Wife is not happy

[Martinjmpr]

You're also going to be a good candidate for sludge buildup since it seems like your engine never gets up to operating temp and stays there.

I'd suggest more frequent oil changes than normal.

Also, are you using a block heater? If you can use one, I would recommend it. Keeping the engine at a warmer temp will alleviate some of the problems you're having. It will also prevent you from needing to let it idle for 10 minutes to get warm.

 

[hambob]

Go through a couple tanks and recalculate. You'll get a more accurate average

 

[clemson4r]

Yes, my drives are short to work, less than a mile but I've also went on some short jaunts out of town etc just to run it a bit...but i do let the engine run for about 10 minutes before taking off each time I start it. It has been cold here -20 to -10F about every day since I picked it up 10 days ago. the way ive been calculating it just using the odometer -- driving 30 miles, and then refilling..both times it took more than 6 gallons to fill. Perhaps that's just the nature of the beast. I am having the rear drums looked at later this week, looking at bell crank tutorials on here in case that's an issue.

You can easily check if your brakes are sticking by yourself. Drive to the top of an incline and stop, put the car in neutral and let off the brakes. If it doesn't willingly roll backwards, brakes are certainly part of your issue
Max

 

[nodakker]

All great suggestions... esp. the walking to work ones (lol)...might have to start doing that as soon as it warms up around here... this winter has been pretty bad... but in the meantime, I guess I could put a pic of the beauty on my screen saver. (if my wife i reading this i meant her, if she isnt, i meant my runner...)

 

[Ol'Blue]

I agree with all above. The winter has been sucking my milage also in MO. It has been cold this year. As said above, more oil changes. Clean out everything out, fluids, filter, everything. Also, use 91 or 93 if you can find it. My truck runs so much better on 93 and I will pull almost 80 miles more on 93 vs 87. That is allot. As said also I would look and consider new Oxygen Sensors for the truck. I was getting about 10-13 and after replacing that I was back in the 19-20 range in the Hwy. Hope this all helps out. Oh- and go on a road trip on it and fill it and track what you are getting. You should get about 220-275 a tank. That is what I pull.

Blue

 

[MojaveMadMan]

PCV valve is $10 +/- from Toyota. Supposed to help with mileage if it's bad. Either way it is a cheap part and something you can easily check off your list... I agree with the short warm ups as mentioned above, and the block heater. Get in, fit it up and go.

 

[sportrunner2001]

I also live in ND so I know the winters too well haha. I planned on doing a few things this summer to try and get my milage back to where it used to be (or the best I can). and a few maintenance things also.

-clean MAF
-new upstream O2 sensor
-new PCV valve
-new fuel filter
-rear O2 sim (its always been really sensitive to change even back in 01)
-clean TB
-diff fluid changes
-new plugs and wires

I found most of the items on tps.toyotaofdallas.com for a decent price. From what I've read recently, these things should help out with milage but with only going a short distance in the winter the milage goes downhill fast, in high school I got 10 in the winter by letting it idle while waiting for class for 20 minutes a day. hope this helps!

 

[runner823]

Winter gas does have some negative affects on MPG due to the additives and percentage of ethanol being added to the gas. Washington state is 10% max ethanol can be added. But in your case of 5-6 MPG is very excessive - your engine must be running really rich!
I would suggest that you have a pro. diagnose it. Unless you want to throw parts at it.
Well here is my tip if you want to attempt to fix it yourself.
I would monitor your upstream o2 sensor with a voltmeter.
1) bring your vehicle to temp.
2) rev. at 2000 - 2500 rpm
3) back probe input wire of the o2 or connect to the DLC1 under the hood.(if pins are available).
4) your o2 should switching from .20 - .80 volts within 20ms of time. if not you may have a bad o2.
- if your reading is above .6 volts your exhaust is rich - below .50 volts your exhaust is lean.

I would first try to switch to a different gas station and octane. higher the better.
top tier Gas are what Toyota/Lexus, Honda/Acura, Ford, & GM recommends for there vehicles.

Top Tier Gasoline

good luck!

 

[Fireball]

Take it for a longer drive on the highway or in mixed driving and report back with the mileage.

5 to 6 sounds absurdly low and maybe indication of a serious problem.

We've got a 99 that is my wife's daily driver, sitting outside doing a 5 to 10 minute warm-up before driving 5 miles to school and back each day we get 14-15 mpg. 17 to 19 is what we were getting before it got so cold.

 

[MAD 69]

I thought I was getting bad mileage in the winter - a little over 20mpg, in the summer I get closer to 22. I highly doubt letting your engine warm up for 10 minutes is causing your bad mpg's, bring it somewhere to have it diagnosed, they can hook it up to the computer and key you know if a sensor is out or if you have a leak in your gas tank.

 

[Martinjmpr]

Also, use 91 or 93 if you can find it. My truck runs so much better on 93 and I will pull almost 80 miles more on 93 vs 87.

Unless the engine is knocking or unless OP is running a supercharger, higher octane will not help and is a waste of money.

