i just recently put i new engine in my 97 T, it was out of a 02 taco. when i fist got the truck two years ago I got it all checked out and it was good to go the mechanic said.. well a month after i got it it threw a code from the o2 sensors so i replaced them with some bosches. it helps some it still has not thrown a code. when i drive on the interstate i have to floor it, the motor revs but the truck doesnt take off you can feel the truck getting power then loosing it again. almost like your on the gas then off the gas again. i just put a good motor in the truck had it compression tested and everything. i have tried spark plugs wires, coil packs, and gas additives. anyone got any ideas?

 

Replace the Bosch O2 sensors with Denso. These Toyota engines don't play nice with Bosch.

 

would that really cause all this? i get about 12 mpg

 

Yes it can, and might check with OBD2 reader for possible stored codes.

 

i cant believe that would do that. i thought maybe the cat was clogged and one mechanic told me it was my transmission.. but after two years of doing this i would of figured it would have burned out by now. it never threw a code with the bosch o2s.

 

I went ahead and got a magnaflow cat and some O2s from URD.. hopfully this will fix my problem.

 

I put a new cat on it and the correct O2's reset the ecu and drove it for about 50 miles. I could tell a differance, but nothing major. My sisters 01 xterra (4 cylinder) feels like it has tons more low end torque. I have to encourage it to go into overdrive by letting off the gas a little and if there is a hill... I'll loose 10 mph trying to go up it. If I'm pulling something it acts like it can't pull my 4 wheeler around. I know toyota didnt make this truck like this, no one would have bought it.

 

What size tires do you have on there? Stock size? Did you regear if you went to a bigger size? Do you have the stock pipe size fer yer exhaust or did you go bigger?

 

I have 33 12.50s everything is stock, it was a stock converter. Everything is stock, except the 01 taco motor.

 

When I bought the truck 2 years ago it had 235/75, I'm assuming stock size, the acceleration was poor and it did the same thing. I live in alabama so there really is not a steep hill.. It would down shift and go nowhere.. I thought that was just how the truck was until I drove an 02 taco with the 3.4 also. The deference was shocking, thats when I knew something was up. I assumed it was the actual motor and drove it until it broke a rod put a good used motor in it and the exact same result. The mechanic told me whatever it is is putting an extra strain in the motor and caused the other one to fail. So far it looks like its going to have a for sale sign on it.