P38 BMW Diesel Lumpy Tickover

The BMW diesel engine .on occasion. will not tickover smoothly when hot and needs a blip on the throttle to recover the rhythm. This is most inconsistent so I'm sure its not something as serious as the injector pump.The car runs and pulls fine.Done the basics like fitting a new fuel and air filters..and turning off the aircon in case it was putting a 'load' on the engine that wasn't being compensated for. This seems to be a fairly common problem from posts on another site but no-one seems to have provided the cure. I have spent some time browsing this site but can't find posts about this...any ideas please ? !

hello,
I would check the pump timing, remove the hot-start-fix relay if installed, first of all connect to a diagnostic comp. and see if the temp. sensor values (coolant&fuel) are ok; here you can adjust the tickover speed as well.
cheers, korkut

Before you do anything, can I ask whether you use supermarket fuel?

Regards Trevor2

mekon said:

The BMW diesel engine .on occasion. will not tickover smoothly when hot and needs a blip on the throttle to recover the rhythm. This is most inconsistent so I'm sure its not something as serious as the injector pump.The car runs and pulls fine.Done the basics like fitting a new fuel and air filters..and turning off the aircon in case it was putting a 'load' on the engine that wasn't being compensated for. This seems to be a fairly common problem from posts on another site but no-one seems to have provided the cure. I have spent some time browsing this site but can't find posts about this...any ideas please ? !

Click to expand...

Have you ever seen the MIL light come on for a few seconds when coming off the throttle after a drive?
when you re-apply the throttle, there is a 'dead' spot of lag for a second or two sometimes?

To answer a couple questions..
I have never noticed the MIL light coming on but will look out for it

No I don't use supermarket diesel I buy mine by the 25litre can full when I transit Luxembourg in the truck..although its hardly worth doing now as it's about 1.30 euros a litre !

I hate to be the bearer of bad news. I have spent nearly 2 years investigating this fault and changed everything standard that 'might' have cause it. I also have a Rovacom Lite diagnostic system that can view live data and that also showed no error codes. Now for the bad bit . . .if the fault clears on slight revving and if it only occurs when stopping when the engine is fully hot, it is very likely a faulty dual-mass flywheel. This is a poorly documented fault that only happens to the manual 2.5 DSE. The flywheel is manufactured in two parts and they are joined by a viscous type material that wears with time, resulting in free play between the two flywheel sections and 'wobble' on the crank position magnets, giving erratic data to the ECU. Blipping the throttle lightly stops the wobble. Land Rover seem to be deliberately keeping the problem very quiet, although a few dealers do know about it. A lot of manufacturers are now having problems with dual mass flywheels and some aftermarket companies have manufactured solid flywheel replacement kits (doesn't happen to the old type flywheels) - unfortunately I haven't found one that matches the P38. The other bad news is that the clutch should be replaced at the same time for technical reasons. Cost is high. Main dealer quoted me £1300+ VAT for the job. The parts are ERR5205 (Flywheel) £547.41 and STC50512 (Clutch) £196.41. The giveaway is your classic symptom of just touching the accelerator to clear it, which identifies this cause, if all else is well. One slight improvement can be made by lifting the tick-over speed from 750 to 800 but you need a Rovacom or similar to do that as it's an ECU adjustment. I know how frustrated you are feeling.

You could also check the EGR Valve (exhaust gas recirculation valve), which can 'soot up' and give symptoms similar to those you describe. I have seen posts on this point in the past - maybe worth a trawl back through.

I am aware of the EGR valve problem, but the 1999 2.5 DSE and I think earlier models did not have an EGR valve - I think they only started fitting it from 1999 onwards. (Thank goodness!). My son had to strip & clean the EGR valve on his BMW tourer, but the symptoms are slightly different - the classic 'touch the accelerator' to clear the lumpiness after stopping at a halt sign usually seems to be the dual-mass flywheel problem, but cleaning the EGR valve is certainly worth doing on a regular basis if you have one as it can drastically reduce performance when clogged up.

For thos interested in the dual-mass flywheel problem on the manual 2.5 DSE (Land Rover - please take note) here is a link to a faulty VW one on U-tube. You can see the problem clearly on it. Seems that they are generally bad news.
YouTube - GOOD VW TDI DMF

Second link to a really bad one YouTube - Bad VW TDI DMF

Oh dear, didn't want to read this after convincing myself it was the FIP !

I bought a 2nd hand (pre- enjoyed?!) pump from a 49k mileage write off and was about to fit it to-day after finally sourcing a sprocket puller at a sensible price.

I did check the EGR valve was opening and closing OK by taking the vacuum pump pipe off the modulator valve and putting it directly on the EGR diaphragm connector and feeling the valve open. I also ran the car for a while with the EGR valve disconnected but still had the same symptoms so have concluded the problem is elsewhere.

There is a forum here Land Rover Range Rover P38 - 1999 2.5TD Lumpy Tickover: Motoring Technical matters forum that has kinda convinced me it is the pump until I read your post rrdriver !

