Last week I was on the expressway and went to pass and my 1998 4Runner wouldn't shift down to pass.I thought it was my tranny, because everytime it went to shift it would studder, first to second, second to third, and third to overdrive. My ECT power was on so I turned it off. The problem was gone, so I thought. It ran smooth, and shifted without hesitation, until I gave it alot of gas. Turns out that it is not my tranny. I was in the driveway , reving the motor and at 3000 RPM's my runner boggs out and will not get above the 3000 RPM's. It runs fine at all RPM's up to 2950, but at 3000 it like the motor has all life taken away. No service engine soon light has come on either. I changed both O2 sensors last year. I cleaned, than changed the Mass Air Flow sensor,put a new fuel filter and changed the plugs (NGK) and wires with in a week, it still runs the same. I am at a loss, can someone PLEASE HELP me and tell me whats wrong. I am going to lose my mind and I don't want to waste anymore money on stuff that is not broken. "Thank you in advance"

 

I Have a K&N and it is clean,with a deck plate mod & scliencer mod.

 

Check for loose vacuum lines, that would be your best bet. Also, check to make sure that your intake hose doesn't have any cracks or is loose somewhere.

 

No overheating, no coolant loss?
Warm up cycle normal? Will it rev normally above 3000 while cold?
Idle is 800rpm after warmup?

 

If your intake tract ducting is all solid (clamps tight, connectors have no holes,etc.) and all of your vac lines are good and in place, can you check your fuel pressure? Sounds like it is getting too much air or not enough fuel...

 

Why not simply pull the codes with an OBDII reader? That should tell you if there's a persistant or otherwise fault and give you something more concrete to go on. Readers for OBDII aren't too expensive at the parts stores.

You description makes it sound a bit like a limp-home mode; but I am not an expert in how those modes feel in Toyotas.

 

runs the same cold or warm, drives fine in city, as long as you don't give it gas to go over 2000rpm. no leaks water pump was changed, timinig belt changed, plugs wires changed cleaned mass air flow, both o2 sensors replaced last year service engine soon light has not come on. at a loss

 

just throwing this out there maybe the cat is plugged up ????

 

I had the same issue when I accidentally reversed my TB gasket. So, I am betting on a vacuum leak somewhere between the MAFS and the TB. If you have the ISR mod, make sure you are running the updated threaded cleanout plug. The caps simply don't cut it in the underhood temps and will warp.

In fact, why don't you put it back to stock and see what happens. Also, have a code reader hooked up and see if you have any stored codes. Autozone will pull them for free.

 

It started to run like this before I did the ISR mod, I do have the cleanout plug in. I took off my TPS and started my 4runner, and reved it up. It ran the exact same way with the TPS out as it did when it was in. I changed the sensor and took out the EFI fuse to reset the computer. It ran the same way.

 

did you ever find out the problem? My friend has a 2000 runner with the same symptoms and he already replaced a bunch of parts.