Terrible gas mileage

[kinjo1977]

Ran a couple tanks through my truck and averaged 15 mpg.............As you can see from my sig, I haven't done any mods that would cause such a big drop in gas mileage. I checked for leaks but there are none. Could a fuel pump going bad cause this??

[rckrzy1]

Originally posted by kinjo1977@Aug 12 2004, 07:33 AM
Ran a couple tanks through my truck and averaged 15 mpg.............As you can see from my sig, I haven't done any mods that would cause such a big drop in gas mileage. I checked for leaks but there are none. Could a fuel pump going bad cause this??

Fuel pumps SUPPLY fuel not use it. Are you talking hwy mpg? Any codes?
How many miles? Plugged cat?

[kinjo1977]

Originally posted by rckrzy1@Aug 12 2004, 08:17 AM
Fuel pumps SUPPLY fuel not use it. Are you talking hwy mpg? Any codes?
How many miles? Plugged cat?

I'm talking normal everyday driving. No extreme race driving or anything like that.
Ran a diagnostic but didn't pull up any codes. Said "ok to drive".
Never had anything in my truck except Premium 93octane. I run Lucas fuel additive through my fuel every 3 tanks and I have 66K on my truck.

I dunno if its a plugged cat....could be. I have been wanting to replace my current exhaust setup but haven't gotten around to it yet. When I do the cats will definately be replaced.

[rckrzy1]

do you know what your fuel trims are? Might be a bad FPR (fuel
pressure regulator).

[8budfan]

with the 4.8 and std tire size..you should be gettin 17 to 21 mpg.more stop and go driving will cause you to be below those #'s but not much only 1 or 2 mpg less..

[kinjo1977]

Originally posted by rckrzy1@Aug 12 2004, 10:06 AM
do you know what your fuel trims are? Might be a bad FPR (fuel
pressure regulator).

Don't know....but if it was a bad fpr wouldn't it show up when I did the diagnostic?

[rckrzy1]

Originally posted by kinjo1977+Aug 12 2004, 12:44 PM--><div class='quotetop'>QUOTE(kinjo1977 &#064; Aug 12 2004, 12:44 PM)</div>

<!--QuoteBegin-rckrzy1

@Aug 12 2004, 10:06 AM
do you know what your fuel trims are? Might be a bad FPR (fuel
pressure regulator).

Don&#39;t know....but if it was a bad fpr wouldn&#39;t it show up when I did the diagnostic? [/b]

I don&#39;t think anything monitors fuel input to the injectors, but I could
be wrong, I am more knowledable on the LT-1s. But if the FPR
is blown and you are getting full pressure on the injectors you should
have some black exhaust, rich as can be.

[kinjo1977]

Nope....exhaust isn&#39;t black. I did get under my truck and examine my exhaust system. Noticed that I had alot of black carbon build-up around the connection of my y-pipe and the pipe that goes into my muffler. Looks like it could be a minor exhaust leak...but I don&#39;t believe that would cause poor gas mileage.

[Hit Man X]

Have you changed the fuel filter lately?

What about a general tune up in general?

[kinjo1977]

Changed the fuel filter exactly 9,000 miles ago. Haven&#39;t had a tune up....figured I shouldn&#39;t need one at only 66k.