Bod MPG

[JoeHill]

right now I am getting 10 city and 12 highway. it should be getting about 17 and 20. I dont have any idea why. the engine is very smooth, the RPM dont run high. no indicator lights are on. its an AT that is shifting fine(just had the fluid flushed.) I would say i am taking it easy on the gas peddle.l i think the tires are 31 inches.
an example: i just drove it des moines from MPLS this weekend. its about 240 mile drive and I couldnt make it on one tank.

I do need to get it fixed with gas prices being what they are.

What could it be?

 

[WaterMan]

Try checking the codes from your OBD2 port. (Some local auto parts stores will do it for free.) See if you have a pending code, especially for your O2 sensors.
As old as your 4R is, it could be they are going bad. Bad sensors will run a richer mixture...and therefore burning more fuel.

 

[JP4RNR]

Try checking the codes from your OBD2 port. (Some local auto parts stores will do it for free.) See if you have a pending code, especially for your O2 sensors.
As old as your 4R is, it could be they are going bad. Bad sensors will run a richer mixture...and therefore burning more fuel.

1990 is Pre-OBD II. OBD II did not come out untill 1996. You have to short terminals T and E1 and watch the number of times the Check engine light flashes. The number of flashes indicates the code. Five flashes is code number 5

 

[wolfgang]

The MPG rating back then was only 14-16 MPG for automatic w/ stock 225/75x15 tires. The 5 spd did 15-18 MPG. I had a '90 22RE w/5spd that got 17-22. I've read that the AT was the problem and that in '95 or '96 they changed the torque converter lock up to give better mileage. Have you tried comparing the speedo miles driven to a GPS to see if your odometer is off from the larger size tires? Add 3-4# over comfort tire pressure for better mileage and clean out the junk in the back. Injectors might need cleaning and recalibrating too --- may leak a bit when not in use or one or two spray too much. Try a K&N air filter too. Recall some folks swapping out the 3L engine for a GM 3.8 or 4.3L and getting far better than stock gas mileage. It just wasn't a powerful or economic engine!