I'm at a loss, amateur mechanic here.
2000 Tacoma 4x4 3.4L v6 - ~160,000 miles.

Running terrible. It idles ok and drives ~ OK at a constant RPM. As soon as I put any kind of load on it, it loses all power and just kinda chokes out (no backfire, doesn't die). Occasionally it runs rough at idle and will die.
It just has NO power under throttle, i can barely even manage driving in traffic. I have to feather the throttle up very slow and gently to get it up to driving speed. Once there it seems to maintain pretty well. Throwing error code P0171, Lean in bank one. I've cleaned the MAF, replaced O2 sensor in exhaust, replaced fuel filter and looked for leaks (anything obvious), etc.
It seems to me like it's fire or fuel, but I don't even know where to start. Any help or suggestions would be greatly appreciated.

 

Check your plugs, wires and cap. Maybe try and run some injector cleaner through the fuel system.

 

Did you clean the MAF with brake cleaner? if not, do so!
If the P0171 code persists, then replace the MAF sensor.
That is likely why your truck is driving so crappy.

 

Yeah, I cleaned it with break cleaner. But this is not a running a little rough and CE light is on. This is an oh my god it runs like crap (almost undriveable). Also, it only throws the code from bank 1. Shouldn't a MAF cause the code from bank 1 and 2?
Oh, and I'll check that distributer cap ASAP..

 

Ok, first, you have no distributor cap.....or distributor for that matter.

It sounds like that truck needs some basic maintenance badly. For all the stuff you replaced, did you use OEM stuff? You should be doing at least all the tune up stuff and see where that gets you.

You can find it al in here (5 pages worth):
http://www.4x4wire.com/toyota/mainte...30k/index.html

 

fpr or fuel pump maybe?

 

new fuel filter could help. It cant be a distributor cause it has coil pakcs and the ignitor should be good if its firing. Which 02 sensor did you replace pre or post cat. the bank 1 and that code could easily be the pre cat sensor. it sounds like you replaced it but did you replace both?

 

Only front O2 sensor would affect driveability so replacing the 2nd one is pointless without a code for it.

 

+1 on MAF. They sell MAF cleaner too

 

i would also check for vacuum leaks-do you hear any type of sucking noises from the intake area? unmetered air leaks will also cause lean codes,such as hoses off or torn ,pcv hose

 

Did you just buy this truck? How long has it been running like this?
With that many miles, and what you are describing, I'd do a compression test.
You can buy a gauge for $25 or so. Years ago I had a Buick V6 (blech),
and I threw everything at it, cleaners, filters, checked everything. (It had burnt exhaust valves) After $200 in "fixes" and running it around trying to determine the problem, I blew the whole damn engine, when I could have probably gotten away with a valve job (they were easier back then). The moral to my story is try to check the most serious possibilities first, if it is something serious, ya don't wanna push it too hard...
My 2 cents...


Chuck

 

didn't really say what the plugs looked like replace them with NGK or ND
and change the fuel filter if for nothing else for preventative maintenance clean the maf and check for vaccuum leaks then gets the codes read at autozone or where ever checks for free and get back to us

 

I always say it, but, I think its worth checking into. Try cleaning the Idle Air Control, located right beneath the throttle body. I noticed better acceleration, start up, and obviously idle. There were times when I would give it gas, and it would want to choke and die. Cleaning this area really improved all aspects of the running engine. Its very simple and all you need is brake cleaner or some Carb cleaner.

 

And don't forget to clear the codes

 

Thanks for all the input everyone, I'll keep you posted.


And I do know that there is no distributor, I thought it was funny so i was throwing back a little sarcasm. I'm going to go replace the spark plugs on my diesel now.

 

if it is throwing a lean code check for vacuum leaks. could be a leaking or cracked intake manifold. with the engine running take some carb cleaner with the straw on it and spray around the engine and vacuum lines. if u hit a spot and the engine idles up then u have found the area where your vacuum leak may be. and check the STFT and LTFT to see if the computer is making the cylinder lean or not. or if it is lacking fuel.

 

If you are having problems with the motor dying/stumbling when you put a load on it/accelerate then make sure you check the air tube from the airbox to the throttle body if you have that system , the air tube can crack and you won't see it or hear it but when motor torques it will open and cause a lean condition for sure , if you have that system then just idle motor and squeeze the tube thoroughly and if there is a crack it will seriously stumble or die

 

Again, thank you all for your input and suggestions.

I took it to my buddy's shop and plugged it in. Turns out it was the TPS (throttle position sensor), so if you are having trouble like this it is a good place to start.

 

Cool , yeah controls are generally the culprit