'08 D5 185bhp Ex Plod

[DionBullock]

Hi all, We've had our works car for about 18 months now and so far it's been a bumpy road in ownership! Shes a 2009 D5 euro4 manual with approx 130k on the clock.

The end of 2015 saw the demise of a cylinder head, a piston, valve seats and bearings etc... £3500 bill thank you very much Anyway, it was all repaired/replaced with a new genuine head and necessary parts. oh - it also had a new swirl flap acuator a few weeks after all this work was completed, along with a dpf and egr delete as the dpf wasn't regen'ing - All I can imagine is all the **** that the broken head was throwing down (oil/un-burnt fuel/soot etc) had baked onto the dpf causing it to go into limp mode. It was running fine up until early last week.

The last week I noticed it had a slightly lumpy idle, but felt fine when driven normally, boosted fine, average fuel consumption, no smoke (only on startup - is this normal?) etc... Regardless, I booked her in to the garage for some diagnostics.

Nothing visually - no split pipes etc. Also plugged into computer and found to my surprise, no faults recorded! He even took the car for a drive and did a live log which showed nothing unusual.

The only tiny blip that happened for a fraction of a second was the fuel pressure on idle was a bit low. They fitted a genuine volvo fuel filter to see if that would cure it, but doesn't seem to make any difference. SOMETIMES when driven slowly you get the feeling the engine sounds a bit agricultural compared to what a normal D5 sounds like.

It's one of those questions... "What can it be??"

I thought I'd ask the forum with it's wealth of knowledge on D5 units so I can suggest to the garage on what to look for. Things like;

Fuel pump - would a faulty one throw up a code? is there an in tank and external pump?

air flow meter - a faulty one "should" throw a code right?

Injectors - I'd have a loss of power if these were at fault? Code etc?

Fuel filter - changed already

Air filter - new early this year

Swirl flaps - new actuator early this year - whats the chance this has gone again so soon???

Pipes etc - all checked for splits etc

Honestly cant think of anything else?! Any suggestions is much appreciated!

[MercedesDriver]

I have no knowledge of diesel engines at all but if there are no errors recorded the only thing that comes to my mind is bad fuel. Many diesel members (from different forum) use only Shell Nitro Diesel.

[andyredz]

You've not mentioned egr? Has that been checked (or even better imo deleted from ecu and blanked

As for fuel type, my worst mpg was when I filled up with a premium fuel so won't be doing that again. Local Asda about £1.07, premium fuel about £1.30 per litre.

[DionBullock]

Yes egr was deleted at the same time as the dpf,

Shes always filled at my local Gulf station, never use supermarket stuff tbh