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[unlucky alf]

Last year I had a problem with loss of power on a really hot day after a good run, Well today I drove to Sheffield for a hospital appointment & it happened again, not only was it very sluggish on pull away but when i put it in reverse the car would move backwards on tickover as it should but when i put my foot down on the gas pedal it made no difference, Its almost like the accelerator pedal had been disconnected with no rev increase at all, Once its cooled down for a while then its ok , So obviously its something thats getting too warm causing it but my question is what would be the probable cause to this?.,,,,Cheers.

[unlucky alf]

I forgot to mention that its a 2.5 diesel .

[TheBoy]

Any fault codes stored (being BMW, I'd bet my left gonad that no EML came on, even if there was a fault)

[freecall666]

could it be the ecu temperature sensor? or air intake sensor?

[Johnny English]

I'm not sure of using proper English word but fuel feeder fault gives similar signs in case of hot diesel engines. Excuse me if I misunderstood something.

[unlucky alf]

Youve got it TB ive got no codes & no lights, I didnt know that the ECU had a temperature sensor, Also mine being an older one it doesnt have the air intake sensor to my knowledge, Im curious about the fuel feeder suggestion, What exactly would control that & what is the cure?.

[Omegatoy]

Youve got it TB ive got no codes & no lights, I didnt know that the ECU had a temperature sensor, Also mine being an older one it doesnt have the air intake sensor to my knowledge, Im curious about the fuel feeder suggestion, What exactly would control that & what is the cure?.

fuel temp sensor in the pump, does it have hot start problems? if not think i would be looking at the fbw throttle system, maybe the pedal sender?
as it sounds like its not getting the signal at the pump?

[unlucky alf]

Youve got it TB ive got no codes & no lights, I didnt know that the ECU had a temperature sensor, Also mine being an older one it doesnt have the air intake sensor to my knowledge, Im curious about the fuel feeder suggestion, What exactly would control that & what is the cure?.

fuel temp sensor in the pump, does it have hot start problems? if not think i would be looking at the fbw throttle system, maybe the pedal sender?
as it sounds like its not getting the signal at the pump?

It seems fine starting up whether hot or cold, What you say about not getting the signal to the pump would fit, Although wouldnt it play up irrespective of temperature?, Like i say it only happens when its a hot day after a good run, Is the pedal sender serviceable by any chance or is it down to fitting a replacement one.

[freecall666]

An ecu temp sensor can completly fail which will be detected by the ecu and register a fault code 14 or 15.
However if the temp sensor starts to incorrectly read the temperature (but still give sensible temp readings) the ecu can't detect this and will incorrectly fuel the car leading to bad running.
Therefore if you suspect the sensor you can test it as follows by removing it.
Measure its resistance to find out.
BLUE ECU temp sensors
Measure resistance between the two terminals.
At 100 Deg C 200R boiling
At 25 Deg C 2K - 2.5K
At 4 Deg C 3K - 3.5 K fridge
At 0 Deg C 14K - 17K freezer
Measure the resistance between the metal body and the terminals in turn. Should be infinity.
There are two types black and blue same resistance for both types.
 

[unlucky alf]

An ecu temp sensor can completly fail which will be detected by the ecu and register a fault code 14 or 15.
However if the temp sensor starts to incorrectly read the temperature (but still give sensible temp readings) the ecu can't detect this and will incorrectly fuel the car leading to bad running.
Therefore if you suspect the sensor you can test it as follows by removing it.
Measure its resistance to find out.
BLUE ECU temp sensors
Measure resistance between the two terminals.
At 100 Deg C 200R boiling
At 25 Deg C 2K - 2.5K
At 4 Deg C 3K - 3.5 K fridge
At 0 Deg C 14K - 17K freezer
Measure the resistance between the metal body and the terminals in turn. Should be infinity.
There are two types black and blue same resistance for both types.

Hmmm, sounds nice & technical , I take it the sensor the little thing that is bolted just on the side of the ECU mounting plate, As it goes I happen to have a spare one but never knew what it was , I'll probably swap it out & then test the other one when ive got a bit more time, Thanks for that & i'll report back what the result was,,,,,,,Cheers.

[star_whites]

That's interesting, as I've had a similar problem with my 2001 2.6 on a couple of occasions. I just thought it was down to the maf or bad fuel!.....it's not all the time, just when red hot and it's not all the time!

[Andy H]

That's interesting, as I've had a similar problem with my 2001 2.6 on a couple of occasions. I just thought it was down to the maf or bad fuel!.....it's not all the time, just when red hot and it's not all the time!

OP's car has a BMW diseasal engine. This engine has a well documented issue with a temperamental temperature sensor causing poor starting.

Your 2.6 petrol doesn't have this temperature sensor (or an injection pump.....). The V6 petrol engines favoured mode of failure is the crank position sensor, it doesn't always bring up a fault code but it will fail to start, seemingly at random, until the day it fails properly.

A diesel engine will often run (with reduced power and a confused gearbox) even with a failed crank position sensor.

[Johnny English]

Youve got it TB ive got no codes & no lights, I didnt know that the ECU had a temperature sensor, Also mine being an older one it doesnt have the air intake sensor to my knowledge, Im curious about the fuel feeder suggestion, What exactly would control that & what is the cure?.

The cure is swap or resurrection - the symptoms are indicative of fuel feeder fault, wich is poor start at hot engine and no fault code stored. The temporary cure of that is cooling the body of feeder - even with cold water if no time to wait.  Mind you please, I have petrol car so absolutely no expertising diesels I just had a guess. 

[Omegatoy]

If no problem hot start then it wont be the tuel temp sensor at fault,#
still think its something to do with the pedal  transmitor or receiver in the pump,
reading back it only seems to happen, when the temperature is high, so guessing a dry joint or soimething, think i would try to get a pedal unit and change it as its easier then doing the pump!! however i believe the sensor for the pedal is in the top of the pump,under the top cover so could be fairly easy to do,
unless of course a tech1 or 2 can verify which is not working?
but as you say it would need to be a very hot day to replicate the findings!!

[Johnny English]

By the way you can make a test :  cool off supposedly fault parts with watered rag. Be careful!