So I have a 1992 4 runner 31x10.5 22re 275km stock as far as I know. The problem is that sometimes I have very little power until it hits 3500 in first and second and then it kicks in. So the short version is that I took it to the camp last fall and I abused it more than I should have. the next day All the problems sarted and every time I fixed one the next went in this order calipers, Idler arm, pads, rotors, afm, cap, rotor, plugs, wires, air filter, Valve adjustment(sounds like a diesel now), exhaust (after o2 sensor to muffler), spindle bearing flange(back of hub) then I tested the TPS and it failed the sweep test horribly but I had one from my mr2 lying around which passed and bolted up fine.
Before all this I was getting 18mpg for the first year then around 10 after the camp and now close to 13 after the repairs. Timing is dead on. The only way I can describe it is feels like turbo lag until 3500 and then it kicks and pulls hard. always at 3500 no matter what. I always run 100% synthetic oil and have never had to add even a little , as well the coolant is always fine. No codes either.

 

it feels as if the timing is off until it hits 3500 and feels ok after 3rd gear.

 

Sounds like it is running rich to me because it sounds like a diesel. When the flapper in my air flow meter got stuck it sounded and acted similar to what you are describing. Just a guess but it is worth checking.
Also in my sig is a link to factory service manuals.

 

The exhaust smells like pure gas at times

 

Replace the o2 sensor and see what happens

 

+1 on the o2 sensor.

 

my truck is doing the same thing and its driving me crazy everyone says check the o2 sensor but what if you have no cat or 02 sensor?

 

Well if you have no O2 sensor what are you using to send feedback to the ECU

 

i geuss nothing lol there is no cat or res the wire is hanging under the truck but there nothing to plug it into bin like that for over a year is there another o2 sensor

 

i have seen electrical ground failure, which causes unusual symptoms. My tail light wiring harness has been the culprate! Causes poor fuel pressure to the fuel pump. As the grounds grow more ohms, the positive wires suffer from heat build-up. This translates to OVERALL poor ground and will reek havoc on the rest of the system. the smaller circuits/further away from the power source are compromised, as well as sensitive electronics

 

When my TPS was out, I had fuel in the exhaust and the same delayed power, tho it seemed to kick in a bit lower than 3500. Anyway, is it possible the TPS you used isn't a straight swap?

 

sorry for not posting my solution. It turned out to be two things. The first was that there was a leak in the exhaust by the o2 sensor, which i patched and got a jump to 16mpg. Then I bought an Denso o2 sensor from sparkplugs.com and put that in. and the hesitation problem stopped, until the next week when that part of the exhaust finally broke. So I had a new one installed and the o2 sensor placed in that and my mpg jumped to 21 combined and that is with 31 x 10.5.