"Stuck" throttle only in 4th gear?

I have a used 2008 Tacoma Access Cab, 2.7l, 5spd manual, 4x4.

I appear to have an electronically sticky throttle, and only in 4th gear. It only happens when I am hard on the throttle.

Ex) If I am in 4th, going up a grade, after the hill crests, I push in the clutch/let off the gas and shift into 5th. The rpms (2500-3000) will hold steady until I engage the clutch, even if I hold down the clutch for several seconds.

Conversely, if I am using 4th gear going DOWN that same hill, when I depress the clutch, the RPMs will drop faster than I can shift into 5th.

This ONLY happens in 4th gear, and there is no ambiguity about it. Under the same circumstances in any other gear, the RPMs drop like a rock, but in 4th, they won't drop.

Any thoughts on the cause?

 

Yeah, my old 6spd did it slightly, and in every gear. For my 2012, if I left it, the rpms would settle down in a short time (1 or 2 seconds).

But with this one, it's just 4th gear, and they WON'T settle down. If it sticks, and you hold the clutch for 10 seconds, the RPMs are still up. If you let go of the clutch at that point, the truck will jerk forward.

I think whatever causes RPM hang has gone bad and needs to be replaced. Is that the ECU?

 

clean the throttle body, but sounds like the standard RPM hang... if you are in 4th giving her and speeds are up the ECU doesnt want to you to drop the clutch into 5th or 3rd with the engine at idle.

 

Yeah, I may try that. Maybe it's only too dirty for 4th?

I definitely understand the usual 'hang', but this is unreasonable. Since it's only in 4th, I thought it may be an electronic issue. We have some big hills in CO and it's only 159hp, so there are also times when I have it floored for a while in 3rd, and don't get the same 'hang'.

 

Tried, and it doesn't seem to have solved the issue.

 

My 2.7L 5 speed did exactly the same thing from brand new, same 4th-5th conditions. Dealer told me it was an emissions control issue, "They All Do That". You'll get used to it and shift accordingly.

 

That's what I thought, but quite annoying. The only adjustment I could make is setting an egg timer @ 45 seconds and leaving it in 4th until it dings.