buymeavette

alright if it was the above mention: fuel filter, fuel pump, or regular vs syn oil used i am using my not GM technician knowledge (but what i know from whatever experience i have) but i can tell its known of these.

first off: at 50K change out the PVC, Fuel Filter, Plugs/Wire ( GAP PLUGS CORRECT!!!!!) air filter, rear end fluid, trans fluid and filter, get some freshness running through the car. maybe even a radiator flush.

anyways about your problem. big thing no one has said and i'm very suprised is the 02 sensor. they would normally cause a fuel mileage to dump like that. my friends 87 cutlass 02 went out, he was getting 13 MPG no matter how he drived. we fixed the 02 sensor and with him nice on the throttle he was back at 19MPG. nice increase.

but thats why i say its not the fuel pump, fuel filter, or oil. Fuel pump you would KNOW if it is going. Sounds would be made and/or it would be chugging along when you get on it, etc. If the man is towing a boat he seems to be getting some fuel to the motor to pull that and the truck with it. so to me, from what i've read... fuel isn't an issue. however air/fuel mixture can be an issue. which brings me back to 02 sensors. often over looked!

but fuel mileage can be affected by tire pressure, bad tires, poor spark, etc etc. think of all the ways in which fuel can just go through the exhaust valve with out being burned. many reasons! check your 02 sensors, see how it looks. if they look like a bad spark plug then your in business!!!! smell the exhaust too, to smell if it smells like an old muscle car.... emissions could be from it.

anyways... just my two cents.

Mort

It could be the fuel regulator. Pull the vacuum line off of it and if there is fuel in it then it is bad. How about the intake. Maybe the air filter is getting clogged up and needs to be changed or the intake track may be dirty. Take the tube off and check the throttle body and the MAF. If they look dirty then clean them up. The MAF can be cleaned with electronic contact cleaner and the TB can be cleaned with the same thing or carb cleaner. Just spray it on and wipe the gunk off inside and out. Do not touch the wires on the MAF as they are quite fragile.

SLOW 94 LT1

iTrader: (4)

!!! I forgot all about the O2 sensors. I bet that could be some of the problem. Soon enough it will be back to the way it should be. I tried to convince him to put headers on it, but for some godawful reason my Dad seems to think it will burn up the valves and such. He won't even put exhaust on it. Maybe one of these days I'll convince him.

900Z1

Run the tank almost to empty, put in some injector cleaner and fill up with 93
or 94 octane. It helped mine out.

shandy294

Unfortunately it has four 02 sensors and they are 60 bucks a piece. I think just the front ones are possible suspects for a mileage-drop problem but not sure. I wouldn't just 'shotgun' them because of their cost...try to verify their condition.

1FUNZ71

odometer could be off as well. If the trucks still runs as good. you could always scan the pcm.

maximumrebel1

You said he gets 17 no matter how he drives even towing a boat. 17 is damn good for pulling a boat. Yeah he should be getting better if he drives slow but 17 isn't to shabby. I have a 5.3 with 160,000 miles on it and get from 16-18. Hope you figure out the problem.

SLOW 94 LT1

iTrader: (4)

FOUR?! Where are they all located? 1 on each manifold and 1 after the cat I'm sure. Where is this fourth one? Don't tell me they got another one before the cat.

maximumrebel1

Isn't their 1 behind each cat?

bigguy75inches

there are to cats, one after each header, then they y together. 1 after each header, then 1 after each cat.