2.5 DSE goes in safe mode at full acceleration

[Geert]

I have a 2.5 DSE 1997 Automatic. When pushing the pedal to the floor for full acceleration, the car goes immediately in safe mode. For the rest it drives perfectly normal, only when I reach the end of the pedal travel it becomes tacky for it goes in safe mode. I already changed the transmission ECU, but this didn't help. Did anyone encounter the same problem?

[DaveSIIA]

Not had the problem, but could it be the potentiometer on the accelerator pedal has worn and is sending the wrong signal at max throttle?

[Geert]

I was thinking that also, and now it's confirmed by someone else. Thanks.

I've ordered a second hand pot.-meter and expect it to arrive this week. I will post an update once I've replaced it.

Another thing; Over here in Belgium a new Throttle Position Sensor costs about 350€ VAT included. That's an awfull disgusting lot of money for such a technically simple small device ... I found a real good supplier for second hand Land Rover parts at Roeselare in Belgium and if anyone is interested I can give the address.

[Geert]

I changed the TPS, without any results. It keeps going in safe mode at full acceleration. I'm becoming quite desperate now. At the local LR dealership they're also not able to find the fault. Heeeeeeeelp!

[fisha]

is there not 2 TPS's on the car though?

one on the pedal and another on the throttle body / whatever the cable pulls on on the engine for a diesel.

[David Sparkes]

I see you have changed the transmission ECU and the TPS.

It's little consolation, but I've yet to find any forum where members actually 'know' a great deal about the BMW diesel engine installation, in any car. I am onl;y looking at English language forums, if you can understand German you may have more success.

Did you change the gearbox ECU on the basis of information gained from somewhere, or was it a guess, like the TPS?

Incidentally, there is only one TPS, attached to the pedal. There is no mechanical throttle connection to the engine, as there is no butterfly to move.

If it were me I'd sit down for a serious session and read the Workshop manual on the BECM, looking for any comments relating to the engine or gearbox, and then I'd read the ETM about the Engine and the Gearbox. As a generalisation, an electronic fault is more often than not the ECU responding correctly to a faulty signal from a sensor. In this case I'd be looking at what happens when you need full power. The engine can respond by switiching off the HEVAC, for instance, and possibly other loads that take electrical energy, like the heated windows. The gearbox will obviously respond by looking at road and engine speeds, the current gear selection, etc. Coolant temperature may also play a part.

You haven't said that the engine is chipped, internally in the ordinary ECU, or with an external add-on box, so I 'm assuming it is a standard ECU.

I'm not pointing the finger at anything in particular, I'm just highlighting that you need to have a wide awareness of all the possibilities, some of which you can think of now, others that may only occur to you after reading a chance comment in one of the manuals.

I don't know what you are doing in the way of interrogating the ECUs, possibly you've been leaving that to the Dealer. Have they looked at the gearbox as well as the engine? Have they tried capturing live data, while the car is moving and you deliberately go into the fault condition?

The snag is they may not do this sort of thing very often, if at all, so be unaware of both what the tester can do, and lack the experience on how to interpret whatever results they get.

I'll just point out that the Rovacom can collect data in CSV format, and although it can take a bit of rearrangement to present the information 'nicely' in Excel, the results can be very useful, but interpretation skills will be required.

HTH

[geoffbeaumont]

Incidentally, there is only one TPS, attached to the pedal. There is no mechanical throttle connection to the engine, as there is no butterfly to move.

On most diesels, if there is a physical linkage it's to the injector pump. I'm not really a diesel person, but I wouldn't expect to find a physical linkage on any ECU controlled diesel?

[David Sparkes]

Geoff

You are correct in this example, which is what is important with this query. Personally I'm not going to be so bold as to say this is always the case with EVERY Diesel with an ECU involved in the fuelling control, but neither am I going to dispute your assertion :-)

I do regard this engine as an early example of Electronic fuel control, regarding it as only partially Electronic, as it is neccessary to time the high pressure pump mechanically, the electronics then doing the fine tuning.

Just my take, perhaps Bosch wouldn't agree with my 'half-electronic' designation :-)

The point here, in my mind at least, is that someone else may have introduced a half electronic system, and included a mechanical throttle cable.

Shrug - Don't know, so I leave the possibility open.

I was also responding to Fisha's suggestion that there might be a TPS on the engine, which is another theoretical possibility. You'll recall there is an engine mounted TPS on some versions of the petrol V8, which I thought might influence peoples thoughts.

Cheers.

