I have a 97 4runner with a 3.4, it has 169000 miles. On hard accleration it will hesitate and jurk at first, then barly pull through the powerband until it reaches 4500 to 5000, then it will pull like it should. Also sometimes under a slight load increase(like going up a slight incline) it will auctually buck. It will not throw a code...Toyota had it for a week...no answers. I have replaced; timing belt, tps, mass air flow, fuel pressure reg, plugs, wires, fuel filter,and it has a K&N air filter...HELP PLEASE!!!

 

Check your fuel pressure. Your fuel pump may be going out or the pickup screen is clogged. It sounds like you are running out of fuel under load.

 

Thanks, I'll try that and keep you posted

 

I agree you should check the fuel pressure by tapping into the injector rails.

Few questions:

When did this start?

Was it right after anything was replaced or you had work done?

Who did all the work on the truck?

Did you use all OEM parts?

 

been over a year, it has never been right, all toyota parts, dealer or myself and I always reset the computer..Thanks

Rusty

 

On my old mustang, the throttle position sensor also created problems like this. It is basically a potentiometer, and when the contacts get worn/dirty then it sends a distorted signal back to the computer. Mass airflow sensors also can be somewhat problematic.
I don't think it would pull hard in the higher rpms when it has problems picking fuel, would it?

 

that is what I thought before, i have already replaced both the tps and the mass air flow....

 

Thanks All....I had a bad fuel pump!!!! I am purring like a kitten(AT ALL SPEEDS!!!)