P38A Tale of the unexplained..... Que music.

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Mark Piercy

Mark Piercy

Well fumbled member....
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Hmmm. Driving home at a steady 56mph, on a slight incline and the engine died.
It also then started to gear down as it slowed??
I pulled over, it remained idling and as if by flipping magic there were no issues??
The engine light had come initially and then in between each gear down change and then disappeared... The onlt fault I get is a fuel flow error.
So, 1999, 2.5tdi at 230.000mls, on the original pump, engine and box. It is reprogrammed also.
Also once the engine is warmed there is a wobble present.
It will go if the idle is lifted slightly with the acc pedal. Drives without a problem and has shown no other signs since then, even on the same stretch of road.
Battery is good,
Leads are good. Alt stays 14.3v(ive a regulator on order)
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The modulation does sit correct at 96°.
My thoughts are a very worn fuel pump...
If it was injectors the wobble would be a constant upto a certain engine speed or moke but no such signs.
The pump doesn't leak fuel and the system is free of leaks and visual defects. o_O
What are your thoughts please;)
 
In tank pump OK?
That "Fuel flow out of Range" message seems to come up for all sorts of things. When cold, I get a brief flash of the MIL light when lifting off on the project car along with Fuel flow out of Range, despite this, the car runs perfectly and once up to temperature there is no MIL light. However if I look at the modulation chart, there is an anomaly as the engine temperature increases, so could be a worn resistance track in the FIP. Modulation is spot on.
 
RangeRoller dt said:
Is your EGR gunked up?
I’d start with simple stuff when the FIP ages other little issues are enough to upset it. QS starts to act up blip of throttle usually clears it for bit
I’d start with filter/water separator lot of condensation this time of year, lift pump flow check.
Click to expand...
I'd be amazed if Mark has not disconnected the EGR
 
Have you checked or changed the intercooler hoses they delaminate inside and restrict the air flow. mine did that
 
Datatek said:
In tank pump OK?
That "Fuel flow out of Range" message seems to come up for all sorts of things. When cold, I get a brief flash of the MIL light when lifting off on the project car along with Fuel flow out of Range, despite this, the car runs perfectly and once up to temperature there is no MIL light. However if I look at the modulation chart, there is an anomaly as the engine temperature increases, so could be a worn resistance track in the FIP. Modulation is spot on.
Click to expand...
this does suggest simply a tired fuel pump, In all the time I've owned and watched the mileage climb there's never been any issues at all.. At 230.000mls its bound to be starting to struggle..

RangeRoller dt said:
Is your EGR gunked up?
I’d start with simple stuff when the FIP ages other little issues are enough to upset it. QS starts to act up blip of throttle usually clears it for bit
I’d start with filter/water separator lot of condensation this time of year, lift pump flow check.
Click to expand...
egr disconnected years ago my goodman, diesel filter as suggested by the kerm I am Indeed considering.

Datatek said:
I'd be amazed if Mark has not disconnected the EGR
Click to expand...
donkeys years ago.

brianp38dse said:
Have you checked or changed the intercooler hoses they delaminate inside and restrict the air flow. mine did that
Click to expand...
that is always been a suspicion and I may act upon that..
Thank you for your ideas and facts kids:)
 
Mark Piercy said:
this does suggest simply a tired fuel pump, In all the time I've owned and watched the mileage climb there's never been any issues at all.. At 230.000mls its bound to be starting to struggle..

egr disconnected years ago my goodman, diesel filter as suggested by the kerm I am Indeed considering.

donkeys years ago.

that is always been a suspicion and I may act upon that..
Thank you for your ideas and facts kids:)
Click to expand...
Is your MAF sensor still connected if so try unplugging and see what happens Once had similar readings and was faulty MAF.
 
