I need help figuring out why I'm getting such bad mpg. I usually fill completely up and reset my odo, then when it gets low I go to the same station and fill completely back up and use how every many gallons to calculate it. I keep coming up with close to 13.5 mpg.

I have a 95 blazer 2 door, 4.3 CPI, and automatic with 3.42 gears. It has 205 tires and is lowered 3 inches. I do usually run the a/c.
I have replaced:
spark plugs (ac delco)
wires
cap and rotor
fuel filter
cold air intake
tps sensor
idle control valve
egr valve
oxygen sensor
new cat

I did notice that my truck only has one oxygen sensor. Its before the cat right where the y pipe comes together.

I just don't understand why I would get this. I know the cpi are prone to leaks, but I did a pressure test and its holds at close to 60 all day. and theres no washing in the upper intake. I have also seafoamed it. Any help appreciated. Thanks!

 

Hmm ouch. I know a friend of mine has a 96,which gets about 14-15 mpg with ac off. But he has 4x4. Have you checked the timing by chance? Hows the air filter lookin? Also have you cleaned the throttle body recently? You got me stumped trying to think of ideas. and im usually pretty good at doing it. Maybe your fan clutch could be bad,not unlocking when its suppose to and causing drag on the engine.

 

I've got an electric fan on it so not the fan clutch.

do you know the procedure for checking the timing? I will deff check that

 

gas leak by any chance? i noticed the same numbers......crawled under the took to have a look, and noticed that my gas tank was wet...... and strong fuel smell....those plastic covers to "protect" the tank do an exellent job of collecting road salt and eating away at the tank.

 

Sure,mark the line on the crank pulley with some white out,or chalk so u can see it when its spinning better with the timing light.

Unplug the timing wire under the passenger side of the dash,up above where your feet would be,its a tiny tan/black wire. Then start the blazer. the engine light will come on which is normal.

Hook up the timing light to #1 plug wire which is the plug wire closest to the front of the engine,on drivers side. Look at the crank pulleywith the timing light,the mark should be on 0*. It might move around a tiny bit,which is ok. If its way off 0* turn the distributor until its on 0*. Cut the truck off,plug that wire back in and start it up. Whalla.

 

If your plug wires are not sticking out the top of the distributor cap, but the sides, you have to follow the EDI Engine Timing procedure as detailed in the Tech Article (DIY) post found in the index link below.

 

I just checked the timing and its dead on.

I will check the tank.

 

just put the rear up on ramps and no leaks at the tank. everything is dry under the truck.

i just dont know.

 

Engine down on power due to age/mileage? It's a possibility.

Sub-par fuel quality? Have you tried another station for a month or so to see if it has any impact?

 

Is the 13.5 highway or city?