Im getting really really bad fuel milage

[grandprixgtp_91]

well im geting really poor fuel mileage. i fill the tank in my automatic GTP and i only get 400 km's to a tank and i drive it really easy. i put newer injectors in it, replaced all the filters and even replaced the fuel rail and regulator assembly. it doesnt even have 8,000 km on the new engine and i replaced all the sensors when i put the new engine in. i cannot afford to drive this car anmore with the price of gas, i am not getting any ses codes and the car seems to run perfect. what could be wrong because i drive the car every day and it costs over $60 a week. any help would be greatly appreciated. thanks

Jake

[PlatinumZ34]

Alright, my 1991 5 spd Z34 is doing the exact same thing, im getting in the range of 350-400km's to a tank, easy driving. I was actually just about to post about this, so thanks grandprixGTP, i haven't changed any sensors. Are there any vaccuum lines that would cause mileage to suck... cause im sure there are like at least 8 or 9 vaccuum lines broken off somewhere that i can't see.

I was revving the engine in the garage to hear the new mufflers and to see if i needed a resonator, and it came out blacker than i've ever seen an exhaust come out black, and there were flames (yes i have a cat, but its probably worn out)... So if anyone knows how to fix this, let us know

[Lyle's GTP]

Is this all city driving you speak of?

Lyle

[grandprixgtp_91]

no this is not all city driving, its 70% highway. and i know its not my vaccuum lines becuse i went out and bought a brand new vaccuum harness and i know they are all hooked up. i really need to figure this thing out the car used to get over 600km to a tank with the exact same driving conditions. thanks for any help you can give me.

Jake

[PlatinumZ34]

mines 100% city driving... (400kms = 250miles)

[dykz34]

Did you replace your o2 sensor when you put the new engine in?

[grandprixgtp_91]

yep

[93Oldsdroptop]

Do you guys run that re-formulated oxygenated gasoline up in Canada starting in the fall? I know that when we start running it down here in PA my mileage gets somewhat worse. I hate the shit.

[grandprixgtp_91]

not that i know of, and i know its not the new engine because it slowly got worse fuel milage before i put in the new engine.

Jake

[TheProfessor]

is your knock sensor ok
my girl was getting shitty mileage in her 90 prix cause the computer was retarding the timing cause of the knock sensor but you would be getting a code if that were the case

[grandprixgtp_91]

no i didnt replace the knock sensor because it was to expensive and i never got a light but all the other sensors were replaced, crank sensor, tps, iac, crap like that.

Jake

[97montez34]

i only get 250mi out of a tank full of gas... what about fuel filter and plug gaps?

[TheProfessor]

those are definate possibilities
how long since you have replaced that stuff

[grandprixgtp_91]

fuel filter was last year, and plugs were replaced and gapped a few months ago and only have 10,000 km roughly on them

Jake

[TheProfessor]

what kind of plugs