Add some injector cleaner to the fuel, at maximum recommended dosage - if the injectors are gummed up this'll clean it.

Pretty simple technology on the 1.9 pd - most don't have a DPF but there are some approaching 2010

A common fail is the vacuum/electric system that operates EGR, turbo variable vanes and anti shudder for turn off - but this does vary between models of car and engine codes.

Another common fault that doesn't always show up as a code with the 1.9pd is a failing injector wiring loom within the head. It sits in hot oil and is a well known problem.

It does sound like you've bought some one else's problem though.

What car is it and what engine code does it have?

Edited by Big John on 31/12/2021 at 21:22

Before you delve right in and overthink everything just remember this. A diesel engine needs the following four things to run. If it doesn't run properly, or not at all, one or more of these four will be the problem. Check and eliminate each one so that you can examine the others in more detail.

1. A good supply of clean oxygenated air

2. Good compression on all cylinders

3. A clear and unrestricted exhaust

4. A good supply of fuel at the correct time.

Start with no.1. Check the whole air intake to make sure it's clean, unrestricted and that the EGR valve isn't stuck open.

Check no.3 by dropping the front pipe and starting the engine. Bear in mind here you might annoy your neighbours.

No's 2 & 4 won't be as easy for you to check out unless you have the right equipment, but you may not need to go here if you find a problem with no.1 or no.3.