High octane only benefits high compression engines, which the NA 3.4 V6 is definitely not.

 

[Grenvilleter]

My mileage is horrible right now ! Nothing wrong with the truck but it is entirely dependent on outside temperature and the short runs I have been doing.

I'm doing about the same as you right now in the mileage dept.
I have also found when the outside temp gets up to the freezing mark, my mileage comes up considerably.

Do not spend a lot of money on diagnosis right now but limit your idle times, put a cardboard in front of your rad and keep a record of your fill up's (quanity) and mileage driven.
I think you will see a difference.
Fill up every couple days even if its just topping off a couple of gallons and you will also be able to track the difference outside temperature makes.

I do not have real time coolant temperature reading but Shootmymime summed up all whats happening.

If it was not sub-freezing and you were getting 10-15 with normal highway driving on a stock truck, I would then look at other problems.

Also curious why everyone says to clean your fuel filter to improve mileage.
I can't figure that one out.

 

[Brique]

I think I've figured out your problem. You need a new comporator and traverse shift modulator. I can sell you them, but I'm afraid they don't come cheap.

 

[Ol'Blue]

Unless the engine is knocking or unless OP is running a supercharger, higher octane will not help and is a waste of money.

High octane only benefits high compression engines, which the NA 3.4 V6 is definitely not.

I will agree with you on this, but my engine just runs and pulls much better gas mileage on better gas. Granted, I would love to have a supercharger and a even better reason to run 93

Blue

 

[Grenvilleter]

I will agree with you on this, but my engine just runs and pulls much better gas mileage on better gas. Granted, I would love to have a supercharger and a even better reason to run 93

Blue

In Ontario where I live, the gas labeled "premium" or "super" and has a higher octane rating (92-93), has no ethanol added. This could account of a better mileage figure if the same happens where you live.

With that said,quite a few years ago, I owned a brand new Ford Ranger ('87)and drove it daily 150 miles round trip to work. After about a year of running on regular, I was noticing a little miss on occasion so I switched gas to a brand that claimed they had cleaners in it and went to high grade/octane.

It was a standard transmission and immediately I noticed, on corners I had to downshift to 2nd gear I could now do in 3rd gear. My mileage went up about 75 km /tankful. The stuttering cleared up and the difference in mileage more than made up the difference in cost.
This was before ethanol was being put in the gas.

 

[99 sr5 highlander]

Being in 4wd also wrecks your mileage, along with idling. A Scanguage II may be a good investment, it shows you fairly accurately real time coolant and trans temp, and mpg. Ive found it useful and during my short drive to school in traffic 10mpg is not out of the norm.

 

[Skinfaxi]

Unless the engine is knocking or unless OP is running a supercharger, higher octane will not help and is a waste of money.

High octane only benefits high compression engines, which the NA 3.4 V6 is definitely not.

Not true. Most vehicles since the mid '90s have adaptive spark/knock feedback logic. The control system will advance spark (up to a certain amount) until knock is detected, and then back off slightly. Thus, higher octane will result in more torque and lower load for a given throttle position. When you get aftermarket tunes/flashes, mostly all these guys do is fix the spark at the higher values, then tell you to run high octane.


All these frequent cold starts are definitely hurting the OP's fuel consumption. With starts below zero, the lost fuel compensation tables are probably maxed out. With short drives, he's likely never getting hot enough to stop commanding lost fuel lambda control. Combine that with lighting off the catalysts, and the car is commanding a TON of fuel on starts.

That said, 5-6mpg is still suspiciously low.

 

[hearno]

5-6mpg is still suspiciously low.

Yeah... you can throw all the "tune-up" parts you want at it and it's still not going to fix a 75% reduction in average mpgs. Most 3rd gens are getting around 20, right? Has anyone mentioned checking for a fuel leak? That would account for your situation. Also, you're not calculating your mileage correctly, extended idling will throw everything off. I understand you're saying you're getting 100 miles per tank but your driving habits aren't normal either. Fill up completely, get on the highway, set the cruise control at 55 and drive somewhere. Then drive back under the same conditions. I'd shoot for 100 miles round trip. Fill up again. See exactly how much fuel it took to put 100 highway, cruise control miles on it. That will give you a better idea of your actual mpgs to see if there is a mechanical issue or its just your driving habits/routine that are causing the low mpgs you're getting.

 

[HiLife]

It's not as cold as where most is but, this is what I have been experiencing...
I have been filling up my tank noting the mileage, and noting the miles driven on the next fill up. Been doing that for 5 years. Idling for 10-13 minutes on 40 and below mornings. Doing this only wastes 13 miles per tankful. I feel that's a small sacrifice to have a properly warmed up engine. My work place is 6 miles away.

The cardboard sounds like a good idea. I see them on 18 wheelers all the time. Doing the cardboard on my 00 will definitely cut down time to warm it up. I'll try that.

 

[thebrandon]

Get rid of the wife. Then she won't be mad about your mpg .