I have a 97 taco with a 3.4L and i have had this issue once before. I read the forums but never saw an answer to a problem similar to mine. When i hit the gas the truck seems like it hits the rev limiter and will not pick up speed. Truck runs great at low RPM.

I initially noticed something was wrong when my check engine light (CEL) turned on, so i plugged in the scanner and got P0133, for 02 Circuit Slow response (bank 1, sensor 1). I unplugged the battery and my CEL turned off. Never came back on, but the problem was still there. I read the forums and changed out everything, cleaned everything, nothing. There are so many things it could be. I then changed the o2 sensor and nothing, same problem. Then i thought cat must be clogged and was just about to order a new cat, when i decided to run the truck with the o2 sensor out leaving an open hole. Trucked sounded like a damn top fuel dragster and i gave it hell. Put the o2 sensor back in and the truck ran fine for months. Then just today CEL turned on and same code, same everything. Disconnected battery, ran truck, same problem and light doesn't turn back on. What are ya'lls thoughts? CAT?

 

Did you check and clear the code per the fsm? If you don't have a copy of the fsm usually the local library will have a subscription to Mitchell on Demand or Alldata and you can use it at the library and print the pages that you need.

 

'Hit the gas' as in WOT? At what RPM does said behavior occur? Auto or manual?

What brand of O2 sensor did you put in? If it was Bosch.....well, these rigs don't like Bosch. Period.

How long have you owned this rig? Miles? Maintenance history?

 

I did not clear the code as the scanner i was using was nothing more than a O'Reilly's scanner. The code was cleared by disconnecting the battery.

Hit the gas as in pedal to the floor. It is most noticeable when you are attempting to pass or get up to speed quick while cruising down the road. Not sure what RPM as i do not have a tach, but i would guess 3-4K RPM. Truck is an automatic.

I do not recall exactly the o2 sensor in question as it was months ago, but i am pretty sure it was a Bosch as that i all anyone seemed to have.

I have had the truck since 03', 160K miles, regular maintenance. Truck has had no problems up until this year. In 9 years i have gone through two starters, water pump, one fuel injector, changed the plugs twice, changed valve cover gaskets, rotors, changed serpentine belt and timing belt. Put in a new fuel filter and cleaned the MAF. That is it in 9 years.

 

What spark plugs are you running? next time you get the code, have a real shop read it. They can tell you the exact conditions that triggered the fault. Rpm's, engine load, coolant temp etc.

 

What's "everything," exactly?

Toyota trucks often don't run any better with a new Bosch sensor than they did with a failing original. You need a Denso if you don't have one.

 

As others have stated, Toyotas and Bosch O2 sensors and plugs do not mix.

If you are bogging down, the kitty may be plugged or your TPS may be on its way out.

 

If all else fails check the crank sensor under the timing cover. It is magnetic and will picks up all meal pieces and make for a bad signal to the ecu for spark.

My 1998 4runner did the same thing ran great but would not go over 2000-2100 rpm….

 

Thanks everyone for the posts. A little update on what i have done. My plugs are all NGK and have always been so that is not the issue. If what everyone says is true about the Yotas not liking the Bosch sensors that would make sense as all you can run is NGK or Denso sparks plugs as well.

I took the upper bank o2 sensor off and checked the resistance and it was within spec. I then ran the truck with the o2 sensor off to see if it ran better by purposely making an exhaust leak. By doing this the exhaust could breath better thereby eliminating the clogged cat theory. Also if it was the cat the lower o2 sensor should have read on the scanner. The truck did not run any better and did the same thing. When i did this before, i plugged the old o2 sensor back in, because i didn't want to hear the leak, and the truck ran fine like it always had and the problem went away, until this recent relapse. When i did it again this time, the problem didn't go away.

After plugging the o2 sensor back in i checked to see if the voltage was in spec coming from the sensor while cold and hot. While cold it was within spec, but while hot it started spewing some strange voltages up and down, but never reached the 0.9 MV that it should. I ordered a new Denso O2 sensor that i will install today. I will post my results.

 

Well it is not my Upper o2 sensor. Truck does the same thing when a new Denso o2 sensor is installed. Next up is to check the MAF, TPS, and then crankshaft sensor. Also something else to note, the check engine light does not come on. I honestly have no idea what it could be.

 

I've seen the same problem on a 97 4runner with the 3.4 and it was the crank sensor.

 

Did yours show all of the same symptoms that i described?

 

the vehicle had no check engine light. it ran good up to about 3000 rpm and it felt like it was bouncing the rev limiter. I replaced it with a new crank sensor from napa for about $100 bucks all is good.

 

Well i changed out the crankshaft position sensor and the truck did the same thing. So i have definitely ruled out o2 sensor upper bank, cat, and crankshaft position sensor. Now i am trying checking out the TPS and checking for any intake leaks. This has gotten to be a real pain in the ass.

 

Here's two links about hitting the "limiter". One said they fixed it with a new ECU and the other said it was a loose crank/harmonic balancer bolt that allowed the timing to get slightly off.

http://www.toyota-4runner.org/3rd-ge...ummm-what.html
http://www.toyota-4runner.org/3rd-ge...-backfire.html

You need to confirm at what rpm this happens and make sure it happens at the same rpm every time. You could even try putting it in neutral and see if it happens then as well. Since you don't have a tach, get one of these...

http://www.harborfreight.com/digital...ter-66632.html

 

If all else fails check the crank sensor under the timing cover. It is magnetic and will picks up all meal pieces and make for a bad signal to the ecu for spark.

My 1998 4runner did the same thing ran great but would not go over 2000-2100 rpm….

 

You took off the front lower timing cover and changed or cleaned the sensor correct? and not the knock sensor on the block ?