[Porny]

I have a 2.5 DSE 1997 Automatic. When pushing the pedal to the floor for full acceleration, the car goes immediately in safe mode. For the rest it drives perfectly normal, only when I reach the end of the pedal travel it becomes tacky for it goes in safe mode. I already changed the transmission ECU, but this didn't help. Did anyone encounter the same problem?

Safemode??

Unless I'm very much mistaken if it's going into save mode, it will also log a fault on the engine ECU?? Is is safe mode, or is the engine hitting overboost and cutting the fuel? (this would also log a fault I think)

Is the engine warning light (MIL) coming on??

BMW diesels do suffer from problems with the fuel quantity actuator, which can cause hesitation at the top end - but usually also cause the MIL to come on. Poor starting can also be related to this.

Ian

[geoffbeaumont]

Geoff

You are correct in this example, which is what is important with this query. Personally I'm not going to be so bold as to say this is always the case with EVERY Diesel with an ECU involved in the fuelling control, but neither am I going to dispute your assertion :-)

I wouldn't be quite that bold either...there's always an exception to the rule...

I was also responding to Fisha's suggestion that there might be a TPS on the engine, which is another theoretical possibility. You'll recall there is an engine mounted TPS on some versions of the petrol V8, which I thought might influence peoples thoughts.

All EFI RV8s, so far as I'm aware - I'm not sure how you could build an effective fuel injection system for a petrol engine without this information (okay, doesn't have to be engine mounted - could be elsewhere on the linkage). Someone (Jez?) pointed out in the International forum recently that some Diahatsu diesels have throttles, which kind of proves the point above!

[Geert]

Ian,

It goes in safe mode without any warning, the MIL light doesn't come on, and there isn't any trouble code to be found in the ECU.

I think it's like David said before, a normal reaction of the ECU(s) to an abnormal input signal from one of the sensors. It just a question of finding out which sensor is responsible for this strange behaviour.

I've been to 2 different dealerships and neither one of them was capable of solving the problem. I know I shouldn't ask this, but if there's anyone out there with a spare copy of Testbook or Rovacom...

[fisha]

David's comments i think are right - there are a number of possibilities.

Having a browse of the RAVE manual, for the diesel it mentions the throttle sensor is critical in the general working of the system.

It also mentions that the system looks at driver demand ( from the TPS ) and the engine available power and if the driver demand is lower than whats available, it'll supply the power. However, if the driver demand exceeds the available power ( such as foot to the floor ) , the driver is over-ruled and the engine gives what it can and will limit itself to what it thinks is its maximum.

Which then leads you onto what the engine thinks its can give, and what it uses to limit itself.

Browsing the manual seems to show that the engine will look at the coolant temp, fuel temp and emissions ( plus probably a few others ). Personally i suspect that its down to:

Self limiting emissions somehow. The engine supposedly cuts back if it thinks the emissions are too high - dont know how it knows though?

EGR - supposedly the EGR system will cut off on full load . . . what would happen if it didn't?

As for the 2 TPS, yes, I was basing that on the V8 engine. There is one on the pedal and one on the throttle butterfly. The cruise control acts directly on the throttle butterfly and not the pedal so the ECU and gearbox need to know both the demand of the driver and the current position of the throttle body ( which may not necessarily be the same )

[Geert]

I have a model without EGR...

[fisha]

OK - no EGR.

Another thing which could be a place to look at is that fuel amount is partly controlled by a servo inside the fuel pump. This servo rotates a shaft which in turn mechanically controls fuel delivery. So i would agree with David's comments that is part electronic, part mechanical.

However, in order to know how far the shaft is rotated there is a potentiometer on the top of this shaft which provides feedback to the ECU on the rotation angle of that shaft. . . . . labelled here as 1 and 2:

Now the potentiometer feeds directly back into the main ECU ( on line 14 in the pic below ) along with fuel temp and something else....

And in reality, its identified as the following wire colours highlighted :

Now I'm just wondering whether when you put the foot right down, the ECU starts to open up the servo fully but that when it reaches full open, the potentiometer throws a duff signal. The manual states that erroroneous readings from this potentiometer can cause the engine to stall / not start. So maybe the potentiometer is worn out, or that the arm is swinging past the end of the pot or something similar.

I wonder if you would be able to see / tap into the readings of the potentiometer to see what happens when you floor it.

[David Sparkes]

I think Fisha is very probably on the right track, and my compliments to him for chasing it through.

My own enthusiasm is now at a lower level, but I can add information from days gone by.

Rovacom can store and record data from the Engine ECU, but only in the format and timescales that Bosch decreed when they wrote the ECU software. In practice this means there can be several seconds between records, so the output is not detailed enough for us. Neither will they record every parameter.

