Terrible Milage. 5km/liter 350tbi.
 

Hey, I am new here and I am getting 5km per liter. which i dont know what that is in mpg. But it isnt good! I am sick of dumping gas into this pig.

I bought it back in january, told it had a new motor and tranny 10 000kms ago. didnt notice till after i bought it that it drank gas, and had no power. So i got the timing changed. It was at like 8 degrees out i think. But know its back at 0 i think. The truck had a bad bog as soon as it warmed up. So i changed the TPS and ECTS. Nothing. So brought it to a shop, and they unplugged the EGR. They said i need a new one. But the mechanic has the same truck and said he bypassed it. that fixed the bog, but its no better on gas. I cut off the cat, and gained alot of power, but no mileage gain. We changed the distributer and wires. and rotor and cap and what not, fuel filter and air filter.

It throws no codes. I assume the new motor is a 350. I dont know what else to check. Im just getting into trucks, and dont know much about this sort of stuff.

I ran 1 container of injector cleaner threw it, but nothing, that was a while back however. I still think it may be injectors because. If i leave the truck for a few hours. it takes a few cranks for it to start. but if its only off for a few minutes. it will fire back up instantly. Could it be slowly flooding itself? threw another can of cleaner in it and nothing..

Thanks, Mark

5km/L equates to 11.67MPG, which is bad, but it's not ridiculously horrible. As for fixing it and your issues, I have absolutely no idea; I hope somebody can help you soon brother.

It may be on the outside
 

How is your truck equipped on the outside? Lights mirrors, covers? Do you pull trailers?
I get 6,7 km/liter at best from my -89 350 tbi. When I pull a big trailer I only get 3,3 km /liter.
Its not he heavy load that does it. I have found that it is mostly the drag the air is forcing on the team that hurts the most. Or more correctly, the drag makes me use more force (use more fuel) to cut thru the air.
This is when i pull a big covered trailer, almost regardless of weight. But when i pull a heavier miniexcavator I'm doing better than 4km/liter.
It's also about how I drive. Aggressive driving, flooring the pedal, slamming the brakes ruins the mileage. Small 1.4 liter Civics and such are not so sensitive to this kind of treatment. But these heavy trucks with big V8's are.

what ratio differential do you have?

if you bought the truck used and it has modifications such as new motor, transmission, it could have a very low ratio differential, say a 4.56 or 4.88

I think you can check it by jacking up the differential and turning the drive shaft.
get a close idea of the ratio.

new plugs, tuneup, check for a dragging rear brake,

i have a 350 with 3.73 ratio differential, it gets maybe 14 mpg at 55mph
10 mpg when towing about 6500#.

good luck with it.

I am getting 15.657mpg with the same setup as yours. U cancheck your gear ratio by driving at 55mph and looking to see how fast u are revving

You should check front wheel bearings as they will cut milage as well.On my dmax I pick up about 1mpg by repacking.

Thats 20 liter per 100 km. Thats pretty average really. You might be able to down it to 16 or seventeen, but that would depend more on your driving style then on the car itself.
I have a funny question though. Actually its 3 questions. Just to rule out all possibilities.

1) I take it this car has automatic transmission. Have you ever driven that before?
2) if it IS automatic transmission, do you know what the 2 different D's are for?
3) what country are you from?

This may seem a stupid question to you (and probably to all American car owners here,) but where I'm from, there are a lot of people who dont know what the second D is for on automatic transmission. Hence my question. Hope i dont offend anyone with it.

Do you have a lift and bigger tires? If so whats the gear ratio?

I have a 3" body lift, and a tiny bit bigger tires that stock. but my mileage was the same before i did the mods. I usually drive in overdrive. because thats what my manual said to use for everyday driving, and to save money. but i've been told by others to use regual drive, not sure. I do get heavy on the throttle often, and slam on the brakes hard. on the highway i have real troubles passing people though. the truck doesnt like 110+km/h

Overdrive is perfect. The other one is just for when pulling heavy loads or going somewhere very steep. But even then , most trucks have little or no problem with that.

Your way of driving will indeed get you to 20 liters per 100 km easily. Allthough your car should be able to go faster then 110 per hour. Mine does 130 and even then still accelerates at a steady pace. (130 is the max on my readers. But i guess it goes 160 or even 180.)

This is what my Van (pretty much the same engine and weight) does with a normal engine (running on liquid petrol gas because in belgium, normal fuel is just way too expensive).

0 to 100 in 12 seconds.
100 to 130 in another 12 seconds.

And please... dont drive and try to time it for yourself ;)

Do you actually hear the overdrive get to work when stamping down the pedal?
(My girlfriend calls it "letting all hell loose" ). If not then it might just be that your overdrive doesnt even work. And that would indeed explain the bad driving conditions. (vacuum hose or something that is malfunctioning).
But start with the timing test first. Have fun :D