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Hey there, I just bought a really 2004 Toyota Tundra Double cab limited. I've only had it for a few weeks but I've noticed it seems to be lacking a bit in power, leaking a little antifreeze though the only indicator is that the reservoir goes to empty without a drop/smell of antifreeze anywhere. I'm also getting 480km to 90 litres of gas, or 290miles to 23.7 gallons. I know it's a V8 but this is brutal mileage. It has a cold air intake placed by the previous owner and sits on 31" BFG all terrains. I have had it at the shop now for 2 days, and they cannot find what the problem is. MAF sensor was fine, as was the air temp sensor. There was a vacuum hose hooked up incorrectly to the intake tube of the cold air intake but that has been since corrected and moved to the proper place. It was mostly highway/logging roads, driving very conservatively. My concern is that it may be the head gasket. Any ideas before I go down that expensive road!?!?!? I'm sure it has something to do with the computer, I just don't know what...or how to find it, seems as though no one can.

Spark plugs have been replaced, oil has not been changed and there is a bit of a ticking sound at high speeds.....

If anyone can help I'd be forever grateful! The mechanics just can't find the problem. OH, and after I took it home from the shop, 15 minutes later drove to work and check engine light came on....brutal!!
 

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I heard a ticking on the driver side of my engine block while idling in park. I blew the spark plug for the cigarette lighter. Also had mud lodged in my head lights. Honestly I'm not sure what the problem was, but I rewired the cigarette power lines (one was frailed), replaced the spark plug and changed my head lights. The ticking went away.
As for the power lose problem, I've felt the same thing. Your engine sounds high pitched, feels like your siphoning gas when you accelerate before your truck shifts. Normally starts about 1800 RPM. I changed my oil 300 miles early and it felt fixed. I have occasional siphoning sounding noises where it feels like my truck isn't at max power but I haven't cleaned my engine block since the last time I went mudding and I'm chalking it up to lodged mud.
As for the gas problem I wouldn't know where to begin, I'm no mechanic. Where did you get it inspected? Have you done the basics, like getting your timing belt swapped at 90k? I waited until 95 and it def could've used a swap before I bought the truck (purchased at 88k). I'd change your oil before making any rash decisions, I know sometimes shops put "last oil change date" stickers and some put "oil will need to be changed at xxx date" stickers, and a stoned Jiffy Lube employee won't read the fine print I promise you.
Hope this helps.
 

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My brother had a similar experience many years ago with an F150. The problem was a failing (not failed yet, but no longer working correctly) O2 sensor. The engine computer did not flag it as an error, but the result was a much richer air/fuel mixture than it should have had, which means some of the fuel was being fogged through the cylinders without being burned. He replaced the O2 sensors and the problem was cured immediately.

Keep in mind what can effect fuel mileage that could be wrong:

air resistance

engine friction

drive train friction

tire rolling resistance

mass air flow sensor

O2 sensors​

With a lot of drag and/or friction and/or rolling resistance, it takes more power to push the truck down the road.

With an incorrect air/fuel ratio, the engine develops the needed power, but it wastes fuel doing so.

Now, what is most likely the culprit, given what you've checked so far?
 

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Hey CedarPark, thanks for the reply. I wish it was something that simple but I've done everything remotely common to try and fix it!

Remy700P, can't remember what the code was that the shop said, however they said that the long term fuel trim was 20% higher than what it should be. O2 sensors up stream, the first two were definitely reading "weird" they said. Potentially this could be the problem, however they weren't initially all that bad, and they weren't throwing up any "normal" wear and tear error codes. We've checked everything, MAF sensor cleaned, throttle body was taken apart and looked at in the hopes there was some anti freeze leaking into it causing the O2 sensor problems, sadly throttle body was fine. We did find the water pump is leaking antifreeze, but not until the coolant system was hooked up to continuous pressure all day. Perhaps it's the ECU or maybe it is the O2 sensors. Going to try an O2 sensor from the wrecker this week and see if maybe it is just those two first O2 sensors. Everything else checks out, fuel pump, filter, plugs, e-brake, you name it. The shop is at a loss, and I hate to think that I'll have to go pay premium prices and go to a toyota dealership to maybe find the cause!! It is, I'm almost certain something electrical, has to be something with the computer, just don't know what......of course we may luck out and have it be the O2 sensors....but I'm not entirely convinced. It's just not running right, and at 8mpg city/highway there's no way my gas guzzling tundra can be guzzling that much gas!!!

