wires, plugs, cap, etc... Its rated to have r-15 190s on it but I have r-15 245s on it, I don't know if this is the problem or not, but its all I can think of.

At first I thought it was the fact the gas tank had a leak and a fuel line was rusted through, but over the weekend I fixed both and its still eating gas. 3/4 of a tank of gas has only got me around 210 miles. I used to get around 400 miles per tank, but now its just eating gas. I would hate to get rid of my blazer, it runs great, has always been dependable, and has low miles on it but gas isnt cheap.

I went ahead and bought a fuel filter, which looks like its gonna be a pain to do, and an air filter to replace over the weekend. Maybe this will help. I'm also planing on pulling the plugs to see what they look like. I was told on another forum to replace the cat and that this is the problem. If thats true is it just a lack of back pressure? The exhaust doesnt crackle or even get loud like it needs more back pressure...

CAN ANYBODY PLEASE HELP ME WITH THIS????

 

You said that You changed to a different tire. What type of tread design does it have? If it's an aggressive off road type, it'll kill mileage especially in light of the 2.8L engine having to push that tire around.

 

The tires are just Uniroyal R-15 245s. They arent some monster Super Swampers or anything. They fit right on the stock rims, I have a set of old rims maybe I'll get some used tires and try it on smaller tires. I was told to check into the TBI, so I'll look into that too.

 

the tires will contribute a bit as there is more rubber on the ground to push along the road, but not 10mpg difference.

I would suggest add a bottle of injector flush to a tank of gas as well, since you have a new EGR, your injectors may still be clogged a bit.

 

after changing the plugs wires cap rotor, again, the problem still exsist. so now i've been told that it could be the MAP sensor and/or the idle sensor..... not sure on this. ANY ADVICE FROM ANYONE????

also had a friend advise me to run a bottle of tranny fluid through it, personally i thought this sounded a lil redneckish...

 

Running tranny fluid thru the engine will clean a lot of the carbon off. You just want to make sure you don't pour it in so fast that you kill it. Or if you don't care about the smoke you can put a quart in with a full tank of gas. It will smoke untill that is burned off though.

 

Changed the temp sensor, but not the map sensor. This was the advice of the parts store, sense the first diagnosis reading came back low voltage to the MAP sensor, so I replaced the teamp sensor and went back to the parts store, The second diagnosis came back and didnt come up with anything and it's still eating gas.

The exhaust smells rich and I'm guessing that you can't manually adjust a throttle body they way you can a carb. Running out of options here, any ideas??????