Greedy

I Seafomed about 4 months ago and have had bad mileage ever since. Before the treatment I got 240 miles before low gas light, since I have been getting about 200. This is what I have done to try and fix this and the results:

1. Pulled and Cleaned Plugs - No Change
2. Pulled and cleaned MAF - No Change
3. Pulled and Cleaned Both O2 Sensors - No Change
4. Replaced Plugs - Got pre-seafoam mileage (~240 miles) for 1 tank and then mileage went back to crap. Have since checked new plugs and they are clean.
5. Replaced front O2 sensor - No Change
6. Replaced PCV Valve - Got pre-seafoam mileage (~240 miles) for 1 tank and then mileage went back to ~200 miles.
7. Checked numerous times for any vacuum leaks - no dice.

Would apprecaite any feedback anybody has as I am about out of ideas. tHANKS!!

Ontario

My $0.02 (you may have already done these...)

- Tires - air pressure & alignment?
- Replace air filter?
- Injector clean/servicing?

kevin444

well you do have a supercharger.

FilthyRich

that is about the mileage I get now with the s/c and URD. I used to get better, but of well its a truck. I do get better than 200 miles per tank on the highway (stock gears)

MTL_4runner

That could even be the difference between summer and winter gas.
You have done most of the stuff people would recommend to remedy the situation.

Greedy

The alignment, air pressure and air filter are all good and I also cleaned the throttle body out when I changed the plugs. I know that I'm not going to get "good" mileage out of the truck but it's the sudden drop in mileage that is bothering me. What's really strange is how the mileage fluctuates so much. Could it simply be my gas gauge or fuel sending unit?

Greedy

I don't thnik we get winter gas up here in the Pacific NW.

MTL_4runner

How are you calculating gas mileage?
....the gauge and sender should have nothing to do with it.

Did you go to larger tires recently?

FilthyRich

Plus the factory gas gauge is just a guide, not an actual reading

bamachem

If I get 240 miles on a tank, then I'm pushing it. I usually get about 210 to 220 and the light will come on. That's mixed driving - about 70-80% highway. I end up at about 18mpg. My gas tank is also smaller than most thanks to low clearance w/ 265/75's and big rocks at Tellico last summer...

Mine dipped off a bit and it turned out to be a dirty MAF from the amsoil air filter oil. After I cleaned it w/ acetone, then contact cleaner and gave the TB a good scrub w/ TB cleaner, my mileage went up. Mine dipped down to 14.5 MPG at its lowest point.

MTL_4runner

http://pugetsoundcleancities.org/FuelBlends_Ethanol.htm

bamachem

don't forget that w/ larger tires, your odometer will be off as well. going from 265/75-16's to 275/70-16's you're about 6% off. If you started w/ smaller tires to begin with, then it's off even more.

also, how are you calculating your mileage? just going by the odometer for the miles per tank or are you actually figuring out your MILES PER GALLON?

you CANNOT get your mileage by saying that you're empty when the light came on (18 gallon tank) and you got 240 miles so you have bad mileage. To calculate it, you have to look at the gas pump and see how much you ACTUALLY put in. Divide the number of miles driven (as shown on your odometer) by the number of gallons shown on the pump, then multiply by 1.06 to correct for your larger tires.

my guess is that you've probally been experiencing winter gas. we have it in the south, why wouldn't you have it in the PNW?

Greedy

Thanks for all the replies and help. I have not changed anything to my truck except for the seafoam treatment. immediatley after that, my gas light began coming on at ~200 miles instead of the pre-seafoam ~240 miles. I changed the things lited above and ultimatley had no change. The thing that is confusing to me is that after i changed the plugs, i filled up and got 240 miles before the low gas light came on. Filled up again and only got ~200. So I changed the PCV Valve and had the exact same thing happen. This is with keeping everything else constant (driving conditions, time of year, mods to truck etc..) I can't figure out why when I replaced the plugs and pcv valve it seemed to have cured the problem, but then it comes back after one tank.

Ontario

Besides the changes in the mileage, have you noticed any change in the overall feel and performance of your truck?

I would fill up a few more times and see if it remains the same (200 mpg), improves or worsens. It may be something, it may be nothing... My mpg tends to fluctuate abit from tank to tank - something as simple as running the heat can make a difference for my mileage.

bamachem

just curious, but did you put seafoam in your tank to clean your injectors or did you just suck it into the pcv hose? if you did put it in your tank, did you change the fuel filter after running the seafoam out?

i got better results MPG-wise after cleaning the injectors - but the engine ran smoother after doing the intake via the pcv hose...

Greedy

I actually did both - through the PCV hose and in the fuel tank. blew all kinds of smoke. The only thing I have not replaced is the fuel filter. Think I may try that as it is only about $30.00 or so. Did you change your filter after the seafoam and if so did it make a difference??

bamachem

yeah, i changed the filter. i don't know if it made much of a difference in itself, but as a whole, after changing the plugs, pcv, O2 sensor, and cleaning the intake, injectors, TB, and MAF, i went from about 16MPG to a recent high of 19.9MPG. that's w/ a SC and 285 MT/R's on stock 4.10 gears. I usually get about 18.5MPG.