The next step is an oscilloscope, of which the PC based versions by Pico Technology are the most cost effective, if you don't have one on the shelf. Note that 'cost effective' doesn't mean cheap, you will still end up paying several hundred pounds.

Pulling back from such sophistication, an analogue meter could be used while the potentiometer is moved manually, but all you are looking for now is a smooth output displayed by the needle movement. Which level of sophistication we use, the problem is still that we don't know what the 'correct' results are, so nothing is clear cut. This is the shortage of information I referred to in a previous post. Even Rovacom error messages are 'unclear' as to what exactly is wrong; they mirror what Bosch have programmed. Specific detailed knowledge about the Bosch system is something the mechanic has to get from elsewhere.

Looking physically at the FIP we can see that, after removing the inlet manifold, it's easy to take off the top cover, and even to split it lower down, without disturbing the mechanical timing. So, if a supply of parts are to hand, it looks as though the FIP, and particularly the potentiometer / servo arrangement, could be changed in situ. I haven't been there, but when I floated the possibility I was told these parts were so expensive it was financially inadvisable to gamble on a DIY partial rebuild. Far better to buy an overhauled pump with guarantee (assuming the overhauler doesn't go out of business within the guarantee period, as mine did). If you can pick up a second hand FIP for a song then perhaps the gamble of swapping parts over makes more sense.

It's at this point I've stopped. I do have a problem with the fuelling, but it's not as severe as Geerts, thus I've put it on the back burner, living with the occasional lack of engine response. I've got three Diesel specialists to choose from. One doesn't want me around at all while they keep the car for a day to investigate, but assure me with complete confidence they can find the problem, although there was no verbal recognition of the symptoms when I explained them. The others didn't exude the same confidence, but at least one of them was willing to look, with me in attendance, but would I please do a flow check on the intank pump before making an appointment. Fair enough, and I'm technically capable of that, but I just haven't stirred my bones. The third, mmmm, big, expensive, they say they are capable, but I'm just not sure.

Geert, I'm not sure how much help all that was, but it's as far as I can go.

Oh, you asked " if there's anyone out there with a spare copy of Testbook or Rovacom...".

Both use Hardware as well as software, so a 'spare copy' doesn't come into it.

I'm no longer in regular touch with the Forum (... my enthusiasm at a low level ...) but there were Europeans on the Rangerover.net 4.0/4.6 forum. Whether there's a Rovacom owner, with the diesel module software in Belgium who would show an interest, I don't know.

I couldn't resist searching:

Gavin Short is a regular poster and is at Tervuren, Belgium, but I think he's petrol.

http://www.rangerovers.net/forum/viewtopic...um+diesel#17719 talks about Kempower in Belguim as BMW specialists, and the thread contributor VogueSE shows his location as Belgium.

Stevemfr is in Strasbourg, France. He appears to have a diesel, and a Rovacom.

HTH.

[Geert]

It took me some time, but I finally solved the problem. The most obvious was that the ECU misinterpreted a signal from a defective sensor. After studying the RAVE manual for several nights and carefully observing what went wrong and when, I came to the conclusion that it could only be the MAP sensor. It could be possible that it was just not defective enough to trigger a trouble code. I checked the ECU several times with a notebook and couldn't find any trouble codes, still the engine went in safe mode several times. It occured every time when the rpm was around 4000 and the pressure in the intake manifold was at its highest... To make a very long story short, I changed the MAP sensor (75€, 10min. work) and everything works perfect now.

Thanks anyway to you all for the tips!

Specially to David for his "Zen" approach, this helped me a lot: As a generalisation, an electronic fault is more often than not the ECU responding correctly to a faulty signal from a sensor.

[geoffbeaumont]

Nice to know it ended up a simple fix

These things frequently seem to be a lot harder to diagnose than to actually put right once you know the cause.

Could your problems be caused by the AFM as well, David, or have you already eliminated that?

[Hybrid_From_Hell]

So much for the dealers eh ?

Nige

[Abe]

Geert

try paddocks if you need anything I agree Belgian Dutch / german LR RR parts prices (why pay a middle man)

http://www.paddockspares.com

or

http://www.lrdirect.com

Ok paddocksthey have limited P38 inventory

furthermore regarding paddocks I find them great. order on a monday sitting at the door for wed in belgium

if you send them a e-mail with the part no they will do their best to source something

best wishes

&

Happy trails

Abe

[Geert]

I've ordered several spares at Rimmer Bros in UK. Perfect service and prices 60% lower compared to Belgium.

[Abe]

Thing with paddock is that with a order over GBP 50 the delivery is gratis

best wishes

&

Happy trails

Abe