Volvo D6-435I-E WOT issue

Hoping one of the VOLVO guru's can help out.

Have a 2012 engine with 868 hours that won't go to wide-open-throttle (WOT) RPM's smoothly after a good 10 minute warm up at 1500-1800 RPM's. When the throttle advanced, is the engine will rev up to 3100 RPM's immediately, pause for a few seconds, then creep up to 3320 RPM's. This is repeated every time.

The engine guy replaced the turbo sensor that was giving a false boost reading of 45psi, when max is 30. After installing the new sensor, the turbo pressure reads correctly, but the WOT problem persists.

The turbo spins freely (mechanic did a manual/physical inspection-no fouling), verified fuel delivery is good (filters are clean), verified air filter not blocked. When he had computer hooked up, all readings appeared normal. At WOT, the computer indicates the engine is working at 100%. Compression check was average of 95% for the 6 cylinders.

Any ideas?

Holy cow!!! No Volvo experts weighing in on this? Yikes!!! I must have the "unicorn" problem. . . LOL

Hi Cap'n R and thanks for the reply.

Single engine setup/Exhaust color neutral (clear), not black, not white.
No gauges. When engine guy had his computer hooked up, he indicated that fuel delivery wasn't a problem.
He appeared to be pretty though with his trouble shooting - and he mentioned that his conversation with other volvo tech's that the turbo pressure switch was the original problem, hence the change. The old one did have a compromised bulb on the sensor tip.

I'd say "yes". When the volvo tech was aboard, he told me to "slam" the throttle from "engaged idle" to WOT. There was a definite and short "turbo bark" when it engaged.

Ken,
Thanks for the tip. I'll pass on to engine guy

Nope: Boat hauled in May. Clean bottom/clean wheel

Roger fishing. But it's the idea the engine wasn't "stalling" on the acceleration before, and now it is.
But I'll look into the waste gate! Thanks.

Sorry for confusion.

When engine had "annual" done there was no "stalling". After about 4 months, the stalling (or pausing) problem suddenly developed. When first observed, the engine would pause at 3100 rpm's for about 8 to 10 minutes, before slowly advancing to 3320 rpm (almost like a "load" program on a SULZER slow-speed diesel on merchant ships), although the throttle position was full ahead.

After the replacement of the turbo sensor, the engine still pauses at 3100 rpms, but almost immediately advances to 3320 very slowly, like the SULZER load program. The time interval between 3100 and WOT is now about 2 minutes, maybe 3.

When the mechanic was aboard, I seem to recall he disconnected the airbox-hence no air restriction. But the fuel pressure? Yeah, that sounds interesting.

The Heat Exchanger, Intercooler, and oil cooler were all removed and cleaned in August 2017. Only 50 hours on engine since service (I'm embarrassed to say - I need to get out more. But since I'm now officially retired, I can!!LOL