Mpg / power issues

[generalcorrosion]

So I have a 99 4runner 5 spd 3.4:

Originally - bumper, sliders 4.10s 235/85/16 km2

Plenty of power and 18/20 mpg

Changed - 255/85/16 and 4.56s (manual hubs unlocked)

Mpg - 10/12 and seems gutless


I've also tried 5.29 rear diff and also got the same bad mpg


Things done to fix the problem:
-Changed iac/tps
-Cleaned maf
-Changed front O2 sensor
-Changed plugs to Ngk dual electrode
-no rattle from catalytic converter
-changed fuel filter

Scan gauge shows no codes



Now I'm trying to figure out my next step before I take it to a shop for diagnostic.

Things I'm thinking - maf going bad? Cat going bad? Fpr going bad? Throw wires at it?

Looks like it's running rich too


Any help or suggestions?

 

[wheelds]

what is the Load Range on both sets of tires?

and what was the period of time between changing the sets? i.e. did you drive 50k before changing your tires?

also what type of bumper? how much does it weigh?

235's?? new definition of pizza cutters. Were those CUV(crossover) 4ply tires?

If your new 255s are load range E (10 ply) theres a definite increase in weight, but need more info.

 

[generalcorrosion]

235/85/16 km2s - they are E
They had 3/4 tread life

Bumper was with both tires sizes / gear selection - badlands bumper

 

[jgue467]

More rubber turning more often

Tough to beat physics but you've got more rubber on the road (more surface = more friction = lower mps) AND you are turning them more often relative to your tranny output so again (more turns required by tranny to achieve 1 turn of wheels = less mpgs). Less mpgs + less mpgs = Even less mpgs. No matter what i do it adds up to less or more of less...

 

[MStudt]

Tough to beat physics but you've got more rubber on the road (more surface = more friction = lower mps) AND you are turning them more often relative to your tranny output so again (more turns required by tranny to achieve 1 turn of wheels = less mpgs). Less mpgs + less mpgs = Even less mpgs. No matter what i do it adds up to less or more of less...

Partly true here. This would be perfect if the OP had the original gearing still. Since the OP has regeared to 456's and 529's, that has changed. While your tranny output is going to be working extra turning 255/85/16 tire's with 410 gears. Stepping up in gears is going to reduce the output turns of the tranny. If you were to go down to 307's the tranny would be working even harder than it was with stock gears. Going to 456's or 529's will reduce the work the tranny needs to do.

Think of it like a bike. If you have a single chain ring, and an 8 speed cassette. You cold assume you tranny is the chain ring, and your cassette is the 456 or 529 gears. As the cassette changes gears, your chain ring (tranny) is going to do more or less work depending on the gear choice.

Also, sometime the MAS is beyond cleaning. changing your gears should have shown in increase in your MPG's. Even if it was only 1mpg, you should have noticed something.

 

[wheelds]

So I have a 99 4runner 5 spd 3.4:

Originally - bumper, sliders 4.10s 235/85/16 km2

Plenty of power and 18/20 mpg

Changed - 255/85/16 and 4.56s (manual hubs unlocked)

Mpg - 10/12 and seems gutless


I've also tried 5.29 rear diff and also got the same bad mpg


Things done to fix the problem:
-Changed iac/tps
-Cleaned maf
-Changed front O2 sensor
-Changed plugs to Ngk dual electrode
-no rattle from catalytic converter
-changed fuel filter

Scan gauge shows no codes



Now I'm trying to figure out my next step before I take it to a shop for diagnostic.

Things I'm thinking - maf going bad? Cat going bad? Fpr going bad? Throw wires at it?

Looks like it's running rich too


Any help or suggestions?

For example
3.31 axle ratio, the driveshaft turns 3 1/3rd times for every revolution of the rear wheel. With a 4.30 ratio, it turns 4 1/3rd times for every revolution of the rear wheel. The numerically higher gear ratio (in this case, 4.30) increases wheel torque and improves acceleration from low speeds

you would want the highest ratio (4.10 instead of 5.29) for improved fuel economy because you will not necessarily need the torque. However, if you are towing a 6,000-lb. trailer, you will need that extra torque to get the trailer moving, especially up steep grades (5.29 instead of stock 4.10s)

you should be looking at a gear ratio lower than 4.10 to increase your fuel mileage no? If you are rock crawling or using your rig for high torque low speed you would be more interested in 5.29s?

 

[generalcorrosion]

Ive run both 4.56 and 5.29 with 33s before.

Both had more power and both got around 16-18 mpg.

My concern is what is currently up.

 

[Srabai]

When you calculate your mpg's, do you factor in the tire size change? Just an idea. When I swapped from 265/70/16 to 265/75/16's my truck felt pretty gutless for a few days. With no tire change calculations, I went from high teens to low teens mpg wise. Did you notice an issue right after the tire change? Granted, changing up to 4.56 gears from 4.10 will use a bit more fuel if you do a lot of highway. How many miles are on it? A good set of OEM wires probably wouldn't hurt anything.

 

[generalcorrosion]

When you calculate your mpg's, do you factor in the tire size change? Just an idea. When I swapped from 265/70/16 to 265/75/16's my truck felt pretty gutless for a few days. With no tire change calculations, I went from high teens to low teens mpg wise. Did you notice an issue right after the tire change? Granted, changing up to 4.56 gears from 4.10 will use a bit more fuel if you do a lot of highway. How many miles are on it? A good set of OEM wires probably wouldn't hurt anything.

Yep calculated change, you can literally see the gas gauge go down once you start driving. 4.56 are more efficient with a larger tire size, fuel consumption isn't just based on rpm.


Well talked to my mechanic friend and it seems more and more my MAF might be going out.

Calculated load
2nd gear WOT - peaks at 71 (5000) tapers off at 67 at redline
3rd gear WOT - peaks at 70 (5000) tapes off at 67 at redline