Couple of points though ..if it only happens on the manual DSE then ,sure, it makes sense it could well be the DMF.. (mine is a manual).. but why does it occur only when the engine is hot? .. also doesn't the sensor take its reading from the part of the DMF that is bolted to the crankshaft and not the 'moving' part ?

Just thinking out loud..If a gear is engaged and with the clutch just dragging it should have the effect of 'locking' the DMF to prove the problem..hmm

I am surprised that these diagnostic checks show no fault codes..I had mine checked by a local guy using, I think, Autologistic and that showed 'no faults' !

The reason it happens when hot is that it takes time for the whole engine & transmission assembly to become properly hot and then it affects the viscous material that binds the two parts of the DMF together. It doesn't happen simply when the engine has reached normal temperature - it takes extra time for everything else to get hot first. Once the DMF is acting up the magnet wobble causes the lumpy tick-over when you stop - it probably sets up some sort of resonance that stops when you touch the accelerator. Because there are no faulty sensors as such and it is not an EMS fault, the ECU doesn't log any faults. As far as the ECU is concerned it is all working o.k. Dakar cars Dakar Cars 4X4 Index recently changed one of these faulty DMF's for one of their clients and he reported to me that they could move the two flywheel sections freely on the old part. After the flywheel & clutch change the lumpy tick-over was gone! Pity that Land Rover doesn't have the morals to do something about this fault.

Finally went for it and changed my DMF and clutch in the P38 ! Trust me its hard work on the floor without a ramp or pit. I used an engine lift through the drivers door. There is a removable panel on the tunnel that allows access with the lift. Even so not a job for the faint hearted!

I bought all the parts from these people..

BuyPartsBy

I have posted a video on utube showing the play in the old DMF against the new one

YouTube - Dual Mass Flywheel Range Rover P38 DMF

Thanks for all the input ..especially rrdiver ! fingers crossed that the 'fault' is cured

just a quick one , did replacing the dmf work??
as you have probably guessed I have the same problem.
Cheers

rphtow said:

just a quick one , did replacing the dmf work??
as you have probably guessed I have the same problem.
Cheers

Click to expand...

The P38 is not alone, Dual Mass Flywheels are a big problem, loads of MK6 Transits with DMF failure. Normal fix on the Transit is to replace with a solid unit although it alleged by some that this leads to crankshaft failure.

I understand that it did not miss a beat after changing it! I am about to do mine this month but I have learnt from another member who changed his DMF and clutch on a flat surface by jacking the RR onto four ramps and making a bracket to adapt his hydraulic jack to the gearbox bracket. I have checked my own jack and it has a lift of 495 mm including the normal pad (which you remove). It will work with mine but I would be doubtful if a low lift jack would have enough lift. Have a look at member zzr1200 at http://www.landyzone.co.uk/lz/f10/p38-2-5-dse-clutch-change-61659-2.html which seems to be the way to go. Also buy some clutch roll pins and a mechanic friend also suggests changing the spigot bearing at the same time. Pity Land Rover were not honest enough to tell people about this problem.

yu can get them brackets on fleabay - I fink Trewy has got one - he mite tell ya where he got it from and how much.

Thanks Mad Hat Man - I'll have a look. If anyone can give me the exact link I'd appreciate it in case I don't find it. Save me making one.

probably doing mine in few weeks, I will video the highlights and stick them on youtube, should be fun, luckily I have the use of some ramps

Hi landy lovers... my dse has a rough idle...but only when the car is on the move ??... hot, cold.. it dont matter... clutch in or out.. as soon as i stop tickover is smooth again?? guts me... any one any ideas....???

Hi guys! This morning I am aching all over! Yesterday changed the Dual Mass Flywheel and clutch assembly on the P38 2.5 DSE. Made up a 220 mm high adapter bracket to fit the trolly jack to the gearbox bracket holes and put the car onto four ramps. Disconnected battery negative within 30 seconds of switching off ignition and left the key in the barrel - no sync was needed on reconnection. Started at 0800 hrs and didn't finish until midnight. Having a friend help made the job much easier as the gearbox/transmission is a big lump to manipulate back in. I have taken a short video clip of the old and new flywheels and will put it onto U-tube in due course. The old DMF (OEM part) was made by LUK as is the new one - they have the same part numbers, so the price saving through buying from a LUK distributor was around £200. (Stuff LR prices!) Anyway, having done it, I am glad to say that the old flywheel was definitely faulty with 4 times the free play of the new one along with sticking and now that the new one is fitted, the fault is completely gone! The car is a delight to drive once again and the strange mis-fire stutter when stopped with a hot engine is no longer there. I should add that this fault drove me around the bend for two years as various 'improvements' reduced the problem, including increasing tick-over speed and even making a small electronic circuit to modify the fuelling. In the end it kept coming back and has now been conclusively proven to be a faulty DMF.