Ok I have a 98 blazer with 140K miles on it. I recently started having fuel mileage problems. I replaced the Cat beacuse it was killing me rattling like hell. My next thought is the fuel filter, and if that doesnt cure it then go for injectors. Is there anywhere that sells an injector kit? or do you have to buy them seprately ? I checked the auto parts store and they are like 70 dollars a peice and I find that outrageous. Also how about the O2 sensor? I see that it has 3 of them. Is there anyway to tell if just one needs replaced. I hate to buy 3 if I only need 1.

 

Does it send any codes(service engine soon light)? Its it running strong? When was the last tune up you did?

 

No codes. It seems to be running good and strong just the gas mileage sucks now. I was getting around 19-21 when I bought it and now its around 16. I cleaned the mass air flow sensor also just to check. It had a recent tune up right before I bought it at about 130K

 

Make sure your tires are properly inflated, underinflation can cause poor mileage. If you're not getting a Service Engine Soon(SES) light, don't go changin' the HO2S's just yet. AND DEFFINITELY don't change the injectors, If these are bad it will have MUCH worse problems than poor fuel economy (At the very least a missfire and SES light)