Bad Mpg!

Ok 91 silverado, been getting 9mpg not matter how I drive it. Well decided that is unacceptable so I did a full tune up. Everything, and what I found intresting is when I went to put the new pcv valve in, the old one was not pushed into the manifold it was just hanging there doing nothing. Another thing I noticed was that my 4x4 has been very slow to engage, I have to shift into reverse/neutrual/drive a few times for it to kick in. Well now with the new pcv valve correctly installed the 4x4 is working flawlesly again. Now I hope to see that my mpg is normal again. What is normal for the 350 throttle body? Let me know what you boys think.

paxfam1

I have a 93 5.7 4x4 and has always got 17 to 18 mpg on highway--13 to 15 in town all depending on how it is driven.
Not sure if the pcv really has anything to do with the 4x4 engaging.

I have a 93 5.7 4x4 and has always got 17 to 18 mpg on highway--13 to 15 in town all depending on how it is driven.
Not sure if the pcv really has anything to do with the 4x4 engaging.

Well I am sure it doesnt have anything to do with the 4x4 enageing but, it was essentialy a vacume leak cause it was just suck air. There for front end was enageing slow cause it was takeing awhile to build up enough vacume.

What else could be wrong I have done a full tune up and still I am getting about 9 miles to the gallon. Yes its mostly city driving but 9 is shit. What should I do.

So far:
Plugs
wires
dist cap/rotor
fuel filter
air cleaner
throttle body cleaned with the spray in can shit


What else could it be?

One thing I would be checking is the ECT. That bad boy should be running at least 90 degs. At the min. If it's not it will run real rich. You should have a scanner on it to see what it it running at.I would start with a stat and then head into the electric.

What else could be wrong I have done a full tune up and still I am getting about 9 miles to the gallon. Yes its mostly city driving but 9 is shit. What should I do.

So far:
Plugs
wires
dist cap/rotor
fuel filter
air cleaner
throttle body cleaned with the spray in can shit


What else could it be?
Hello All, My first post.

I have a 94 Silverado 4x4 5.7L.
It is currently getting 9 MPG in town, out of town, pulling the boat, not pulling the boat etc etc.

So Far New:

Distributor
Dist Cap/rotor
Plug Wires/coil wire
TPS (this helped a shift issue, but not mileage)
Temp Sensor
PVC Valve
Assorted vacuum lines
Throttle body cleaned
air filter
fuel filter

The engine seems to lose power at higher RPM.
The truck also hesitates alot when accelerating.

One clue I over looked.
When I start the truck the exhaust has a "rattle" to it.
Went and talked to an exhaust guy and he says to replace the
cat and my problems should go away.
He thinks the internals to the cat have rusted and are causing a
blockage with the exhaust.

Have not replaced it yet, but will be in the next couple weeks.

Long story short, don't over look your exhaust system.

Don J

One thing I would be checking is the ECT. That bad boy should be running at least 90 degs. At the min. If it's not it will run real rich. You should have a scanner on it to see what it it running at.I would start with a stat and then head into the electric.

Whats the ECT and How do I test the ECT and how would I got about adjusting it?

Whats the ECT and How do I test the ECT and how would I got about adjusting it?

Any other thoughts, motor sounds awesome and has plenty of power, just that 9mpg.