Absolutely terrible gas mileage

[justin_geb]

I have a 1995 4runner 3.slow. I put a generic air intake on it a while ago in hopes of maybe getting a little better mileage and horsepower, not to mention the mean sound it gives it. And for a while it seemed to make a little difference. But then my check engine light came on. When the light comes on, it drags really bad. Like I can barely go 55 over a hill with it mashed to the floor. The mileage goes to complete crap. I had to drive it this week to get to school and drove maybe 150 miles and went through 3/4 of a tank. I have had some people tell me it could be the catalytic converter plugged up, which I agree, it could be plugged up. But what caused it to plug in the first lace is what concerns me. So before I get a chance to pull the codes in a couple weeks (I'm not going to be driving it until then) any one have any ideas? Would replacing the catalytic converter solve the problem or would it just clog again?

 

[giro]

There's a good chance that it's a bad O2 sensor. With that mucked up, the computer sends the wrong amount of gas for a good fuel/air ratio, you get less power, and get less mpg. Any chance it's also smoking out the tailpipe?

Really it could be another sensor instead. But the O2 is most likely.

The cat is past everything….in this 4runner you don't have a 2nd o2 sensor after the cat. So aside from the cat being really plugged so much that it mucks with the airflow, it shouldn't matter. If you cat it a bolt on one (mine was in a 92, but I think they stopped), you can even test this theory by disconnecting it. This will make the truck really load, and have worse emissions, but to just test out a theory it can be done.

The problem is if the ECU is sending the wrong fuel mixture, it can foul the cat. I don't know how long that takes, but if you know it's sending the wrong mixture you shouldn't drive it too much. Another option is disconnecting the MAF (or the O2). If a sensor is bad (hence the CEL) this will cause the ECU to use the default mixture instead of a mixture based off bad data. The FSM says there's a "limp home" mode, so unplugging a sensor is likely the same or similar thing, but it could be good to try if needed.

Getting the code for that CEL is as easy as using a wire to connect 2 pins under the hood, and then counting the blinks of the CEL. See Toyota 4Runner and Pickup: Cheap Tricks

 

[thatoneguy]

Last two weeks with my 22re I drove 150 miles through just over 3/4 tank. However, I'm on 35's, I was drifting, and when I wasn't drifting I was driving in packed city traffic or on a cold engine

 

[justin_geb]

It has been smoking quite a bit. I will look into the sensor when I get around to working on it. And I'm on 32s driving constant 65 with one stop sign most anywhere I go. I shouldn't be using that much gas.

 

[thatoneguy]

It has been smoking quite a bit. I will look into the sensor when I get around to working on it. And I'm on 32s driving constant 65 with one stop sign most anywhere I go. I shouldn't be using that much gas.

Constant highway driving at reasonable speeds should definitely do better. I can net almost 300 to the tank going 55 on the highway.

 

[giro]

Yep, with a stock manual 3.0 in a 92, when commuting 30 miles each way, I was filling up weekly (300-340 miles, normally in the 19-21mpg range). And that was going up and over a mountain pass (8900') to and from work.

But now with working at home, and putting lots of 2-4 mile trips in taking kids to school or whatnot, there's times where the 4runner or Sienna AWD get down to 13mpg.

Your driving didn't change, and you have a CEL and smoke, so there is an issue. Find 5 minutes and check that CEL real quick. You can then see what it says is bad, in the FSM or on this site: Toyota OBD Trouble Codes ?

 

[2ndgengreenred]

I have a 1995 4runner 3.slow. I put a generic air intake on it a while ago in hopes of maybe getting a little better mileage and horsepower, not to mention the mean sound it gives it. And for a while it seemed to make a little difference. But then my check engine light came on. When the light comes on, it drags really bad. Like I can barely go 55 over a hill with it mashed to the floor. The mileage goes to complete crap. I had to drive it this week to get to school and drove maybe 150 miles and went through 3/4 of a tank. I have had some people tell me it could be the catalytic converter plugged up, which I agree, it could be plugged up. But what caused it to plug in the first lace is what concerns me. So before I get a chance to pull the codes in a couple weeks (I'm not going to be driving it until then) any one have any ideas? Would replacing the catalytic converter solve the problem or would it just clog again?

try pulling the positive cable off the battery for 30+ seconds then reconnect it. it should reset the computer and make the check engine light go off for a small period of time 2-3 days depending ion how bad your O/2 sensor is (this is just a temporary fix to make your truck run right so u can at least get around while tracking down an O/2 sensor of finding the real problem)