poor gas mileage

[1BadBowTie]

hello again,i recently noticed on my 92 with a basic 350 that runs really good for having nearly 170000 miles and a recent tune up is getting extremly poor gas mileage, last time i filled up i got 10.8 MPG??! I know its not gonna get 20, but i was hopin for maybe 13/14. my driving habits are pretty normal, tho it is mostly city driving, still should it be this bad?

[Blue Bowtie]

It's probably going to seem like I have more questions than answers, but I'll risk it anyway:

1. What fuel system (carb, TBI)?
2. What gearing on the truck?
3. What was involved in the recent tune-up?
4. Automatic or manual trans?
5. Does teh "city driving" ever include extended periods at 45MPH or higher?

Knowing some of those might help to determine if the mileage is abnormal or not.

[horse482]

Also to add to Blue's questions have you been letting it Idle a litte longer in the mornings lately?

[glenncof]

BadBowTie,

Do you have accurate MPG records before tune-up ?

Did you do the tune-up or someone else ?

[jocat54]

I have a 93 k1500 with 350 engine (3:73 gears) and have 197000 miles on it and have always got 17 to 18 on the highway except when the EGR went bad and it dropped to 11mpg, it did not set any codes when it went bad. Just a thought.

[1BadBowTie]

well to answer blues questions, its the TBI motor, the gearing i believe it 3:73 with limited slip...does anyone happen to know the code for the gearing to be sure?? i know G80 is limeted slip.. but to continue with answering questions, the tune-up was plugs ,wires,and rotor and it is an automatic, and yea, city driving does include goin 45/55 for a few miles, i take the back roads where ever i go, but even with the cold weather i havent let it sit outside to warm up, usualy its get in and go... so im pretty baffled?? i keep getting pretty much the same MPG everytime i fill up

[horse482]

Cats could be pluging up. What brand of tune up parts did you use?

[glenncof]

I would first check for any loose hoses, especially vacuum advance if so equiped. I don't know about a '92 but timing may be adjustable and not set properly.

Is there a reason you did not replace the dist cap (just curious)?

[1BadBowTie]

well i dont think its the cats, cause they have been long gone for a while, but the brand of part i used was carquest, as for the cap, i did replace that too, but i suppose it could be the timing, if i can change it, cause when its cold, it has a very slight sputter to it, guess im not sure if thats related