I'm stumped at what could be wrong with my 4runner. it's a 99 sr5 auto 4x4. I've been having this problem that's intermittent and seems to mostly happen going uphill. When I start up a hill at 10 miles per hour or so and hit the gas, it doesn't seem to want to shift. I will have the gas pedal all the way to the floor, but the rpm's will start at about 2k and will climb very, very slowly eventually reaching above 3k but not shifting. This is most noticable when trying to climb a sandy hill while wheeling. I will have it floored, but the tires will not spin very much. Once in a while I can feel it kick in and grab about halfway up a hill on the trail and I have power.

I first replaced the transmission. (it had other problems as well anyways). I did replace it with a used one (with 113,000 miles that I got from a local junkyard), but what are the odds that both transmissions had the exact same problem? I'm 100% sure that the fluid level in the tranny is correct. I've also replaced plugs, wires, coil packs, TPS, and cleaned the MAF sensor. Do you think it could be the computer? If anyone could shed some light on this problem I would greatly appreciate it.

Also, I have no codes and no CEL.

 

TPS was my guess, but you replaced that.

 

Mine does it too, it seems like the tranny is holding a gear too long, I never thought anything of it.

 

Check your O2 sensors, it could be running too rich so when you floor it it just bogs the engine down. Have you done the deckplate mod? If so, do you put the cap on when wheeling? If you do, I think that would affect it, since your ECU is accustomed to more airflow, when you put the cap in it will be running rich. An easy fix would be to drive to your wheeling site with the deckplate capped, so the ECU can adjust.

 

Seems like a fuel issue? Check the pump and the filter?

 

I do not have the deckplate mod. I went to check the 02 sensor and one of them was loose. The one before the cat was not loose, but the one after is. I know the 1st one is for air/fuel, but what does the other sensor do?

 

I believe that checks the exhaust gas temps and stuff to see if it's running too lean / rich.

 

Plugged up or melted catalytic converters will cause that too.

 

Thanks for the ideas. I'll try them out next free chance I get and I'll post my findings.

 

I've had that problem too. Turned out to be the TPS. Are you getting a CEL?

 

Keep me posted, I somtimes get the same issue.

Where in northern Michigan are you?