TD4 - MIL lamp on overrun

Hello all, just got myself a 2002 Freelander TD4 project on e-bay. 131k but runs very well, has full history etc. The owner sold it because of a problem which he has spent £1,700 over 8 months trying to fix.

When driving it runs okay but then the MIL lamp comes on, it then runs rough at low (<1500) RPM and misfires on tickover with smoke and diesel smell from the exhaust. Turn it off and on again - it's fine.

What I have noticed in the day or so I've been driving it is that the MIL lamp comes on when you overrun the engine by slowing through the gears (i.e. drop into second and spin the engine up to 2,500 or more). With that in mind, I am now able to drive it carefully without the MIL lamp coming on at all.

Being TD4 all my usual OBD gear draws a blank - I know the answer is to get it on the correct gear and I will do that when I can find someone local to me who has the correct gear and I can trust.

But in the meantime, any suggestions would be welcome?

Many Thanks
Richard

Sounds like a tubo spin problem to me, but best to go through diagnostics first , iron out all the common things first, filters specially the fuel filter and the small vacuum air filter [at back of engine lhs and looks like a small old type fuel filter] fuel pmps ,2 on your motor , turbo inlet rubbers [small holes or not sealed] 3 on your motor and not forgetting the MAF do the dissconect check [go into search ]

Thanks for posting Ming. Having done a little more reading I am inclined to suspect the Inlet Manifold Pressure sensor - I'm just wondering if on overrun where is it subject to its lowest pressure it goes open or short circuit causing the ECU to assume it's dead and use a default value? Going to go through all the obvious stuff you suggested this weekend starting with the easy ones. Not sure what you mean by the turbo spin problems? Having searched I gather the MAF check is to disconnect it and see if the engine runs better/worse (or check it is connected in the first place).

Does anyone know a good garage in East Yorkshire with TD4 compatible diagnostics?

Cheers

]Sorry Tannaton was not clear on turbo spin and maybe incorrect wording [i'm nor from your world so bear wiff me] the tubo on the td4 is a moving vane type that move from the BP control solinoid that gets its signal from the ECM [ENGINE PHOOTER] at low revs vanes are nearly closed and open more with RPM . . .Nuff of that ,thing is they can get sticky and not function as they should , but as said sort out the easy bits first and if youve still got the problem then diagnostics [trouble with that is you need to have a open mind to a fault or not] oh and check out if they still do it the ELM program for a laptop for the td4. . . . .best oh luck Earthling

Ok I think I have now sorted it. After much reading of posts and books and on-line etc. I had narrowed it down (in my own mind anyway) to either the inlet manifold pressure sensor (boost) or the fuel pressure regulator. There was another symptom which I didn't include in my original post in that the car used to run on for a second or two after the ignition was switched off. I got myself another boost sensor as there was one for £10 on ebay, haven't been able to find anyone selling a fuel pressure reg separately as most people seem to consider it an integral part of the high pressure fuel pump.

Anyway, yesterday morning starting removing bits, first time I'd really worked on the Freeloader and the engine bay isn't as easy a place to work on as my 300Tdi Disco... First I took out the fuel pressure reg, it is held on to the back of the high pressure pump by two torx screws, to get reasonable access you have to remove the inlet manifold and a couple of coolant pipes. Whilst I was at it I also removed and checked the PCV filter which was ok.

Got the FPR off and it looks like this:






It looked spotlessly clean - if you look closely at it you can see how it works with a tapered needle in the tube that sticks into the pump itself. I tried connecting it to a 12v battery expecting to clear a click and see the needle move, but nothing. So I put a long socket over the tube to protect it and tapped it on the bench a few times hoping to release it but after 10 mins of messing about - still no movement or click. So I assumed that is seized and that I needed to order a new one, and put everything back as it was without changing the boost sensor.

Took the car out just to check it was still going and hey presto - feels like a different car! No MIL lamp on overrun, no run on after you turn it off, much smoother and feels noticeably more torque below 2000 rpm. So it was something to do with the FPR, if the problem re-occurs I will endeavour to get a replacement. I found another (old) post where someone had experienced similar symptoms, someone else suggested running a strong dose of injector clear through for a while, I'm going to do this anyway, can anyone recommend a good brand / dose of injector cleaner? I had previously tried Millers on my Disco.

So to finish the car all I need to do now is fix the thermostat, courtesy lights, electric windows (x3), sunroof, central locking, fit recon VCU and sort the knocking front suspension!

Big thanks to the forum.....

I would normally recommend an injector cleaner that would be added neat to the fuel filter, but that's a bit hard to do on the TD4 I gather.