runn4

To start off I have 95 4Runner 4wd with the 3.0 and 5speed. I am noticing a big drop in fuel economy after my last fill up and have no idea where to start. I went from getting 18.5mpg to getting about 14mpg. Driving conditions have remained the same and I have not noticed any difference in performance.

The only thing that seems a little off is that I am idling fairly high upon a cold start, around 1500rpm +/- 200rmp, once the engine warms it idles normally. also a little while back it blew out some whitish smoke out the exhaust once, I have not noticed any more smoke though.

wyoming9

iTrader: (1)

Are you using the AC ??

More idle time with the AC?

Smelling any gas fumes??

How are you figuring out your gas mileage??

Stetson_md

Look over your gas lines for leaks

RSR

Could be you auxillary air valve:
"Auxiliary Air Valve - should be called your cold idle increase, since that's what it does. It's a coolant-operated, thermostat-like valve that allows extra air to bypass the throttle plate when the motor is cold, increasing idle speed. It is part of the throttle body, below the throttle plate. When hot coolant hits it, the valve closes, reducing the idle speed. It can get gummed up, either blocking the extra air or causing the valve not to close when motor is hot. To test it, screw the idle speed adjusting screw all the way in (the large front-facing screw on the top of the throttle body) when the engine is COLD. The idle speed should decrease, but the motor should still run. Back the screw out to the original position (so you have to count turns on the way in). When the motor is hot, repeat the process. When the screw is all the way in, the motor should stall or nearly stall. If there is no difference in idle speed with the screw all the way in cold and hot, then your aux air valve is not operating properly. Cleaning it may fix it (see below); otherwise you'll need a new throttle body."
http://www.toyotanation.com/forum/80...er-3-0-v6.html

runn4

I have been using the AC about the same if not less for this tank of gas, I have not been smelling any gas and have looked over the lines for leaks and none are apparent. I have been calculating gas mileage by using the odometer reading and dividing by the amount of fuel put it to fill the tank completely. I have used the same gas station for each fill up.

RSR, I will check the Auxiliary Air valve when I get a chance.

RSR

The other thing that comes to mind is that you may have gotten some dirty fuel that really clogged your injectors -- or fuel that had waaaayyy too much ethanol in it (ethanol separating from gasoline in ground tanks is a well documented problem, and ethanol is a solvent which acts to clog up your fuel system -- ultimately "cleaning" your system but dumping most of that varnish/crud/etc into your injectors). That could explain I suppose, but not sure on that.

When's the last time you changed your fuel filter and ran a good injector cleaner like Redline, BG, or Amsoil through?

Slowey23

or it could be your O2 sensor on its way out causing the engine to run a bit rich

RSR

Yep, any failed or failing sensor in the fuel, air, spark system could be causing too.

runn4

I just had my injectors rebuilt so I doubt that is my problem. Ive been thinking it might be my fuel filter as I am not sure when it was changed last, I just bought this about 2 months ago. I ran the last tank pretty low so it might be possible that I sucked up some crud from the tank that is clogging the filter.

On sensors ill have to look more into that, I do not have any engine codes currently.

Ill do the fuel filter and run some cleaner through the system this weekend when I get a chance.

Thanks for the help so far.

RSR

Ding ding ding. That'll do it. With the age of our trucks, next time you remove the bed for any reason, it wouldn't hurt to replace the fuel pump and pump filter (in addition to fuel filter), drop and clean out your tank, replace the soft fuel lines, and the main hard lines if corroding. Replacement tanks are only a couple hundred bucks so really not that bad. Pump and pump filter are ~$150 if buying Denso OEM equivalent. This is on my to do, as you'll find that several folks have been stranded with failed pumps or broken fuel lines on here recently.

Also, if your filter is really old and failing/torn, you could have had some of that crud make its way to your new injectors too...

For the O2 sensor, you usually don't get codes as it's failing (essentially, it's element gets clogged and less able to accurately read) until it fails completely. If replacing your O2 filter save yourself $50 and buy the aftermarket Denso one that's the same as OEM, just different box (get the one with the OEM connector).

bob200587

You should keep track of the MPG for a few more weeks before thinking something is wrong. One fill up showing a poor MPG doesn't really mean much. Sample size is so small.

whitecollarredneck

Could also be your spark plugs. When they get burned up your mileage will drop.