E39 525tds 1997 with rough idle and shaky

[malle pietje]

Hey there!

My '97 525tds with over 300th km's has a rough and shaky idle on some occasions. When the engine is hot, it often starts to shake when I put it in neutral or use the clutch when heading to a stop. When I come to a stop, it disappears, or by adding a little gas. There is no lack in power and it's never with a cold engine.

The car has a full inspection history from 0 untill now, last two inspections (I and II) I have done myself using the TIS inspection manual.

I have looked for vacuum leaks, changed the dieselfilter once more, cleaned the AGR valve and read out the computer with my carsoft interface, no faults detected.

I am planning on checking the injectors and timing, but can't do it myself. So to save costs, does anybody have an idea what this could be?

Thanks a lot!

Frank

[malle pietje]

By the way, the idle speed doesnt reach below the standard idle of around 700rpm...

[marti5]

I would say possibly the camshaft sensor, even though carsoft didnt pick this up...it wouldnt as its not totally gone, ive heard of this before and it was the camshaft sensor failing at certain times/points especially when the engine is warm/hot....

[malle pietje]

Hi Marti,

thanks for your reaction! Does de camshaftsensor check what position it is in? Where can I find it? Can't find it in TIS....

[marti5]

Change of plan the TDS doesnt seem to have a camshaft sensor, I worked on a 530d which did although you have two temp sensors in the side of the head, Iknow one of these communicates with the ECU, so it maybe one of these thats playing up,but which one I dont know:
TDS
RealOEM.com BMW E39 525tds Cylinder Head Attached Parts

530d
RealOEM.com BMW E39 530d Cylinder head cover

When was the last clutch change as it seems strange it only does it when your coming to a stop in neutral.

[malle pietje]

Ok, so no camshaftsensor...

Those temperaturesensors, I suppose when these are faulty, it should show when reading the computer? How could they influence the idle?

I don't know when was the last clutchswitch, but i have the impression it's coming up because there is a slight shock while pulling up in 1st gear, when the engine is cold.

How would you connect the clutch with the idle?

Thanks for you help!

[MADDOUG]

Possible 'throttle potentiometer in the pump'.

The track wears and it loses the signal so the idle jumps around.

Should tick over at 750 warm.

Do a search with your symptoms on google etc for 'land rover discovery p38a ' these had the same engine and there is a wealth of info out there.

If it does turn out to be your pump pot then make some thing to hold the throttle pedal open a bit to avoid the lumpy idle.

[MADDOUG]

The AIR temperature sensor or IAT (in my case on my e34 caused misfire across the rev range,sensor was £7 new and fits in my inlet manifold).

Your e39 has a maf sensor which is a lot more expensive but dodgy maf will give more than a bad tick over and you can unplug it and the car will run default and run smoother albeit at reduced power if it is bad.

Two temps sensors in the cylinder head,one for the ecu and one for the temp gauge and I think the one nearest the front is for the ecu.

If it is the pot then the problem will occur when the tick over reaches a certain spot.

Lets say it is shaking about at tick over and then you put main beam on and the rear window demister and the fan on full,well this may be enough load on the engine for the ecu to raise the revs and then the pot has to move off the bad spot or it may induce worse tick over.

But when mine went at first there was a window of 100rpm that it would do it in.

Some days it would not do it and others it was constant,but raising revs would see it go away,the pot is like a needle on a record player.When it is worn it finds and then loses the signal hence the ecu gets conflicting data as to what revs to tick over at.

If you find the lights and fan etc make a difference to it then to pin point it to the pot you can try different grades of diesel.

Tesco diesel is rough so if you are using it then switch to say Bp and note the difference,the Bp gives more power for less pedal and this because of the 'more energy' in the fuel needs less throttle and hence pot position for given tick over.

I noticed this in mine when it went bad as I used veg oil and often biodiesel so my symptoms would come and go.

[malle pietje]

Thanks Maddoug, I'll go and have an look what diferences turing on lights etc bring to my idle speed. Didn't notice anything however.

These temp sensores, are they located under th preglowers?

[MADDOUG]

They sit beside them,link here to real oem parts drawings.

Your e39 (link below) only has two sensors in the head

RealOEM.com BMW E39 525tds Cylinder Head Attached Parts


Number 10 is classed as double temp switch so on your e39 it may/must do both the ecu signal and the dash guage,the other is for aircon equipped cars.

My e34 drawing shows 4 sensors although mine only has 3.

[malle pietje]

Thanks maddoug and marti,

i'll begin with changing the tempsensor, then see what's the result. Then the next step I think would be to let the injectors and pumptiming be checked. They tell me it is a very common cause for these kinds of complaints.

What do you think about this?

[malle pietje]

Well, this morning a Bosch diesel service has read out the computer and checked the timing of the pump. Injectors were no possibility according to him.

Conclusion, worn fuelpump, replacing with a new bosch pump incl labour € 1850 (1650 BP or 2750$).

First thing to do right now is check if this conclusion is the right one. Second, decide whether or not to change it and when. Third, find out if I really want a brand new pump instead of a revised or used one and see if I can do it myself.

Any tips or comments?

[malle pietje]

I checked the TIS for doing it myself, and conclude that it's not for me. To much special tools and to complicated. I called a company specialised in diesel engines, they told me it probably is indeed the pump, or maybe worn injectors. They could check it, but with replacing injectors, it would cost € 500.- Then, I still would need to check the pump. And checking is about 150euro's. If that's the problem, they could replace it with a revised one, for a total of € 1700,-.

I found some used ones on the internet, around € 350, but that's just delaying the problem.

Also, I've discussed with both people possible other solutions, but they however simply stated that all possible solutions had to be seeked around injetors and pump...

[MADDOUG]

I had my pump reconditioned by P.B.ASHER who are in Southampton.

I paid £500 and had a complete rebuild electrical and mechanical although you can have either and then it will cost only half that,or specific parts changed.

Don't waste money changing the injectors unless it is for a used set that are cheap enough to warrant a try,I did injectors on mine and they made no difference.

Now the pumps are coded to the ecu with 3 different numbers so you need the same number pump if buying used otherwise it will not work.

993 or 994 or 995 are the numbers and these are on the side of injector pump.

Second or third line down is a line of numbers that starts with '0406 and then another 8 numbers after that,you need the last 3 numbers on that line and they will be one of those mentioned above.

Make a new throttle stop at the foot pedal and bolt it to the floor and then fix it so you can raise the idle to avoid the rough running is one way around the problem.
Have a look at how the pedal connects to the throttle potentiometer and work something out,the throttle pot has a very strong return spring so it will need some work to make something strong enough but it will sort it out cheaply .

[malle pietje]

Thanks maddoug, that's something to think about.