Ok. I have a '91 4Runner with a 5" suspension lift w/ 33" MTRs, automatic, and the 3.slow and over the past couple of months my gas mileage has slowly gotten lower and lower to where I am sometimes getting between 7 and 8 mpg. And with the gas prices these days, I be spending $25 every 4 days to fill up. About two weeks ago I decided to do a tuneup on the engine which has 190,000 miles on it, but it still runs really smoothly. I replaced the Oxygen sensor, new plugs, new wires, new air filter, and Chevron fuel injector cleaner. But about every 5 miles I can still watch the gas gauge go down. It's actually pretty depressing after all the work I've put into it and now I have to let it sit in the driveway because I can't drive it. I really want to do the 3.4 swap or shortblock with aftermarket intake and all that but I dont have the money right now. So does anyone have any other ideas as to why my engine is sucking this much gas now? I've even tried keeping the RPMs below 2500 as I putt back and forth to school every day but doesn't seem to help. ANY suggestions please!!!

 

Several years back my mileage also dropped to 7 MPG.
I could watch the gauge move.

I have a post here on it from long ago.
$500 or less later (may have been $300, I forget) it was running great.

The dealer took out my injectors and had them ultrasound cleaned.
They were very bad.
http://www.pnw4runners.com/tech/flowtest.jpg

But mine also bucked like a bronco on the road from the bad injectors.
Since your rig is running good, it may not be them.

 

orginal cat. conv.?

mine was clogged at 125K, I was suffering from the 10 mpg stuff with 31s and 4:56s. Well I installed a Test-Pipe for a tempory fix and my mileage went up to 18-22mpg. Exhaust now sounds like poop.. LOL

 

Yeah I was really thinking about having the injectors cleaned because I guess it couldn't hurt after 190,000 miles. How much does having the cleaning done cost? And how much do cats usually go for? I thought they were kind of expensive. Could you feel a difference in power after you replaced it? Sorry about all of the questions. I've just run out of options and it's making me seriously doubt my ability to keep it and keep driving it if it gets any worse.

 

This could also be my issue. I am spending $60 every 3 days.

This may be related, when I'm going about 30mph and my foot is very slightly on the gas while I start to slow down, the truck starts to buck and jerk back and forth. Letting off the gas or pressing it harder gets rid of it.

 

yeah I'm glad mine hasn't started that yet, but who knows.....it could start any time at the rate I'm going. I can't believe how fast I can watch the gauge go down.....it's really depressing that you put all this work into it and then can't drive it because it costs so much, but I guess I'm going to try and get my hands on a cat. converter and see how that works!

 

You might want to have them just cut the cat off and weld in a pipe in place. would be a very cheap thing to do and its an easy way to see if your milage improves

 

I guess I could try that but I've heard it's hard on your engine and doesn't do it any good to take the cat. out, and I have to get it inspected in a couple of weeks anyways, so hopefully I can find a way to get it to pass or I won't have wheels for a while!

 

Change fuel filter... sould like it could be that problem

 

"ALLALUYA....." Finally some one has the same problem I have! I have talked to so many people about it and they all look at my like I'm stupid!

I'm pretty sure its my injectors too. I have run one bottle of injector cleaner through it and it's helped a little. I'd really like to take mine out and have them cleaned and calibrated, but I don't have a second vehicle. I think I'll do another treatment and see how it goes. Let me know what you try.

Hope I didn't Hi-jack

Erich

 

I just had mine checked out for much the same problem ,they found that one of the temp sensors was reading incorrect(resistance was wrong),so basicly the ecu thought it was running a cold ,when it was actually warm.
its been to early to say if this has made much differance yet as i need to fix my exhaust as well (i have no cat)
hope this helps

 

Do you drive with your left foot on the brake? <Kidding...>
Ever think about getting a 5-speed? <grin> Toyota autos are really good but that could be the problem also.
I had the bad mileage problem happen to a brand new Toy I bought... it was an '85 SR5 pickup with the 22RE (and 5-speed.) From day one it was hard pressed to get 10 mpg. Ran like a dream. Damn dealer was no help - "We can't warranty gas mileage." A nearby dealer service manager listened to what I had to say and agreed that 10mpg was not acceptable. He invited me into the shop to watch as they tore into it. Turned out to be a faulty head gasket! They had folded it when they installed it at the factory. Also, fuel filter, air filter, low oil level, and clogged cat can all do possibly do it. If you have to replace your cat I've seen them on ebay for around 30 bucks. Can't say how good they are.

 

Did you try to use Seafoam. That will make it run good again. But you would prolly have to replace the cat anyways. Tons of black smoke.

 

By the way Tank, that is a nice looking runner. Nice to see someone still feels 1" of lift ain't nuthin...

 

Flamedx4, thanks! Yeah I would be pretty mad too if they gave me something getting 10 mpg. I can just remember last year right after I got the lift and tires that I could still get like 16 to 18 mpg, and it's just dropped ever since. I put alot of work into it and I'm not about to sell it to some kid and let him get everything out of it for like $2,000 after I've spent WAY over that to get it this way. They wouldn't understand the time and effort it takes to do all of it yourself. But anyways, yeah I'm taking it in to the dealership to have them look everything over, do a full tuneup, put it on the machine and see how they think it's running and hopefully get the injectors cleaned. Has anyone else had the injectors cleaned on theirs and did it make a dramatic difference?

 

What is Seafoam? I just got a new cat would that mess it up?

Also....had do you tell if your o2 sensor is bad???

If this stuff doesn't help, I say we go to the salvage yard and swap our motors for some old Geo Metro 3 cylinders.

 

I had the injectors cleaned in my 22RE 4Runner at about 140k. They added something to the fuel and fogged stuff into the intake while it ran for an hour or so. Rolled smoke like crazy. Smoked for a bit after I took it home, then was fine. Dramatic difference in power. But I wasn't having any mileage issues, I had rough running condition that they diagnosed as injectors. Worked like a charm.

 

Get some BG 44k and it will definitely do the job...

 

I don't know if you all have heard of "Motor-Vac". I heard about it a while back but haven't tried it. It's supposed to be a complete fuel system cleaner and I've heard it works real good. Its around $150 I think.