Loss of power when accelerating
 

First off let me say what a great sight this is i had no idea there was something like this out there WOW!!! Alot of very good info and input as well as alot of very nice looking runners.anyway i have a 2000 limited 4x4 85,000 miles on it having alot of problems with acceleration when i step on the gas more than a 1/4 of the way down the thing falls flat on its face doesnt matter what speed i'm traveling at or if i'm in park has been doing this for a while now. I just replaced air filter & plugs also cleaned the MAF and still same problem.. any ideas on what it might be..thanks for taking a look.

Loss of power
 

I have a 2000 limeted 4runner with 85000 miles on her and when i step on the gas she falls flat on her face does'nt matter at what speed i'm at or if i'm parked same result. I did however cleaned the MAF and put new plugs in and air filter same thing still no power when give it more than half the throttle. Otherwise it rives just fine starts up great everthing else is working great. Getting ready to lift it 2.5" and put some bigger tires on so i would like to have the power for the bigger tires.

Any codes? Possibly a clogged catalytic convertor....

Thanks for respnding. Dont have any codes yet gonna go get them checked later today. you think it might be a cloged cat? I guess it could be. But do you think it could clog with only 85000 miles on it?

There's no mileage limit on the cat. The catalyst is a ceramic type honeycomb shape that can easily break apart and clog the output.

Again, this is only a theory and carries no guarantees that it is correct.

I had them check the check engine light for codes today it came up as p0171 system to lean bank #1 not sure what that means any idea's?

http://www.obd-codes.com/p0171

I would guess by that code, that you need to replace the mass air flow sensor...

Thats what I was kind of thinking I cleaned it first really good but made no difference I picked up a new fuel filter lastnight and I'm going to go get a new MAF put those on tonight if I can. But i will keep you posted. Thanks for all your help sometimes when you have a hunch but just not sure it's nice to have someone else's opion too.

IT WORKED I went and picked up a MAF sensor swaped the old one out . put put the new one in turned it over. it started right up better than it used to and reved up quick and smoothly with no hesitation at all.. Thanks for all your input Jeremy much apreciated.

No problem. Glad you got it worked out!

I am having the same problem, however I used a manual to check the MAF, and it checked just like the manual said it should. DO you think this could still be the problem? I would love getting this thing fixed, be glad you got it fixed while it was still running. mine has gotten so bad it wont move....

I would try a new MAF I cleaned mine i never had it checked though but i kept thinking that it was something else because i cleaned mine and it would still run fine just no ppower when i stepped on it. but as soon as i put the new one on it took right off all the power was back and it started alot better too.

If it is not the MAF, and you have replaced the plugs, check you coils to the plugs, ...., you could be misfiring on a cylinder from a bad coil wire.

Along these same lines, my son has a 2001 4runner which runs great until the engine heats up a little. (90 minutes into the drive maybe during winter or maybe 30 minutes into an errand in the summer) Then after being stopped for a traffic light, he presses on the accelerator and there's nothing there. (as other guy described "falls flat on its face") If you hold the accelerator down it eventually starts taking off at its own pace. Or he could be on the freeway driving fine and he hits the pedal to pass, and nothing happens. If cruise control is set on 70, then it might drop to 55 all by itself. It is throwing no codes whatsoever, so every shop says, if it's throwing no codes, then we can't fix it. Colder weather, it almost always runs great but with warmer weather it acts up much sooner. So is it possible it could be the mass air flow sensor...?

Forgot to mention we have had the throttle body cleaned but this has done nothing.