Hey yall..
Ive got a 1995 4runner with 254k miles that runs strong for its age and mileage.. Over the last 6 months I have noticed a huge drop in gas mileage.. I know the 3.0 isnt known for gas mileage but things have gotten out of hand... The truck has been maintained, filters, fluids, tune ups, and more.. This morning, I drove 13 miles to work and watched the needle move as I was driving.. Ive burnt a qrt tank within a day and I dont drive that much...

I completely understand that this could be caused by a number of things, but I would really appreciate some help in narrowing it down.. Is there anything that comes to mind that would cause such a HUGE drop in gas mileage.. Keep in mind, Im not talking about loosing a mile or two per gallon, Im literally watching the needle move as I drive....

Please help
N Johnson

 

I would check your tank and all the lines, could be a leak? I'm guessing you would smell a leak, I know for some reason I can smell even a tiny bit a far distance, but if its a line that only leaks when under pressure you might not.

 

What are your mileage numbers like? I used to get 13 to 14 mpg before I moved to Montana. Now I get 16 to 17 mpg. Your tank isn't as weird shaped as many out there, but it still doesn't show the level exactly and the needle will move at different rates depending on how full it is. Once mine gets close to a quarter full the needle doesn't move much until it quickly gets close to the empty light.

 

check for leaky fuel injectors and tire pressure. and as angrydog suggested, leaky lines and tank. are you running rich at all?

its pretty intense that you can witness the needle move like that, the only time i was able to do that was in my buddy's '68 buick riviera with a 468 ci in it (8-9 mpg). 3.0 is not known for the fuel economy, but there is no reason you cant be getting at least 14 mpg, even with a tired motor (no offense, considering mileage).

 

Check the fuel pulsation damper on the passenger side fuel rail, just under the back passengerside of the intake plenum. With my 3.0, i started seeing a major drop in mileage. the breaking point was when i went through a quarter tank driving to school (7 miles). the damper will start to leak fuel from under a plastic cap when it is worn out. the leak becomes more apparent the longer it is run while damaged, and in extreme scenario's, can actually cause a fire, due to the fact that the leak drips fuel directly onto the exhaust crossover. i'm not saying this is your problem, but i figure'd i'd throw my story out there to help ya out.

 

THANKs GUYS!!! Really appreciate the input... @ 250000, I hear ya.. I feel like I go through a qrt tank everytime I drive to work (13 miles).. I drive this truck because I love it and dont want a car payment, but at this rate, it may be cheaper

thanks, I ll check these things out..

 

ya, on a high school kids budget, that just about killed me lol.

 

Best of luck to ya Just wondering though were there any other slight problems that have come up recently that you noticed along with the gas mileage problem?

 

Im not sure if a 3.0 has a fuel pulse damper, but if it does and its leaking that would kill your gas mileage. Also check or replace the 02 sensor, if its original or has a lot of mileage on it just replace it. The computer uses the 02 sensor to set the air fuel ratio and when they go bad that will effect your mileage.

 

i posted that about the damper because i had to replace mine. I forgot to post in that right before i replaced it, i did start smelling fuel.

 

Ditto to both. Check the damper SOON because it can cause a fire that can burn your truck up & a garage/house with it if it's not parked outside.

 

He is right about the fire issue. As i mentioned above, the damper sits about 6-8 inches above the crossover pipe on the driver's side. I have personally seen two 3.0 trucks that have burned up because of this...

 

I had a similar failure of the fuel pressure damper (on the passenger side back of the fuel rail under the plenum). It was spraying fuel on the firewall out of the plastic cap when under pressure.

You should be able to smell fuel really strong though if this is the case. That is how I found my leak. The smell of gas was really strong when I parked and got out of my 4runner. I stopped driving it and got the parts to fix it ASAP so I did not drive it to notice any gas mileage loss. I was worried my truck was going to explode.

Its an expensive little "bolt" so make sure that is your problem before you try and throw parts at it.

 

I wasn`t sure about the damper on the 3.0, but the funny thing is, is that the fuel damper on my 86 4Runner 22RE is leaking because the screw came out of the bottom, so i have one on order and when it gets here im going to put some JB Weld on that screw so it will not come out again.

 

I JB welded mine on my runner as well, a yr ago, but my 3.0 gets bad gas mil., I think it's my 02.

I'm changing it out this weekend, and I'll post the results.I can tell a big difference between no check engine light, and when it comes on.

 

A bad 02 sensor can deffinatly kill your gas mileage, have you ever removed and cleaned the throttle body ?, it would be a good idea to do that as well.

 

Did this problem ever get solved. I literally watched my gas gauge drop on my way home last night. I didn't notice any leaks or smell gas. Would an O2 sensor go out suddenly or should there be something else to look for?

 

I checked around yesterday and made sure there weren't any leaks, I am going to replace the O2 sensor tomorrow, but I am still concerned that may not fix the problem. My main concern is that I drove to work with no problem and then the problem started out of nowhere on my drive home. Is there anything else that could cause this to happen? Anyone else have a similar problem they've fixed?

 

It's got to be a leak.

 

Thanks TNRabbit, I will definitely take a closer look for leaks while im doing the O2 sensor tomorrow. After I got home today I took a look at the FSM for other ideas and there are 20 different possibilities listed!! I hope its simple, its my only ride and I dont have the experience to get this fixed in a timely manor.

How strong should the gas smell be if it is a leak? I know how strong gas smells and all, but would I be able to smell it while im driving or just while im outside the car? I havnt got a chance to look around in the light since its dark by the time I get home.