1st gen worse MPG. What could be the Problem?

Hello all,

I have a 2005 toyota tundra, double cab, 4x4, 4.7L with 180k miles. The first 14 years with the truck I always got around 15 city and 17 hwy. The past couple of years it's been 11 city and 13 hwy. What could be the problem?

About the time this happened my truck started throwing me Oxygen Sensor codes. I have since replaced the two forward O2 sensors, I have changed the spark plugs, I drive pretty slow, good tire pressure and balanced, I have tried premium gas it doesn't really help. I have always used synthetic mobile 1 oil and changed at 4,000miles. What could be the issue besides age? I almost happened over night.

 

What brand oxygen sensors? Denso?

 

$140 Sangyue Air Fuel Ratio O2 Oxygen Sensor 1 & 2 for Toyota Tundra 2005 2006 4.0L 4.7L Upstream +Downstream 4pcs

https://www.amazon.com/dp/B07HLXZ2H6?ref=ppx_yo2ov_dt_b_product_details

Sangyue Air Fuel Ratio O2 Oxygen Sensor 1 & 2 for Toyota Tundra 2005 2006 4.0L 4.7L Upstream +Downstream 4pcs. I bought off Amazon and had really good reviews

 

@shifty` is gonna eat you up for that lol.

 

Non denso sensors do not work right on these trucks.

Buy denso ones from a local parts store, rockauto or summit racing. Anywhere that doesn't have 3rd party vendors (ie Amazon, ebay or walmart.com).

 

Have the O2 codes gone away? If not, I would check the wiring (especially grounds).

Do you have any exhaust leaks?


Besides the O2 issues, have you switched to aggressive tires? Have you ever checked valve lash? Compression and leakdown tests might help narrow potential causes...

 

This is why you should only buy OEM sensors (Denso), possibly?

But I'll say, I track my MPG religiously via smartphone app. My 4WD '06 averages around 12mpg (barely) with mostly city driving, and 15-16mpg if mostly hwy.

I'd be curious to know how you're tracking mileage *and* if you changed tires recently (due to size and how it impacts mileage #s). I'm running stock sized tires and my numbers are meticulously tracked. When I see guys on here claiming some of their 4WD truck MPG numbers, I'm extremely skeptical.

 

Any parts bought on Amazon, eBay, Walmart are suspect because those sites are infested with counterfeit parts. Spark plugs and O2 sensors are near the top of the list of parts to be weary of.
I would also recommend Denso O2 sensors. But since you already have the aftermarket sensors installed, I'd leave them be for now and move on to other possiblities. If you don't find any gains, then revisit the O2 sensors.

- What spark plugs did you use for replacements? Did you get them on Amazon too? (If so, consider replacing them with Denso or NGK from Rock Auto. And be sure to check the gap.)
- Have you ever cleaned the Throttle Body and Mass Air Flow sensor? (these are cheap and easy to do DIY, and can have a noticable impact on drivability)
- Have you inspected the front and rear brakes for dragging?
- Have you changed the gear oil in the axles and transfer case?

 

On this point - I'm still seeing improved throttle response after cleaning my MAF a couple months ago. I thought it was a fluke, or totally mental/placebo, but I finally found the lost power my truck was supposed to have.

Best part is, I'm still seeing the exact same craptastic gas mileage, but only because I can't keep my foot out of the accelerator pedal

 

This is a timely post

I have a 2000 mile trip coming up, and recently noticed that my truck is getting 10-11 MPG, mixed.

This summer it was as high as 15 highway.

Today I was down 1/4 tank on the gauge, 4.5 gallons, after 47 miles

I'm trying to figure out if something is wrong, or its just winter.

I have never cleaned my MAF or throttle body. Should I? does that actually matter?

 

Mine had never been cleaned. After 16 years and only 70k-ish miles it actually helped. Previous Owner(s) drove on a dirt road frequently. May or may not have something to do with it.

 

Both the previous owner and myself mostly drive on dirt roads. Previous owner did the timing belt right before he sold it to me, and replaced an 02 sensor. I wonder if he used an OEM sensor and or cleaned the throttle body while doing timing belt? Guess I better check those out.

 

once winter blend fuel and cold temps kick in, my MPGs drop too. from 13-16 all summer, to 10-14 in winter.

 

How many trips did it take to go 47 miles? Is it garaged and/or heated?

Every cold start (especially Montana winter cold start) wastes a ton of fuel just getting the engine and drivetrain up to operating temperature.

There's an interesting video on youtube of an Alaskan starting an old Ford at -50. Even with a block heater, the manual transmission's gear oil was so cold & gummy that his engine would stall if he let the clutch out in neutral. That's obviously an extreme case, but all the grease in the wheel bearings, the gear oil in the diffs, transmission oil/fluid, the power steering fluid, etc have excess drag when cold.

