Where did my fuel economy go??

[lowriderbowtie]

My 2.8 has been a dog on fuel in the last few months. It never used to be great, but it wasnt too bad. Im only getting about 350 km's on 40 liters or so (or 217 miles on 10.57 gal)
whats the deal? Anything i can do to my carb or what? I dont know where to begin. tune up? carb rebuild? help me out here

[Physh1]

Tune up, fuel filter change, and air cleaner would be first on my list. Reading the plugs will tell you alot about how the carb is running. Looks like you're getting 20mpg...what were you getting?

Cameron

[OBI WAN]

02 sensors should be added to the list of tuneup parts. 80-100K is about the best you can ask for a set to be top minded for tune and fuel economy.
Also how is the power, I suspect and very old cat!!

[lowriderbowtie]

Well before i was getting a good solid 500-600 kms on 40 liters.

Power seems good (for a 2.8) it will pull the speed limit up hills

and the cat is gone..just a big chunk of strait pipe into a dynomax muffler

My truck only has 115,000 kms on it

[T Man]

02 sensors should be added to the list of tuneup parts. 80-100K is about the best you can ask for a set to be top minded for tune and fuel economy.
Also how is the power, I suspect and very old cat!!


Unless it is a california truck it wont have o2 sensors. (Its an 85, no fuelie until 87.) You are getting 20+mpg? Im knocking down 17 on the highway. As far as options go, you could throw a new carb on there, I believe weber builds a great Carb for the 2.8 that doesnt have any problem dumping a TON of fuel. The first place I would look is your airfilter. If ignored, they will drop your fuel economy greatly. Fuel Filter is also a common problem linked to a drop in fuel economy. So, check your airfilter, replace it if it isnt new, they are cheep.

[OBI WAN]

I had 02 sensors on my 82 and also a 81 Trans Am!

[T Man]

Im tellin you though, on an S-Series, unless it is a cali, and maybe an Ny (but i dont think so) truck they didnt go computer controlled ill 87. I forgot to tell you lowrider, check your timing, thats a big one to kill mileage

[OBI WAN]

Maybe so, in 1981 on allmost all GM vehicles, we had 1 02 sensor minimum and obd1's.

[Sparky2263]

I think the vacuum advance may be inop. That would drop mileage about 2-3 mpg without any decrease in power. See if it's getting any vacuum and then see if it's actually advancing timing with vacuum applied.

No feedback carbs. on carbed S-10's unless CA.

[lowriderbowtie]

Update: I took my truck for a bit of a rip, put a few KM's on it....figured it out that i am getting 23 mpg on the highway, and 20 in the city. Aparently everyone with one of these engines, tells me thats pretty acceptable gas milage for these trucks. I guess i cant complain! o well...i always thought it was better

[blazen]

damn thats pretty good. or do you mean kpg not mpg. cause i get 18mph on the high way (on a good day at 65mph) and i was getting 13 mpg in the city. but i got the 4.3 and i have a lead foot.

[lowriderbowtie]

i converted it into U.S MPG

[blazen]

i converted it into U.S MPG

good thinkin cause us americans are stupid when it comes to forign stuff like that.

[lowriderbowtie]

hahaha