low fuel mileage
Thread Starter
8th Gear
Joined: Jun 2002
Posts: 8
Likes: 0
From: San Diego ca
low fuel mileage
I am at my limit and need help. 85 with rebuilt motor automatic new items: injectors, fuel pump, egr valve and solinoid, tune up, air filter, catalytic convertor. No codes runs well but only gets 13.5 miles per gallon (calculated). No gas smell no hard start passes smog with ease. It is not driven hard(my daughters car), mostly city some highway. Has anybody got any Idea what could be wrong with the car?
Thanks
Thanks
Drifting
Joined: Feb 2000
Posts: 1,994
Likes: 0
From: Charleston, WV
Re: low fuel mileage (dra85)
Did it suddenly drop to that level or was it always that way? ........That's not really out of line for around town.............. but if it suddenly dropped ......... that's different...... what's the timing set at?......... was it set correctly?......... hey is the balancer ok?........ could cause it to give an incorrect timing reading............ :seeya
Racer
Joined: Aug 2002
Posts: 253
Likes: 0
From: Strongsville Ohio
Re: low fuel mileage (dra85)
You'll need to scan the car, I wouldn't be surprised if the engine is staying in open loop, I would be suspicious of the O2 sensor if this is the case. Open loop is full rich full advance. It can have a significant effect on fuel mileage
Thread Starter
8th Gear
Joined: Jun 2002
Posts: 8
Likes: 0
From: San Diego ca
Re: low fuel mileage (vettmech)
Its been that way since Ive owned the car, I bought it knowing that it needed to bee rebuilt. New dampner also, timing correct. I don't have a scanner but I ran it in the diagnostic mode and the ses light was flashing about once every second after it came up to temp. New o2 sensor also.
[Modified by dra85, 9:02 PM 10/15/2002]
[Modified by dra85, 9:02 PM 10/15/2002]
Team Owner
Joined: Apr 2002
Posts: 43,370
Likes: 0
Re: low fuel mileage (Stingray1970)
You'll need to scan the car, I wouldn't be surprised if the engine is staying in open loop, I would be suspicious of the O2 sensor if this is the case. Open loop is full rich full advance. It can have a significant effect on fuel mileage
Team Owner
Joined: Sep 2001
Posts: 62,143
Likes: 1,730
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Re: low fuel mileage (GDP)
I believe that if any of the O2 sensors is even starting to give out they'll throw a code at you. Is this wrong?
If youre gettin terrible mileage, it would be the o2 sensor/fuel pump/filter/injectors most of the time. Of course it could be something with the ECM too, but i doubt it.
Or you have to much lead in your foot.
Burning Brakes
Joined: Feb 2000
Posts: 824
Likes: 2
From: Camden SC
Re: low fuel mileage (vader86)
I'm with the O2 sensor group. As stated above, a good scanner will help determine if your car is going to closed loop and monitor the 02 sensor voltage. Even at idle, the voltage should jump around. It could be sensing lean and then pulsing the injectors longer than necessary. If you cannot locate a good scannner, there are some tests that can be done with a sensor removed, good volt-ohmeter. I seldom recommend just throwing on parts as a trouble shooting technique but with an O2 sensor, a new one never hurts. They can become quite "lazy", hang at the wrong voltage, and never throw a code. Believe the factory service manual has a trouble shooting chart for low mileage. Have you checked this?
Oh yea, not related but unless you know the service history of the fuel filter, replace it. Partially clogged fuel filters are suspected by some to be the leading cause for premature fuel pump failure. With a new pump, best to install a new filter and then you know where your at. Just my opinion.
Darn cars, always something.
dlmeyers 90 coupe zf6 3 speed shocks
[Modified by dlmeyers, 3:29 PM 10/16/2002]
Oh yea, not related but unless you know the service history of the fuel filter, replace it. Partially clogged fuel filters are suspected by some to be the leading cause for premature fuel pump failure. With a new pump, best to install a new filter and then you know where your at. Just my opinion.
Darn cars, always something.
dlmeyers 90 coupe zf6 3 speed shocks
[Modified by dlmeyers, 3:29 PM 10/16/2002]
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Joined: May 2002
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Re: low fuel mileage (dra85)
Wouldn't a bad O2 sensor show up on a smog inspection?..cause the car to run too rich?
I get pretty bad gas mileage in town, but then again, every town is different. We spend lots of time idling at stoplights here (0 mpg).
I get pretty bad gas mileage in town, but then again, every town is different. We spend lots of time idling at stoplights here (0 mpg).