The vehicle:
2012 Land Rover LR4 HSE (can't imagine the trim matters), 115k Miles, V8, 5.0L

The issue:
There's an acceleration issue when the engine is in low RPMs; if I can get it to drop a gear, demand a higher RPM, I get acceleration that reminds me of the sizable engine. It leaves the line pretty well, regardless of throttle position, but in the 2nd and 3rd gears, the vehicle has a dramatic reduction in acceleration intensity until approximately 3500 RPM, at which point the vehicle lunges forward and exhibits the power you'd expect. It is more noticeable in the lower gears, but it has the same behavior at highway speeds, acceleration is almost nonexistent unless the throttle position demands a gear drop, which yields higher RPMs, and consequentially an exciting acceleration.

There are no codes; not on my at-home OBDII scanner, not with the local European Auto Mechanic, and none of the metrics jump out at them.

What's been done:
Cleaned the throttle body, rebuilt the transmission and replaced the transmission control module along with the torque converter (plus a few unrelated worn transmission components).

The result:
There's no longer any hunting in the tachometer, but the sluggish acceleration at RPMs < 3500 is unchanged. More smooth, sure. But the chief complaint exists.

 

Also:
There are no audible, tactile or computer registered misfires in any of the cylinders.

 

Have you checked fuel trims. I’d be thinking fuel pump (either high pressure or low pressure), or fuel rail pressure regulator. Strange no misfires, but still worth checking.

 

You said it so I'll check it but acceleration is spot on at and above 3500 RPMs in all gears so it doesn't read fuel pump, delivery or regulation to me. Still though, I'm taking all advise so tomorrow morning it'll get a check.

 

yeah, i agree with that - weak fuel pump should cause more problems at higher rpm, but still hoping fuel trims might give you some clue as to what’s going on.

 

I have exactly the same symptons on LR4. New injectors. New PCVs. 2nd hand throttle body. No codes are thrown. Did you ever solve your problem?

 

Issue solved. I replaced both high pressure fuel pumps and that solved the problem. The problem never got any worse, never threw a code, fuel pressures all measured in range but there was some weird behavior in the numbers when cold starting the truck so I decided the pumps weren't altogether that expensive, I'll give it a shot. 2 hrs of work, solved a problem (2) mechanics who "specialize" in land rovers told me was undiagnosable w/o a code. It was everyone's first guess here. Much appreciation.

 

So anyone looking at this gets the correct picture of what was happening, I was mistaken when I posted this response. The problem existed when accelerating in all gears between 2000 - 4000 RPMs. It was just less noticeable at higher speeds because I'd depress the throttle enough to drop gears, forcing higher RPMs and better acceleration. But sure enough, throttle down just a little bit and I got almost no acceleration out of the engine.

 

Solved it. It was one, or both, of the high pressure fuel pumps. I replaced both. Problem completely solved.

 

Going to try both fuel pumps this coming week. I hope I have the same results that you had!