The car in question is a 55 plate Vauxhall Vectra 1.9TD

The issue is for some reason it stopped revving when the turbo wasn't spooling. It'll slowly climb to 2,500RPM and then the turbo kicks in and it takes off. Though this wasn't the case for a while. I've had the car scanned (no fault codes), checked the plumbing for leaks and de-coked the EGR valve (though I am being told to just replace it for a new one).

Is there anything I am missing as what could cause the engine to not want to rev sans turbo assistance?

Thanks.

Is the air filter clogged?

Replace the nut behind the wheel.

Pull the turbo and see what happens.

Quote from lap traffic nz :

Is the air filter clogged?

It had a service 2 months ago, but I did clean the air filter as I am thinking it is air delivery that could be the issue as it seems to be running rich.

Quote from Forbin :

Replace the nut behind the wheel.

Pull the turbo and see what happens.

Thanks for that. And in the quest to find any leaky plumbing the turbo was disconnected from the inlet and it just revved slowly all the way through the range. The biggest problem as I'm not sure what is "normal" as it isn't my car. But I'd have thought even sans turbo it'd have more get up and go off boost than it does, like every other diesel I've driven.

Running on all cylinders? Check the plugs? Any clogged injectors? No fault codes would seem to make these unlikely, though.

It's a diesel, it doesn't have spark plugs.

Does it have a catalytic converter? This could be restricting flow of exhaust gas if blocked.

Done a compression and gas test? Diesels are run on compression (bad wording but its the only way i can think to put it) maybe the pressure is too low for good enough combustion to make the car have its original bhp, but the turbo bring it up to "normal" so it runs fine on the turbo?

After a phone call with a chap at the Vauxhall dealership they said it is most likley the DPS (I believe that is what he called it) is blocked, read: the exhaust is blocked, The best way to find out is to take it for a trashing (~3,000RPM for 30 minutes), which should dislodge the crap. Or at least, that is how they go about fixing the problem.

Thanks for the tips chaps.

in some vw's its called a DPF diesel particulate filter i think. when i light comes on you go for a 30minute blast on motorways

Ahhh, the good ol' DPF, the bane of people who buy diesels and don't understand that newer diesels don't like short / slow / stop,start driving.