My car performs great until the engine fully warms up, then it all goes horribly wrong. From cold, I do get a slight splutter and squeak which is a bit better with the ECU update but that isn't a main concern.
Sometimes, I can pull away from junctions and there's zero power, think of a pick-up truck being fitted with a 1.2 petrol, to give you some idea. The turbo doesn't spool at all (measuring 0 bar). I put my foot right down to the carpet and can't even get enough speed to get it into 4th gear. There's also a loud hum coming from the front of the car during this time, the same kind of hum you get when the DPF is regenerating, but I'd hope you'd still be able to drive the car whilst that is in progress.
Also, it simply cannot hold a steady idle at all. https://www.youtube.com/watch?v=hbXE5Ff6Wjs
Not my video but I do wonder if this is my car with it's previous owner as my cars mileage at this videos age seems to tally.
Say if i'm waiting at a set of traffic lights for example. Even after 5 seconds of coming to a stop, the rev counter bounces up and down and the entire car shudders. You put the slightest pressure on the throttle (say, to around 900 rpm) and the idle is petrol smooth!
Another issue is that the car develops a slight misfire/cough around 2000rpm, especially if I am cruising and then put my foot hard down.
I do take it on short trips occasionally but then I also take it out for italian tuneups wherever possible. The distance I drive to and from work should be sufficient for the car to warm thoroughly, But it's after the italian tuneups and changing the driving style back to a more cruising mode that it seems to be more noticeable.
The car is always running on BP Ultimate Diesel, but I have noticed it's been even worse since they have started using this "Active technology" branding, but it might just be a co-incidence.
So far, I have cleaned the MAF with a MAF cleaner, being careful not to touch the wires or any sensitive components. And then I refitted with new screw on type clamps which hold the maf so firm it doesn't move at all. It seems SLIGHTLY better since doing this. I'm also running BP Ultimate with "Active Technology" with BG244 which has been in there for about 90-100 miles.
I had a mobile guy come and give the car a carbon clean, which had very little effect, except from it responds to the throttle a bit better, and the fuel economy improved.
The car has also had a recent service with correct oil, all filters changed and a new cam-belt done at the same time.
Can anyone help?