REALLY bad gas mileage

Could be a host of things with that many miles. Fuel, emissions related possibly. I have the same size in a mud terrain and always get between 16-17 in town. Little better cruising along at 65mph. I'd second the injector cleaner. Try that Lucas stuff. It actually helped my pickup at one time which I think is odd as I think that stuff is just snake oil.

 

Dear NodNarb,

You certainly have done your homework as far as finding out the culprit behind your Tacoma's weak gas mileage. I am sure once you dive in and start cleaning up your code problems, your gas mileage will return to where it should be.

Good Luck,
Paul

 

i just took a long road trip so i finally got a chance to get away from California gas and my short commute. i got on avg about 18 on the highway. occasionally higher. i had to smog my truck and fix all codes so i replaced the cat with a walker.

so the truck isn't as terrible as with my 6 mile commute but certainly not like new either. I need to redo the valve covers as they are leaking. i want to do a thorough clean of the intake and throttle body then. they are pretty gunked up. i think the pcv valve is responsible for spewing a lot of gunk into the intake for 330k miles. i eventually want to overhaul the a/c and evap canister as well. my goal is 1/2 million miles on this engine.

 

Good Job Nodnarb

The 3.4 liter Toyota motor is a bullet proof little beast if you take care of them. They will probably even out live the Homo Sapien species especially with the way this species is going.

You are not going to see your Tacoma get better than 18 MPG. Here is the trouble with the Toyota 3.4. Remember it was designed about 28 years ago so remember the time frame for the period it was designed when evaluating it. This engine was designed to directly compete with the Ford 4.0 liter V6, and the Chevrolet 4.3 liter V6. Obviously, it is a lot smaller engine than both of its competitors. Toyota needed an engine that made good torque and horsepower numbers to compete with their competition so they came up with the 3.4 liter V6. They were able to get good power out of the 3.4 by designing it with sophistication rather than size. For example, it has aluminum heads with double overhead camshafts which work two intake and two exhaust valves per cylinder.

Fuel consumption was not a priority when Toyota was at work designing the 3.4 liter V6, which is why the fuel consumption for this engine is pretty miserable for its size.

Hope that helps,
Paul

 

Or a smaller truck. Lol probably needs a tune up, filter, o2 sensors

 

2002 3.4 4x4 automatic, extended cab with a topper.

I was having bad gas mileage as well. Right around 11mpg in city driving and wasn't sure about highway mileage since I hadn't taken it on a long trip.

I replaced the pads and rotors, lubed the chassis, new shock/struts, lower ball joint, outer tie rod ends, got an alignment, cleaned the MAF sensor, replaced valve cover gaskets, replaced spark plug tube seals and PCV valve, new air filter, replaced rear diff fluid, synthetic oil, and only use top tier gas. I used an obscene amount of fuel injector and fuel system cleaners in this order:
1st tank: 2 cans of Chemtool B-12 fuel injector cleaner
2nd tank: Gumout All In One complete fuel system cleaner with PEA & a bottle of $.97 Super Tech fuel injector cleaner
3rd tank: Entire 32oz bottle of Lucas fuel injector cleaner w/ upper cylinder lubricant & 1/4 bottle of Marvel Mystery Oil

I took it on a 400+ mile roadtrip 2 weeks ago and got 19.4mpg with 95% interstate driving cruising at 74mph. With my most recent in town driving and fill up I am getting 16mpg and the temperature is drastically dropping to the point of a couple inches of snow.


I'd try all of the fuel injector cleaners listed above. Chemtool is an extremely aggressive detergent that puts Seafoam to shame. The PEA in Gumout is EXTREMELY effective in reducing carbon buildup. Lucas is a good injector cleaner as well and the upper cylinder lube should help. Also, check around and see if local shops will do a free alignment check. My toe was out of spec on my truck and that can cause a decrease in MPG. Make sure the brakes aren't dragging. And letting the vehicle warm up for a few minutes each morning will negatively affect MPG.