Need help improving gas mileage

[rharmon]

I have a '93 s-10 blazer, 4.3 liter vortec engine.

I've replaced the fuel pump, fuel screen, fuel filter, fuel injector assembly, fuel lines, spark plugs, PCM. I have a K&N air filter. The oil and oil filter is changed every 3000 miles. I get between 10-11 MPG in town driving. This is bad. Any suggestions on how to improve this? I think the 02 sensor is ok. I've read that replacing the exhaust system can help. Would it do any good to replace everything from the catalytic cvtr back(pipe, muffler and tailpipe)?

[Ezee5]

Originally Posted by rharmon

I have a '93 s-10 blazer, 4.3 liter vortec engine.

I've replaced the fuel pump, fuel screen, fuel filter, fuel injector assembly, fuel lines, spark plugs, PCM. I have a K&N air filter. The oil and oil filter is changed every 3000 miles. I get between 10-11 MPG in town driving. This is bad. Any suggestions on how to improve this? I think the 02 sensor is ok. I've read that replacing the exhaust system can help. Would it do any good to replace everything from the catalytic cvtr back(pipe, muffler and tailpipe)?

Check the sidewall print on your tires and see what is suggested for actual tire pressure. You might be surprised.... (and maybe not ! ) at what it says.

[rharmon]

I recalculated my mileage. It's just over 12 mpg. Tire pressure is good. Any other ideas?

[pernicev]

The tire pressure should be what is marked on the inside of the driver door, unless that psi number exceeds the pressure marked on the tire's sidewall. If that is the case, go with the pressure marked on the sidewall.
Have you changed the other fluids such as differential and transmission? Those probably wouldn't make much of a difference anyway. Replacing the exhaust shouldn't make a difference either, since a more free flowing exhaust would cause better mileage, but a faulty catalytic converter might. I would check your O2 sensors (search my past posts on how to do this), there are a few sensors. If they check out and you car has a lot of miles on it (like more than 130K), it might be your cat. If the cat is bad, the O2 sensor after the cat sends a message to the computer to increase the mixture which could result in lower mileage.
Other than that, take a look at how your driving. Do you floor the pedal frequently? Do you carry a lot of cargo? How you drive could affect it too. A K&N filter, since it's less restrictive, could be causing you to drive faster/more aggressive than you think. Anyway, remember that the Blazer is HEAVY and driving around town mileage probably wont' be better than around high teens give or take.

[mjohn]

At 10-12 MPG...and if this is a Wseries...

Then the internal fuel lines are leaking, fuel pressure regulator...leaking...or CPI is shot...

Search this thread for these items and enjoy the reading...the down side of the Vortec 4.3

[criticalbass]

My '86 4.3 (It's a carbureted vortec!) sits in a 1/2 ton full sized Chevy pickup, and it gets 14 around town and 17 on the road. Something is very wrong to cause the poor mileage you are experiencing. Don't spend money on fuel saving devices right now. Diagnose and fix what's wrong, and if you have to pay a mechanic, do it before whatever is wrong does damage to something else. (too much fuel eats muffler systems, converters, sensors, etc., not to mention dollar bills) CB

[rharmon]

Forgive my lack of knowledge about cars, but what do you mean by the internal fuel lines? If they are the 2 fuel lines that are leading into the fuel injector, I've had those replaced. Also the CPI has maybe 200 miles on it. It's brand new too. Fuel pump has also been replaced. Where exactly is the fuel pressure regulator? It is the '93 s-10 blazer "W" code. I know I can buy this part from advance autoparts for about $25. Maybe I'll just replace that.

Also, how much difference does the fuel filter really make? I had it replaced about 400 miles ago but is it possible it could be clogged or something?

[Rowlin]

usualy u change the fuel filter every time u do a tune up
when u changed the plugs and stuff did u look after the pcv and when was the last time u cleaned the K&N. Another thing that would help the truck is a moto vac, its a cleaner that they run through the furl line and injectors that cleans out carbon deposits it also cleans out carbon that is inside tha cylinders and valves

[rharmon]

PCV and K&N are both new. Do you just take it to the dealership for that moto vac?

[Rowlin]

u could but smaller shop usually have it for a better price the moto vace will make the truck rum better