Anyone else have any ideas we may be missing? I apologize in advance if I've forgotten to list what else we've checked.

DJ, i'm almost positive that it's an incorrect air/fuel ratio....but how or why has stumped the shop..... Hope we can figure it out soon.....
 

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... can't remember what the code was that the shop said, however they said that the long term fuel trim was 20% higher than what it should be. O2 sensors up stream, the first two were definitely reading "weird" they said. Potentially this could be the problem, however they weren't initially all that bad, and they weren't throwing up any "normal" wear and tear error codes.
As I stated about my brother's experience:

"The problem was a failing (not failed yet, but no longer working correctly) O2 sensor. The engine computer did not flag it as an error, but the result was a much richer air/fuel mixture than it should have had, which means some of the fuel was being fogged through the cylinders without being burned."​

The shop has diagnosed your truck the same.

The shop is at a loss ...
The shop should not be at a loss. It has diagnosed that your fuel mixture is exceptionally rich, but it hasn't completed the analysis of the situation. The analysis is:

The fuel mixture is very rich, we haven't found anything wrong anywhere except that the O2 sensors are reading "weird". Bad O2 sensors can cause rich mixtures. This indicates it's time to replace the O2 sensors. The only way to find out is to replace them and see if it cures the problem.​

... and I hate to think that I'll have to go pay premium prices and go to a toyota dealership to maybe find the cause!!
You shouldn't have to. Knowing what you've described, if it were my truck, I would put new O2 sensors in (i.e. both sides; if one side is bad, then likely the other side is too) and see what happens. Likely that's what the Toyota dealership would do also. You can do that without having the Toyota dealership touch the vehicle at all and so save the cost of having Toyota tell you what you already know.
 

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How about the thermostat being stuck open? :beatsme:
 

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hi, i get 278mpg when the fuel light comes on. i have a very heavy foot. a ton a city driving. also did a few things to mine. cai, headers, cat back exhaust, unichip, & 295/45/20's. added a lot of extra's, so it's heavy. Gorilla p.s. a scan guage2 xguage is great to have.
 

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Discussion Starter · #9 ·
Hey DJ, I agree about the O2 sensors, and I'll probably go pick a couple up today from our parts store, I think they have them in stock. Hopefully that will cure the problem!!

Jack- not sure about the thermostat being stuck open, figured when we do the water pump and timing belt we can have a look. Maybe I should look at it sooner? Not sure how expensive those are, maybe I'll see if they have one in stock and isn't too expensive I'll throw that in today too....?

Gorilla- Damn about your mileage, I will be levelling/lifting the truck and putting probably 33's on it, so no doubt the mileage will go down the toilet soon...not to mention either a canopy/camper at some point and of course then a loaded truck when we go on trips with it.....maybe I need to put in a bigger V8!!!

Thanks for the help, hopefully it'll be fixed soon....keep you updated.
 

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I'm also getting 480km to 90 litres of gas, or 290miles to 23.7 gallons. I know it's a V8 but this is brutal mileage. It has a cold air intake placed by the previous owner and sits on 31" BFG all terrains.
290 miles on 23.7 gallons equals 12.2 mpg. That's not that bad. Winter gas plus low air temperatures plus short trips plus oversized tires and 12.2 mpg sounds normal to me.

I have noticed the gas mileage for my truck has been abnormally low this winter, bouncing around 14.5 mpg. I have put that down to the unusually cold temperatures. My truck gets close to 18 mpg in the summer and averages about 16.5 mpg year round.

Best thing you can do for winter gas mileage in Canada is to install a block heater, particularly if you have a short commute. Second thing to do is install a new Toyota coolant thermostat. If you feel like spending the money, you could also replace the two upstream oxygen sensors with either Toyota or Denso parts as the oxygen sensors have the most direct influence on gas mileage. However, I've become skeptical of the idea that oxygen sensors become "weak" somehow and no longer replace them as a preventive measure if they're not throwing a code.