 

It was two trips. One 36 miles, one 9, It's not garaged. Current Temps are about 15-20º....and thinking about it, only one cold start, as it was all warmed up when I got gas the first time obviously.

You have a good point. I'm probably being paranoid. I got a little PTSDed on car repairs last winter (not my truck) and have been kinda a vehicular hypochondriac ever since.

I too lived in Alaska, with my 93 toyota and recall those days. I found out that your rear diff oil can 'freeze' so solidly that you can't move an inch. I used to get up early for work, pour some kerosene in a soup can half filled with sand, set it on fire and set it under the rear diff to warm it up enough to move. Battery heater, block heater, and oil pan heater don't do you much good if the wheels won't turn...and then when they do turn, the seal is frozen to the driveshaft and tears it out. Switching to synthetic fluid solved that problem.

 

wow. I thought i had it bad with my -50 coldest days here in MN.

 

actually -50 or wind chill -50?

'Real' -30 and lower is about where I started have diff oil freezing problems, etc. Coldest I ever saw it there was -52 and that was only for a day. The all time record for Fairbanks was -66 so not far off.

But we would months at a time where it never got about -30.

 

Usually windchill -50. I think I've seen real -50 once maybe. so far the coldest this year has been -20.

 

In my experience, cleaning the throttle body helps more for smoothing out idle and off-idle performance.
The MAF sensor can have an affect on the overall driveability throughout a wider throttle range. My last vehicle was an '02 Runner with the same 3.4L 6 cylinder that was used in 1st Gen Tundras. When I first got that truck it had about 100K miles. It was in great shape, but was just a absolute turd in terms of power. I could be going 35mph and floor it, and the transmission wouldn't downshift. I could manually make it downshift, and then it would accelerate, but even then it was horribly slow and underpowered. Towing a 3000 lb pop-up camper up a mountain pass was a 25 mph affair -- no kidding. And the fuel economy was horrible. I did the usual suspects: spark plugs, air filter, fuel injector cleaner -- nothing helped. I was a member of T4R.com and the MAF sensor cleaning is a well known maintenance item on that forum (at least among the 3rd Gen crowd) -- I believe Toyota calls for it to be done every 30K miles. Anyway, cleaning the MAF sensor completely transformed that truck.

Having said that, I think the transformation may have been so dramatic because transmission in the 4Runner is more electronically controlled than the one in our Tundras -- so input from a sensor like the MAF could have a larger affect. Although I'm not certain of that. I know for a fact that transmission would "free wheel" more when you let off the accelerator. RPMs would drop and it would feel like you were coasting more.

The bumper sticker version of this post: clean the throttle body and MAF sensor. It's so cheap and easy, it makes no sense not to do it.

 

I was shocked at how much it changed things for me. Could just be for the reasons you mentioned: It's an '06, has the better 5spd trans, more electronics, who knows?

I didn't expect to see any improvement with just 70k-ish miles, but it was very, very noticeable.

 

Is there a technique to it? Or is it just a matter of giving it a blast with carb cleaner?

 

I'd use MAF cleaner - safer for electronics

 

They sell a specific aerosol can of MAF Cleaner at any Vatozone . . . not sure of the chemistry . . . but it worked for mine

 

CRC MAF cleaner is my brand of choice.

The German guy on YouTube who does Toyo maintenance and really breaks it down for the layman has a good video on MAF cleaning. Our MAF isn't in this location, it's on the intake between the filter and throttle body (link) but I suggest checking it out if you've never done it before. Let the MAF come to room temp before cranking up the truck, it'll be cold as shit when you finish, and will cover with condensate if there's humidity in the air:

https://www.youtube.com/watch?v=DDgbiHe__j4

 

Thanks a lot. I'll be doing this as soon as I can make a trip to town and get some. Sensors are somewhat of a mechanical 'blindspot' for me, I have cars that I've pulled engines on, but never replaced a sensor....just one of those things I've been lucky enough to avoid problems with and so never had to learn how to fix.

I'm a little nervous about this upcoming long trip, in my old truck that I normally don't take more than 60 miles from home so trying to get a few things like this done this month.

 

I haven't cleaned mine and I'd bet previous owner probably never did either. Might put this on my to-do list.

 

Went into town today to get some MAF cleaner....one of my tires looked kinda low, and that was when I remembered I aired them down a few weeks ago to get up my driveway. All four where at about 15 PSI......wonder if that could have anything to do with it?

 

Yeah, that might affect things a wee bit.