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1999 chevy 2500 getting bad gas milage

twoslo4five0

twoslo4five0

3/4 ton status
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ok so ive been using my 2500 for a lil while now..i pretty much only use it for towing...ive been geeting 6 to 8 miles to the gallon all the time...here are some specs on the truck

1999 chevy 2500 crew,shortbed
5.7 vortec
3.73s
4l80e

ok here are some symptoms

hot start problem
lack of power
low idle
servise engine light on

i know it needs a tune up (gonna do it tomm) and it needs a air filter,ect but i was talking to some other people about 5.7 vortecs and they were getting 15 to 20 mpg not towing and some were getting around 12 towing..12 would be a HUGE improvment for me...i think the timing is off but i was reading you can use a timing light on a vortec motor :dunno:

also i have noticed that the truck does search between 3rd and 4th on the highway especially if the cruise is on...i guess theonly way to fix that is to regear...anyone with input on this stuff or similar experiances??
 
15 to 20?? i doubt you'll see the higher end of that. do the tuneup and see where that gets ya. do the fuel filter too. i bet it's missing, that why the light is on. how many miles are on it?
 
YZEATER said:
15 to 20?? i doubt you'll see the higher end of that. do the tuneup and see where that gets ya. do the fuel filter too. i bet it's missing, that why the light is on. how many miles are on it?
Click to expand...
x2!!!! i towed my trans am 400 mile home w my ol 99 vortec 5.7 old body style ext cab short box on a bad fuel filter!!!!! 35 mph up hills:mad::mad:
 
theres apparently a known problem with these vortecs (my '97 454 has the same sympotoms and code) base timing out of adjustment. and to get that I think there only 2 things that can be wrong, timing chain very loose, and the distributor drive gear worn. and from reading around the '96-'XX vortecs had a problem with soft metal on the dizzy drive gear wearing prematurely. I can't recall the code #........ maybe P0213....... but for sure its called base timing out of adjustment.
 
Sounds like one of those "all of the above" situations... My 1 ton has the vortec 454 and I couldn't imagine running a 5.7 as I feel the 454 is at the low end of the power spectrum for trucks of this size...
I get a consistent 10-11mpg in my rig and 8ish when towing (10k or so)...

Let us know what the tune-up and fuel filter do for ya'...
 
Avery4jc said:
Sounds like one of those "all of the above" situations... My 1 ton has the vortec 454 and I couldn't imagine running a 5.7 as I feel the 454 is at the low end of the power spectrum for trucks of this size...
I get a consistent 10-11mpg in my rig and 8ish when towing (10k or so)...

Let us know what the tune-up and fuel filter do for ya'...
Click to expand...
really the power is ok...not the greatest but way better than the old 5.7 i was using in my burb...i just want the gas mileage to get better
 
I got a '94 with 5.7 and 700 r4 and i get around 16-18mpg but i think i have 3:42's. IMO i'd check the fuel filter. They can definately ruin your mileage

I've heard the same thing with the timing on these. Definately post up after gettin the codes pulled
 
well the vortec blues. if tuneup is in order few must haves.

factory acdelco plugs = or skip/surges will happen.

prem cap/rotor = bad venting and tons of carbon tracking. some even send update sheet. says punch out the dist housing vent screen for more flow of air.

good wires = thay are cheep and you are there.

new coil if money will kick it. = if its firing all that time then swap it.

fuel filter is a big problem on these trucks = trap tons of dirt and can restric flow vary easy.

and setting timming requires a prem scanner like factory/snapon or otheers. there is a setup option to set timming . sorry thats all thats offered. but it will only kick a code if +/- 4* out from zero if i recall correctly.
 
did you do the tune up yet? plugs wires ect.

quick google search says crank position sensor.
 
i didnt want to do any of that and not fix that problem first just in case whatever was wrong fouled out all the plugs ect...i did a google serch as well but im seeing all diffrent things like adjust timing,the cam sensor,dist cap,worn out dist gear...i dont know where 2 begin
 
i work on this stuff all day. read my post and basicly do it. if you dont know if or when it was all done before then more importent.
 
Do a tune up dude, these trucks are ultra sensative to everything sweetk30 said. Fuel filters are a must on these trucks every few thousand miles.

Start simple
 
Last edited:
sweetk30 said:
i work on this stuff all day. read my post and basicly do it. if you dont know if or when it was all done before then more importent.
Click to expand...
ok updates tomm hopefully...any advise on wires/cap ect..i have a 50 dollar gift card to pep boys so im prolly going there
 
All i can add is use NGK V-power plugs, i've been running them for years with excellent results. Also use the good cap with the brass terminals.
 
ight so i got plugs,wires,cap,rotor,air filter and a fuel filter for the amazing low price of 130 bucks :screwy: holy crap i forgot this newer stuff is more expensive to work on..going to start putting it all on in a few
 
did a tune up...it needed it badly...i dont think in 160k it had ever been done...definite diffrence in power...we tried to clear the light the old fassion way (unpluging the battery and touching the cables together,no airbag dont worry) but it didnt work...hopefully i will see a diffrence in gas milage now

some pics i took

001-28.jpg


i should have taken a pic beside the new filter total diffrence
002-23.jpg


the plugs were bad
003-18.jpg


the cap was corroded too
004-14.jpg
 
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