On your coolant loss, if the coolant has been drained recently - before you bought the truck - it will take a while for the cooling system to top itself off by sucking coolant from the overflow tank. If that's the case, your coolant "loss" will soon stop. Another possibility is that your water pump is leaking through the weep hole. That will be more or less invisible.
 

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Discussion Starter · #11 ·
Thanks mibro, I ended up replacing the upstream O2 sensors today and will get the water pump done this week hopefully, as there was a leak found there. I wish poor mileage was due to our winters, but I live on Vancouver Island, where our winters are most peoples mild springs. Rarely below zero, so doubtful it is that. I filled up the tank today after replacing the sensors, we'll see what happens over the next week or so. Thanks for all the input!
 

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Things that do affect MPG on your truck:
MAF
MAP
O2
Air temp (included on the MAF)
OIL TEMP (I don't quiet remember for this one)
COOLANT TEMP

And the MOST INPORTANT ONE.... Have you CLEAR THE ECM OR DISCONNECTED THE BATTERY RECENTLY??
If you have done the ECM or Batt ; Give it till the 3 time you cycle the fuel (run low and top off) using the truck. Soon after that the ECM should be fully ready with the new FUEL TRIMS. (Some people refer to the fuel trims as CAM TRIMS so don't get confuse with the terms)
 

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Air filter clogged...
A clogged air filter does not reduce fuel mileage in a vehicle with fuel injection and closed-loop control over the air/fuel ratio. The Tundra is such a vehicle.

Go read:


The conclusion stated therein:

The goal of this study was to explore the effects of a clogged air filter on the fuel economy of vehicles operating over prescribed test cycles. Three newer vehicles (a 2007 Buick Lucerne, a 2006 Dodge Charger, and a 2003 Toyota Camry) and an older carbureted vehicle were tested.

Results show that clogging the air filter has no significant effect on the fuel economy of the newer vehicles (all fuel injected with closed-loop control and one equipped with MDS). The engine control systems were able to maintain the desired AFR regardless of intake restrictions, and therefore fuel consumption was not increased. The carbureted engine did show a decrease in fuel economy with increasing restriction. However, the level of restriction required to cause a substantial (10–15%) decrease in fuel economy (such as that cited in the literature) was so severe that the vehicle was almost undrivable. Acceleration performance on all vehicles was improved with a clean air filter.

Once it was determined how severe the restriction had to be to affect the carbureted vehicle fuel economy, the 2007 Buick Lucerne was retested in a similar manner. We were not able to achieve the level of restriction that was achieved with the 1972 Pontiac with the Lucerne. The Lucerne’s air filter box would not hold the filter in place under such severe conditions. (It is believed that this testing exceeded the design limits of the air box.) Tests were conducted at a lower restriction level (although still considerably more severe than the initial clogged filter testing), allowing the air filter to stay seated in the air box, and no significant change was observed in the Lucerne’s fuel economy or the AFR over the HFET cycle.​
 

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You may have some issues with your truck that I wont attempt to diagnose. I think mibro said it all. Your mileage is not that bad this time of year. Even if there are issues with the truck that are found and fixed you probably wont see a lot better numbers. I am getting about 340 a tank with mostly city driving during the coldest months. Summer I see about 480 with same driving. Probably the best I ever got was 550 with a bunch of big highway runs. And yes, those are kilometres I am quoting not miles. It is starting to warm up now with most days around 8 C and I am already seeing an improvement in my average. Numbers are slightly better on this truck vs my 05.
 

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Hi everyone. I'm new here but, have been lurking for a while. Was on the Frontier forum until I got a 2004 Tundra doublecab/4.7 with 82K. Love the truck. So does the wife since the Frontier was somewhat cramped in comparison. I have been reading this post and was wondering if anyone has experienced poorer gas mileage since the weather had warmed up? I put slightly larger tires on the truck and did not have any drop in mpg until it got warm. I was at 18+ mpg in cooler temps and now am at 16. I changed plugs about a month ago using NGK's. Wondering if they were gapped correctly? What gap do you all use? I went by the book for the motor but the old plugs were gapped wider (from age) and were the Denso plugs which I am assuming were original plugs. They looked pretty good to have so much life on them. Any ideas? Thanks in advance.
 
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