Datatek said:
That's interesting, I might try that:D
Click to expand...
This is how it was explained to me
Right then, on EGR equipped cars IAT is a low preset in the ECU. ECU relies on MAF for running air temp readings. Normally if you have EGR fitted but disconnect the vac pipe to EGR valve car will run normally without issue. However EGR only runs at a steady fairly lightly loaded road speeds. It does not work at idle or on acceleration or when the engine is under load. If the MAF has gone duff and is feeding crap to the ECU the ECU may think EGR is operating and prevent high load fuelling. The ECU will only allow fuel to be injected that can be cleanly burned by what it thinks is the oxygenated air present in the cylinder. If the MAF is telling the ECU the airflow has dropped as it does when EGR is active, then that will cause your problems. If you run the car with MAF disconnected in your case the preset will be used for IAT. This may slightly change fuel usage as the fine metering adjustment extrapolated from IAT/ fuel temp and engine temp will not be as fine. Fitting good MAF is best option.
 
Rubberknees said:
This is how it was explained to me
Right then, on EGR equipped cars IAT is a low preset in the ECU. ECU relies on MAF for running air temp readings. Normally if you have EGR fitted but disconnect the vac pipe to EGR valve car will run normally without issue. However EGR only runs at a steady fairly lightly loaded road speeds. It does not work at idle or on acceleration or when the engine is under load. If the MAF has gone duff and is feeding crap to the ECU the ECU may think EGR is operating and prevent high load fuelling. The ECU will only allow fuel to be injected that can be cleanly burned by what it thinks is the oxygenated air present in the cylinder. If the MAF is telling the ECU the airflow has dropped as it does when EGR is active, then that will cause your problems. If you run the car with MAF disconnected in your case the preset will be used for IAT. This may slightly change fuel usage as the fine metering adjustment extrapolated from IAT/ fuel temp and engine temp will not be as fine. Fitting good MAF is best option.
Click to expand...
Inlet air temperature is measured by a thermistor in the MAF assembly not the metal film MAF element.
With or without the EGR connected, the car will run with the MAF disconnected, in my tests the car used a little more fuel and would give a very small wisp of smoke on heavy acceleration.
Most of the time, a diesel runs with excess air hence the introduction of exhaust gas to limit excess air thus supposedly reducing oxides of nitrogen emission.
As the M51 MAF is a hot film device as opposed to the hot wire device used in petrol engines, failure seems to be very rare.
I will, when I get the insurance sorted, try disconnecting the MAF on the car that gives the "Fuel Flow Out of Range" fault when cold. It will be next year before the new insurance starts.
 
Datatek said:
Inlet air temperature is measured by a thermistor in the MAF assembly not the metal film MAF element.
With or without the EGR connected, the car will run with the MAF disconnected, in my tests the car used a little more fuel and would give a very small wisp of smoke on heavy acceleration.
Most of the time, a diesel runs with excess air hence the introduction of exhaust gas to limit excess air thus supposedly reducing oxides of nitrogen emission.
As the M51 MAF is a hot film device as opposed to the hot wire device used in petrol engines, failure seems to be very rare.
I will, when I get the insurance sorted, try disconnecting the MAF on the car that gives the "Fuel Flow Out of Range" fault when cold. It will be next year before the new insurance starts.
Click to expand...
My original packed in and was replaced with a Chinese copy due to costs. This lasted about 8mnths, would have been better running without it. The one I have had on for 2 1/2 years now is an original from some one I knew who was breaking his P38. The difference in running with and without I found to be marginal. Slight increase in fuel consumption and in cold weather the engine needed to warm up before attempting steep inclines.
 
Rubberknees said:
My original packed in and was replaced with a Chinese copy due to costs. This lasted about 8mnths, would have been better running without it. The one I have had on for 2 1/2 years now is an original from some one I knew who was breaking his P38. The difference in running with and without I found to be marginal. Slight increase in fuel consumption and in cold weather the engine needed to warm up before attempting steep inclines.
Click to expand...
Yes I agree about the fuel consumption and the lack of power when cold proving that fuelling is affected by the MAF as described by BMW.
 
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