Need some help figuring out my low power/mpg

[toverturf]

I have a 2000 Limited with 224k miles. Has 33" tires with 4.88 gears. Has bumpers, spare tire, RTT on top, winch. The problem (at least it seems like one to me) is that any tiny hill, when i'm going around 70mph, it'll start to lose speed and i'll either have to downshift to keep the speed i'm going or have the torque converter unlock. I usually cruise around 70-75 because if i'm going slower then that on the freeway it feels like it can barely keep that speed without keeping the torque converter unlocked, even on pretty much flat ground.

I also seem to be getting not the best MPG. Going around 70-75 i'm getting about 13mpg on average. I have a 1999 Limited that I drove before that had all the same mods on it and it definitely seemed to be getting better MPG and seemed to have the same power even though it was on 4.30 gears. One data point I have is I usually stop at the same gas station on the way to Moab. In the 1999 I would have about half a tank or just under when I got there. In the 2000 I had just above a 1/4 of a tank.

Here's the stuff i've replaced or checked.

• Spark plugs
• PCV valve
• Replaced any hoses the looked like could have a air leak
• New cat
• Air filter
• TPS
• Cleaned throttle body and MAF.
• Replaced injectors with motor west ones
• Checked coils (still OG) and spark plug wires. Both were in spec.
• Both O2 sensors
• Fuel filter
• New throttle cable
• Checked timing by pulling back the timing cover. Everything lined up.
• Fan clutch
• Checked brakes for brake drag and they are all fine.

None of this seemed to help that much. I've had no CEL the entire time and it seems to run great. I've thought maybe it could be the fuel pump but I haven't had any bad fuel pump symptoms. I'm not sure the best way to check the fuel pressure. I do want to do the fuel gauge TSB eventually so if I do that i'll probably just replace the pump at the same time. Maybe my coils are still an issue even though they checked out fine when cold?

Does anyone have any other ideas of what it could maybe be? Right now i'm kind of at a loss. Maybe i'm just going crazy and this is normal and not a issue? Maybe I just need to supercharge it haha.

 

[Grgg1978]

I have a 2000 Limited with 224k miles. Has 33" tires with 4.88 gears. Has bumpers, spare tire, RTT on top, winch. The problem (at least it seems like one to me) is that any tiny hill, when i'm going around 70mph, it'll start to lose speed and i'll either have to downshift to keep the speed i'm going or have the torque converter unlock. I usually cruise around 70-75 because if i'm going slower then that on the freeway it feels like it can barely keep that speed without keeping the torque converter unlocked, even on pretty much flat ground.

I also seem to be getting not the best MPG. Going around 70-75 i'm getting about 13mpg on average. I have a 1999 Limited that I drove before that had all the same mods on it and it definitely seemed to be getting better MPG and seemed to have the same power even though it was on 4.30 gears. One data point I have is I usually stop at the same gas station on the way to Moab. In the 1999 I would have about half a tank or just under when I got there. In the 2000 I had just above a 1/4 of a tank.

Here's the stuff i've replaced or checked.

• Spark plugs
• PCV valve
• Replaced any hoses the looked like could have a air leak
• New cat
• Air filter
• TPS
• Cleaned throttle body and MAF.
• Replaced injectors with motor west ones
• Checked coils (still OG) and spark plug wires. Both were in spec.
• Both O2 sensors
• Fuel filter
• New throttle cable
• Checked timing by pulling back the timing cover. Everything lined up.
• Fan clutch
• Checked brakes for brake drag and they are all fine.

None of this seemed to help that much. I've had no CEL the entire time and it seems to run great. I've thought maybe it could be the fuel pump but I haven't had any bad fuel pump symptoms. I'm not sure the best way to check the fuel pressure. I do want to do the fuel gauge TSB eventually so if I do that i'll probably just replace the pump at the same time. Maybe my coils are still an issue even though they checked out fine when cold?

Does anyone have any other ideas of what it could maybe be? Right now i'm kind of at a loss. Maybe i'm just going crazy and this is normal and not a issue? Maybe I just need to supercharge it haha.

So I had a power loss problem with my '99 about a year after replacing my cat. The issue ended up being that my cat got clogged somehow. Could have been that I had an exhaust leak that I didn't take care of by using the factory gaskets for the cat. Or it could have been other things that made it go bad. Either way see if you can take a look inside your cat or cats, mines federal emissions so I only have one, and see if they are starting to melt/clog.

 

[toverturf]

So I had a power loss problem with my '99 about a year after replacing my cat. The issue ended up being that my cat got clogged somehow. Could have been that I had an exhaust leak that I didn't take care of by using the factory gaskets for the cat. Or it could have been other things that made it go bad. Either way see if you can take a look inside your cat or cats, mines federal emissions so I only have one, and see if they are starting to melt/clog.

I just installed a new cat a few weeks ago so it's brand new. Unfortunately it didn't change much.

 

[phattyduck]

Is that 70-75mph adjusted for your tire size? 70-75 indicated will be 75-80mph actual if you aren't accounting for that. Even a stock rig at those speeds would be getting like 16mpg or less.

Also, 13mpg with an uncorrected speedo is actually 14mpg.

I have 4.88's, 32's and a supercharger and go 67-68mph (actual, with corrected speedo) - now I'm down in the 16-18mpg range most of the time. Pre supercharger it was more like 18-20. Slow down and enjoy the ride. I'm already near 2500rpm at that speed - so there's a limit to how far I want to push it on long trips.

I think you are underestimating how much a rooftop tent kills mileage and takes power away at speed.

-Charlie

PS. Early in my 4Runner's life it was a small tire 2WD - and would often get 24mpg if you kept it under 70 on the highway...

 

[toverturf]

Yea maybe I was just expecting to feel a bigger difference from the 4.88 gears. I'll keep it around actual 70mph as that's the speed limit around here and see what I get. I swear my 1999 got better MPG though with all the same stuff on it. Maybe i'm just misremembering though.