kyle450rider

I'm gettiing about 13.8mpg out of my 1994 toyota 4x4 truck with a 22r and 5 speed. THis is way worse than I was expecting from the vehicle. To give you a comparison my buddy has a 1986 four runner and he's averaging 21-25MPG's. What gives? My truck has 150k with no mods or hopups,bonestock. I am planning on getting a timing chain and valve adjustment soon. Could this be the problem. Someone mentioned an O2 sensor could be bad. How would this affect my MPG's? THanks for the help.

thook

The O2 sensor tells the ECM to adjust fuel ratio according to the presence of oxygen in the exhaust. It goes back and forth accordingly....more fuel/less fuel. If the sensor is bad, it can't read the mix nor send correct signals to the computer. Google can tell you more specifics.

If you're not throwing any CEL codes, the O2 sensor may be just fine. You can always test it.

Why the timing chain? When's the last time you had a tune up?....rotor, cap, plugs, wires, valve adjust, etc.? Have you checked the timing? Fuel filter? Is it running poorly? Related to engine temperature?

Allstar93088

A bad 02 sensor causes your motor to run to rich. The fuel to air ratio is thrown off from a bad 02 sensor...I replaced mine and gained about 3-4 mpg. Best bet would be to replace it if you suspect it to be bad, especially if it has never been replaced.

thook

Man, that is just throwing parts at it. It may not be the problem. Why do people like to do that?

Yodaforce

Wait a minute. Is it a 22r or 22re? Are you running stock size tires? Are you running around with a loaded tool box? There are alot of different variables that can influence gas mileage. Are you driving around town (stop and go)? Do you have a lead foot? I can get as much as 20mpg in my 87 with a Weber 36dgev, but I drive twistiy roads all day and tend to lay into the throttle alot, giving me more of a 15mpg average. Lets not just jump into expensive repairs until it can be determined that something is actually wrong.

dcg9381

The 02 sensor is a "very likely" candidate for this sort of problem.

If you don't want to throw parts at it - test the 02 sensor. The procedure is described in the FSM.

grayguy

My truck got 25mpg the first 2 weeks I had it, and then slowly dropped of to averaging 18mpg. Then I started delivering pizza in it again, and get about 14-16. The crappy mileage while delivering makes perfect sense, but the 25-18 drop doesn't because the only things that changed were new oil, and the Cat-back was removed (but is staryed 18mpg when reinstalled). I hope to get back up to 18mpg someday.

Dziuggy

well it might be driver related. ECU learns how you drive and changes fuel maps according to that. so if the previous owner was driving like a granny = better gas milleage, now if you start steping on itafter few weeks ECU will give more fuel to acomodate more spirited driving. and you can reset ECU by pulling EFI fuse and leaving it out for 20 seconds

cheers ziggy

thook

This is I did not know. It's a fact?

80W90

this ecu does not have adaptive memory threshold limits. it only has two limits, open loop and normal.

farmerj

best thing I did for my 88 22RE with 5 speed, drive by the tach.

I shift at or before 2000 rpm. I do anything I can to avoid going over that rpm.

My winter average is like 18 mpg and my summer is 22 mpg.

If I get on the interstate, I will be running around 2800-3000 rpm, my mileage will be around 17-18 mpg.

If I stay on state highway, I am around 2200-2500, I will get over 21 mpg.

I need to get rid of my 31-10.50R 15 tires and get back to the original 225/75R15 tires. I think this will be the biggest factor in getting my mileage higher. Either that, or change my final gear ration to what that would be with 4.11 gears and 225 tires.


I had serious power and mileage issues on my truck when we first got in in 2004. Every time I notice a big drop in expected mileage, I look at my plug wires first. For some reason, #4 tends to get more opens into it than the other 3 cylinders.

New cap and rotor made the next biggest change...

Someone had also decided to perform the "MAF sensor adjust". Talk about a nightmare getting this back to a decent setting. Took almost 7 months of "make and adjust, see what happens" before I got it right. This alone made the biggest change in power and mileage.

Just general putzing has made this truck a great daily driver. It starts reliably down to -20 degrees. The only time I have had an issue with the battery is when I left the lights on.

As to the O2 sensor. I finally changed it this fall when I put in a new exhaust system. Didn't make that big of a difference.

kyle450rider

I forgot to mention that its highway mileage running between 60-70mph. I have stock tires and the size is 225 70 15....I think. I know that its not the 31x10.5. I'm going to look into some stuff this weekend. I know the old owner ran it around town only and I've been driving to work on the highway. I hope to squeeze some more out of it. It I can't its back to driving the f150 that gets 17-19mpgs.

farmerj

Sounds like issues of a heavy extremity.