I would check vacuum lines, especially to storage tank in left fender. You might consider injector cleaner or seafoam.
I assume you are running gas, and not E85. Are the plugs AC Delco? if not, I would replace them. What speed is your highway driving. My 2002 will get about 25 @55 mph. I haven't really had it on a trip @ interstate speeds.

 

Ill try some injector cleaner, I havent checked the type of plugs, i set my cruise at 70mph, and yes im running gas...by left fender you mean DS front or PS front....thanks for the help!!!

 

Sorry, driver's side.
Injector cleaner cleaner or seafoam will also clean o2 sensors.

 

so let me see if i got this right... for the best results of Inj cleaner, i should run the truck to 1/4 tank then add it, drive to empty, then fill up right?

 

there's a vac tee in the left corner firewall area,the one going towards fender does dry out as i had to replace mine yesterday.i have a vac guage so you can see it drop.did you save the old sparkplugs if so you can use them to cleanout the inj system by adding a1/3 can of seafoam to the vac line from p/brake booster while motor is running and shut off for 1 hr.restart let the smoke clear after about 5mile drive and you'll be good to go there.reinstall the good plugs cuz that cleaner will prolly foul them out.if you use a live data scanner look to see how o2 sensor is fluctuating,a range of .02--.09 and very fast if slow or stuck at .45 the sensor is ng.

 

what kind of plug's got put in it ?....shitty plug's = bad mpg

 

well ill have to pull a plug to find out...or check the repair log the guy i bought my truck off of....that would be a little easier

 

I also just replaced that hose in the drivers side fender, completely fell apart as soon as I touched it. I had noticed my mileage was down a little, hopefully that was the cause.

 

Well all good info....im at work right now but as soon as i can get to my truck ill check it out...... im hoping its just a vac line, that would be GREAT!! Are there any other dead give-aways to this?? My mileage is definatly crap, just yesturday i went through a 1/4 tank on a round trip to work, and i think my throw out bearin is leavin me too, i hear somethin chattering if i let the clutch out in neutral, everyone i know that has the same truck says its very common

 

Go to Advance Auto or another big box retailer and ask them to scan the computer. These stores stock a Actron or whatever scanner to check for codes for free. O2 sensors are common culprits. Check your plug wires and distributor cap/rotor button if your model has one.

 

Well i checked my vacuum line the one with the T.. no dry rot or anything, ill get a vacuum test done though...not too sure what else to do but get another set of plugs and run sea foam

 

live scan for 02 sensor readings

 

Hey guys. I live in Ocala Fla and have the same problem. Mine's a 2000 2.2 ,ext cab, autotrans and A/C.Bought it with 74000k and a cracked block(former owner didn't believe in oil changes and ignored check engine light).Dropped in a new(not reman) engine from Chevy Oct 2011.Got great mileage until 12 weeks ago.No codes.It runs great with strong vaccuum at idle.I have found out the oil refiners at the ''request'' of the ''gubment'' have increased their ethanol content.Blame the tree huggers!Read the 2006 Consumer reports article ''The ethanol myth''.It will explain a lot! I went from 19-21 city-22-25 highway to 17.5 city-21-23.5 highway.You are right though,14 mpg is way low.I hope this helps.----God bless---Shep P.S---THANK YOU SO MUCH FOR YOUR SERVICE!

 

Are you going off the gas gauge and tank capacity to calculate mileage? If so that's wrong. Reset your trip odometer when you fill it, record the mileage the next time you fill up, and divide the number of miles by the number of gallons it took to refill it.

Other info: is your truck a Flex Fuel? Stick or automatic?