Bad Hesitation around 2500rpm

My truck is a 2007 CC TRD 4x4 V6 auto with 319,000 miles. Quite a few offroad miles and towing miles. It has a bad hesitation under moderate acceleration around 2500rpm, but once it gets to around 2900rpm it doesn't happen (I assume this where the vvt changes over). It's only between say 2300 and 2900 rpm or somewhere close to that, give or take 100rpm.

No codes, in fact the truck has never thrown a code. Basically everything is original to the truck other than spark plugs, belts, water pump, and radiator as far as the engine. Change the oil every 4000 miles

Ideas?

 

Fuel filter/pump? (should be good for life, though you do have a ton of miles on.) Clean your throttle body maybe...

 

Throttle body has been cleaned several times and plugs have been changed but neither made a difference. I thought about fuel pump/filter but it only does it in that rpm range. I think it's got to be connected to the VVT since it does it right at the switchover point.

 

I'm gonna guess Crankshaft Position Sensor but I could be wrong.

 

How would I diagnose that for sure without a code?

 

You would have to test the resistance of the sensor with an electrical meter. You have to know the acceptable resistance values however. They usually would be found in a factory service manual.

 

The only problem I have with the vvt system theory is I think you should see a code if that was malfunctioning. Have you checked for codes? I believe some do not set off the check engine light.

 

Nothing shows up on a snap on scanner, but I haven't been to the dealer. It's my work truck and I'm usually gone the hours the dealer is open. They don't really have a good tech for diagnosing stuff on Saturdays either.

 

What about your catalytic converter. Could be getting plugged up by now. Is it original?

 

Check the codes anyway. There could be codes, but no check engine light.

 

Cat converter is original

I will try and get by the dealer to see if any codes show up

 

To help rule out the cat you could crawl under the truck in the morning and give it a good shake. If the honeycomb has broken then you should hear some rattling. It could still be clogged if you don't have any rattles but it is less likely to be a cat problem.

 

Check your spark plug wires.

I have had some only arc at certain rpms. I thought for sure it was a transmission problem. Shop checked it out said wires bad put on new and worked just fine.

Have someone rev to 2500 rpm while you look under the hood. Do it at night look and listen.

 

No vvt on our motors, or spark plug wires.

 

V6 has VV-Ti... just not "dual" VV-Ti like the FJ and 4-Runner

I might suspect that one of the VV-Ti triggers is clogged.
Top front of each head, under the intake manifold.

The VV-Ti system is oil-pressure-driven. If the actuators clog, they don't operate properly.

 

That's more along the lines of what I was thinking

 

any luck here? Dealer just spent a couple hours on mine to no avail. Hesitation starts around 2300 rpm.

 

It probably wouldn't hurt to have the valve clearances checked.

 

You could also do a leak down and/or compression test.

 

Found the problem? Mine is doing the same thing at about 1000rpm-1500rpm cant figure it out...no codes pop up.