m51d25 loses power

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the injector light on these is also for telling the driver that the car is in limp-home-mode IIRC. :D

as for the FIP, it's a new part and i did the install myself. i timed it to spec with the right tools and a gauge. but again, the problemmmm was there before i replaced the pump. the pump was replaced because it was leaking, and i though the problem might have been there. wasn't.
turbo is also new, and was replaced because the previous owner (and possibly by owners even before him) had ruined the turbine by not replacing the air filter often enough. quite important with turbo engines.
the turbo is behaving normally. same performace (pressure-wise) at the same speeds, with or without the loss of power. i.e i creates as much of boost and the same sound when driving at, say 80kph, when giving the same ammount of fuel (10L/100km).
bimmers have that gauge, as you know. :) (mostly useless really)

i feel like i should point out that the fault was there, before i changed any of the parts i listed in the original post. :(

something is definely limiting fuel flow here. i think the most obvious sign of that is the "mpg gauge" (for you lads) not rising above that 10L/100km mark. o_O
 
You've replaced just about everything! Even the loom. That was a good call with it being sudden and coming back if you backed off. Does sound like it could be an electrical connection.

Is the number 4 injector on your list of replacement parts?
 
Grrrrrr said:
You've replaced just about everything! Even the loom. That was a good call with it being sudden and coming back if you backed off. Does sound like it could be an electrical connection.

Is the number 4 injector on your list of replacement parts?
Click to expand...

i'm sure it'll get replaced eventualy, if the problem is not solved before. might even be quite soon-ish.
 
Grrrrrr said:
You're considering the BoM fix?
Click to expand...

oh no not quite yet. :D this is as much pain to me as it is intriguing. i've worked in the industry nearly 15 years now. never have i come across such a bizarre problem in a car.
all of those parts i've replaced, were supposed to cause similar or the same problems. it's hard to say now, if bosch did a rubbish job with the electronics of the thing. if the failure of pretty much any component can cause this problem.
because after all, this is pretty much 1st gen diesel electronics. but then, they already had years of experience with petrol electronics, and diesel electronics are actually not that much different, from what i understand.
 
As said before diesel engines are pretty simple pieces of kit. For any given throttle setting, power demand, manifold pressure they will ALWAYS have the same amount of air in the cylinders. The only thing that changes is the amount of fuel. If you remove the turbo from the equation for a moment, it makes things easier to understand. Forget the turbo and in a none turbo diesel there is the same amount of air in the cylinders at idle as there is at full throttle. The only thing that changes is the amount of fuel injected into that air. More fuel the bigger the bang, the more the power and RPM. It really is as simple as that. If you have the correct amount of air then the only thing that can cause the engine to lose power is a restriction in fuel. Duff engine sensors can cause this. ECU temp sensor, Engine temp sensor, Fuel temp sensor. Or maybe a sensor not transmitting a signal the ECU expects to see and confusing it. Whilst the MAF sensor and EGR modulator have no effect on fuelling as such, them giving incorrect or no information to the ECU can confuse it and cause it to misinterpret air conditions. That could alter injected fuel and cause power drop. It is in the BMW service sheet i posted. All it takes is the ability to understand what it says and act on it.
 
update. drove about 450km to go backpacking, came back and the oil warning light (pressure or level) wont turn off anymore. but the engine has enough oil and definitely has oil pressure. oil pressure sensor is a new bosch replaced about two months ago.
my guess is the oil level sensor has gone bad (iirc common to all 6cyl e36's).

could there be any relation to the issue here?

the engine has now done 440 000km.
 
mazappi said:
update. drove about 450km to go backpacking, came back and the oil warning light (pressure or level) wont turn off anymore. but the engine has enough oil and definitely has oil pressure. oil pressure sensor is a new bosch replaced about two months ago.
my guess is the oil level sensor has gone bad (iirc common to all 6cyl e36's).

could there be any relation to the issue here?

the engine has now done 440 000km.
Click to expand...

EDIT: the warning light can be for both the pressure and the level of oil, in these cars.
 
mazappi said:
EDIT: the warning light can be for both the pressure and the level of oil, in these cars.
Click to expand...

If there is circuitry on your vehicle that cuts power if it detects low oil pressure then yes that would maybe cause a problem. Whether such circuitry exists on your vehicle i have no idea.
 
crossing over "oil level sensor"... just when i got my hopes up.


i.e. i replaced the oil level sensor, warning light is gone. the (main) problem isnt.


...adding "50 pounds of TNT" to the end of the list...
 
mazappi said:
crossing over "oil level sensor"... just when i got my hopes up.


i.e. i replaced the oil level sensor, warning light is gone. the (main) problem isnt.


...adding "50 pounds of TNT" to the end of the list...
Click to expand...

No need to be extravagant 5 pounds will do it.
 
today, i have been mostly eating... no wait.

today, i removed the OEM lift pump, and put a facet clickety-klack pump in it's place, with constant power running from a switch.

zero. b-b-b-... difference.
 
...what i still think is the weirdest thing, and also maybe the strongest lead, is when i drop the revs below 1000rpm even for just a fraction of a second, the power is back.
and it's THE only thing that returns the power back to normal. not even coasting for all ethernity does it. unless i coast till less than 1000rpm, i guess. haven't tried that yet.

what i once read from this forum was the the throttle potentiometre could be telling the ECU that the car is at standstill (no trottle applied) whilst also still telling the ECU throttle position data.
i.e. the potentiometre is telling the ECU both: no throttle being applied, and how much throttle i am actually applying, confusing the ECU, which then could be cutting power.

filled with hope, i replaced it with another used one. no difference what so ever yet again. i know it's a used part and it could have the same problem... but the seller was very reputable with 99.7% positive feedback at some 30 000 sold items.

a new one would've been 200€, which for some reason was now too much. even though 700€ for a rebuilt pump wasnt too much, even if the old one was just leaking...:rolleyes:
 
mazappi said:
...what i still think is the weirdest thing, and also maybe the strongest lead, is when i drop the revs below 1000rpm even for just a fraction of a second, the power is back.
and it's THE only thing that returns the power back to normal. not even coasting for all ethernity does it. unless i coast till less than 1000rpm, i guess. haven't tried that yet.

what i once read from this forum was the the throttle potentiometre could be telling the ECU that the car is at standstill (no trottle applied) whilst also still telling the ECU throttle position data.
i.e. the potentiometre is telling the ECU both: no throttle being applied, and how much throttle i am actually applying, confusing the ECU, which then could be cutting power.

filled with hope, i replaced it with another used one. no difference what so ever yet again. i know it's a used part and it could have the same problem... but the seller was very reputable with 99.7% positive feedback at some 30 000 sold items.

a new one would've been 200€, which for some reason was now too much. even though 700€ for a rebuilt pump wasnt too much, even if the old one was just leaking...:rolleyes:
Click to expand...

Throttle pot switches ECU to idle mode below 9% travel where the fuelling is controlled subject to signals from the Crank speed sensor. Above 9% ECU fuels according to power/throttle request. You should be able to check pot linearity with diag.
 
dubbleRR said:
Would a faulty brake light switch cut power to the engine ....
Click to expand...

I would not have thought so. Why would it? It would certainly bring up an ABS fault on the message centre if the stop lamp switch failed to make on brake application and would effect cruise control if the other switch failed to make or break. The brake switch is a make and break switch. When the brake is off cruise control circuit is made and brake lamp circuit is broken. When brake is applied cruise control circuit is broken and stop lamp switch is made. The switch swaps senses when the brake is applied or released.
 
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