Hi,
two months ago I got same problem-at high rpm(120 km/h on 2wd or 80-90km/h on 4wd) check engine light came up and I slow down about 20 km/h. I changed air filter, valves, cables, oils-nothing worked.
Then I made

1. http://www.4x4wire.com/toyota/mainte...a_4runner_30k/
Cleaning the Throttle Body……
and

2. http://www.4x4wire.com/toyota/minutemod/afm/
Adjusting the Air Flow Meter

and
problem gone!

 

They were able to clear the code for me,and its been ok after driving about 100 miles since. So far I checked the airfilter which was fine. Thanks again for the great info and fast response.
Don

 

A quick side note...

That link's a little off, the document is actually at:

http://www.4x4wire.com/toyota/minutemods/afm/
(note the "S" in "minutemods")

 

Hey, guys. I was on my way home from Denver today which is about a 45 mile drive and about 15 miles out my check engine light came on. Now that I got home I checked the fault codes and I have a 21 and a 51. I had one before I believe it was the 51 because if I remember right that could be the Throttle Body Position Sensor?!
If anyone can tell me what the codes mean and how to fix? I did look up the codes one says signal switch the other says O2 sensor.
And if those are correct. can someone tell me how to check the O2 sensors to know which one I have to replace as they are very pricey

TIA
alil2cul4u