I am at a complete and total loss... of acceleration
 

Well I'm well over 2 grand in the hole now.

Been having ongoing issues with the 2000 LTd 4wd v6 I have where acceleration will intermittently cut out and idles very rough as well.

I bought this car to take across the country with my two dogs from our place in Atlanta which I'm supposed to leave tomorrow to our new home in WA state.

The acceleration issue was and I still is a must fix issue as I don't want to be turning left on a green (or some other scenario) and the acceleration cuts out right in time for me to get plowed into by a 16 wheeler.

I have changed/replaced;

TPS (Throttle Position sensor)
IAC (Idle Air Control)
MAF (Mass Airflow Sensor)
Gaskets and valve covers
Air Filter
Spark plugs
Ignition Coils
Spark Plug cords
Timing Belt (did water pump too just because)
Fuel Pump and fuel level (which did fix the guage)
Both O2 Sensors

and most recently and expensively the catalytic converter.

I thought that fixed it and I was good to go but low and behold it reared it's ugly head while driving tonight.

This is becoming very expensive, I think I might have bought a ruin, but I was thrown off by a good auto check and low miles.

At this point the only thing I can think of is a Tranny problem or Vacuum Leak. Ive been scouring the forums since getting this vehicle and i've run out of leads on to what may be causing this... Oh and that's not the only issue either... I get wicked vibration between 50 and 65 mph, but the acceleration issue takes precedence since it could literally become a life and death scenario.

Any ideas other than a dark corner and a .45?:wacko:

I think more info on the symptom would help. You said it "cuts out". So the RPM's drop back to idle and pushing gas pedal does nothing?

Or do the RPM's jump up with gas pedal but the truck doesn't move? Like movement cuts out?

Or maybe the engine tries to accelerate but slowly, like it's in third gear instead of first at take off?

Also, any similarities or consistencies of when it occurs? Cold? Hot? (Engine or weather) Turning? Directly from a stop? Trying to pass on the highway? When it rains or after washing it? Anything that you can think of that links the event helps to try and figure it out.

I can't gaurantee a fix via the Internet, but there no such thing as too much information.

Wicked vibration issues could be a bent rim which is easy to check. Also Lots of aftermarket rims dont center up properly on the hub. If they are A/M rims and not bent. I probably look into a good well spacer to get them centered on the hub probably.

Broken belts in tires on some occasions can give you a bad vibration.

Several other things can like a warped or bent rear drum. But that is mostly more noticeable when applying brakes.

Recapped tires will as well.

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See my post here regarding the acceleration issue. Andy Mod 2.0 with trac switch has been a work around for me.
Random hesitation when accelerating

Could possibly be the efi/fuel pump relays, ECM? If you've replaced everything else I think those would be close to whats left to cross off your list..Hope you get it sorted out I know the feeling.

Any codes set current or pending? When your lack of power occurs what happens to the rpms? Does it happen in a particular speed range?

2000 4Runners and older don't have VSC or TRAC so Andy Mod 2.0 doesn't apply to the OP

@AutomatiX You've prodded and probed of course, but I might suggest looking for a leak of some sort: It's also incredibly inexpensive to do especially if you have a can of brake cleaner.

With the truck running very strategical spray brake cleaner on various parts where air might escape or get sucked in (don't spray direct on sensors).

On our Hyundai I had a very similar set of symptoms as you have and I couldn't hear anything: a buddy had me do the exact thing I just explained: once I got to the intake manifold the car all of a sudden changed it's tone. In that case the manifold gasket had given up.

Good luck and welcome to WA! (When you get here)

(I tried to find a good video - nobody has one where they ACTUALLY find a vacuum leak)

I will play devils advocate here abit...

The parts that you have replaced....did you replace them with OEM parts? and if so, was it you that replaced them or a mechanic?

And yes you would have to be more specific on rough idle and acceleration problems. its not specific enough.

Have you looked at the Fuel Pressure Regulator? It's just a spring loaded check valve on the end if your fuel rail hooked to a vacuum line. Maybe the spring is sticking (or similar)?

Mine failed completely and was dumping fuel into the air intake through that vacuum line. I'd get random hesitations/stalling, hard starting, rough idling, etc. Standard low fuel pressure issues, but a bit random. Got worse over time, though. I was able to remove the air intake and slosh fuel around in it, so I knew the FPR was leaking. Maybe check that, or smell for fuel from the line?

I was (and still am) literally the only other person I've seen on this site whose FPR went bad so I took the risk with a used OEM one and it worked great, over 4 years ago. The new part is $$$ but I bought a used one off eBay for around $35.