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[andymp]

Hi. I have a 2.2 Dti which starts and runs perfectly, other than a small misfire, judder, flat spot type thing on overrun / light throttle pedal.
This always happens at around 1500 rpm and at 1/2 inch throttle pedal position. The management light isn't on, and the vacuum system seems all ok. Any suggestions would be greatly appreciated.

Thankyou in advance.

[andymp]

Anybody...   

[VXL V6]

How many miles has the car done and what brand of fuel are you using?

[andymp]

Its done 181,000 but the engine was changed at 176,000 for one that had done 54,000 miles, and i normally use either BP or shell diesel?

[fergy]

Suggest it could be a sticky EGR. Next time it happens check if the EML flashes on for a second . You may not notice, the light unless you are looking for it,  it happens so fast.
Easy to remove and clean. Located under the bulge in the black plastic trim on the rocker box (oops!.. cam cover). Factors can supply a suitable cleaner.

[andymp]

Thankyou Fergy, 

The eml light doesn't come on, but don't think it would unless the fault condition(s) were present for 5 seconds, or so?

I cleaned the EGR valve, it holds vacuum ok, and the spring return feels ok, but the outer edge where it should seal on the corresponding part of the inlet manifold was dirty?

I may, next time i'm out on my own try to make it judder for 5 seconds or so, to see what fault codes it throws...

Could a dying VP44 pump cause these symptoms?

[VXL V6]

Could a dying VP44 pump cause these symptoms?

Yes, but you won't really know until it completely dies and you'll then get a series of 1600 codes.

Found BP diesel to be completely shite in all honesty, we've run three different diesels and whenever they've run on BP diesel they have produced plenty of black smoke and loss of performance throughout the rev range. No doubt people will disagree with me but that's my experience.

[andymp]

Also, it coughs and misses about 10 or 15 seconds after starting up from cold, so I'm thinking the diesel filter housing is letting air in somewhere... this may be a contributing factor?

Could a dying VP44 pump cause these symptoms?

Yes, but you won't really know until it completely dies and you'll then get a series of 1600 codes.

Found BP diesel to be completely shite in all honesty, we've run three different diesels and whenever they've run on BP diesel they have produced plenty of black smoke and loss of performance throughout the rev range. No doubt people will disagree with me but that's my experience.

I shall try a different brand of diesel next time I fill up...

[VXL V6]

Also, it coughs and misses about 10 or 15 seconds after starting up from cold, so I'm thinking the diesel filter housing is letting air in somewhere... this may be a contributing factor?

Always worth checking all those things that get dismissed. 

I guess if your going to check it you may as well put a new filter in and drain any water off using the drain underneath. If you do change the filter it stands a better chance of starting if you change it with the engine warm / hot.

Incidently, you mention the engine has been changed previously, was this complete with the fuel pump and turbo?

[andymp]

No. The crank broke in half, so i got a bare engine and put the pump and turbo off the old engine onto the replacement (Y22 DTR) engine.

[Marks DTM Calib]

Air getting in the system is bad news.

The VP44 pumps are bulletproof but the power transistors in the piggyback electronics are cooled by the flow of diesel into the inlet, get air in the system and the cooling stops followed by cooking of the transistors.....this is the main cause of failure.

Fit a priming bulb to the system with non return valve in it to help things but check and fix where the air is getting in.

As for a hesitation on light throttle, this might be a sticky injector which is not cracking properly when a small quantity of diesel is injected, a good dose of injector cleaner may help plus some 2 stroke oil in every tank is no bad thing either.

[andymp]

A service is pencilled in for tomorrow. All filters plus engine mounts...
I'll vacuum test the fuel system too...

[andymp]

Which injector treatment do you favour?

[andymp]

It had a service yesterday, all filters and oil and engine mounts, and diesel magic in the filter, and now its barely noticeable...   

[andymp]

. . .  Also the turbo is making a dentists drill type noise. Wondering if that could be anything to do with it...