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Matt
Matt, Mechanical Engineer
Category: BMW
Satisfied Customers: 22172
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I hope you can help........ my x3 diesel 06 plate

Customer Question

hello I hope you can help........
my x3 diesel 06 plate will randomly stall once or twice a week ,the car will restart with no problems at all ,and run fine .....I also get the e.m.l. flash on briefly when driving along the car will jump and then carry on as the light goes back out,this aswell only happens very rarely,the car runs fine otherwise......been to the dealer and there are no codes showing up.......ive changed cam sensor ,crank sensor,maf sensor,fuel filter....any ideas its driving me nuts,,,
Submitted: 2 years ago.
Category: BMW
Expert:  Shantal-Mod replied 2 years ago.
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Expert:  Matt replied 2 years ago.

Hello

This could be a lack of fuel pressure from the electrical pump at the tank.

If the connections to this are corroded or damaged then the pump could stop at any time or could not be running at full speed. Check that its relay switches in and out and the relay contacts are clean and bright – replace the relay if in any doubt and do the same for the fuse,
Ideally measure the pressure at the inlet to the main engine fuel pump and if this is low check the pump as described and also consider changing the fuel filter as if this partially blocked this too will reduce pressure.

If both of these are OK then also check the connections to the EGR valve, if either the vacuum pipe of electrical connection are damaged / corroded then the EGR can be on all time which certainly will hurt performance. Its also possible that its a fault with the EGR valve so its worth removing the valve and cleaning it out with brake cleaner, if it looks particularly clogged then replace it.

If this is OK then check the small vacuum lines to the turbo and its connected control solenoid on the bulkhead, any cracks or leaks can give turbo issues and its best to have the boost pressure measured actually measured with a boost gauge to check that the turbo is healthy and that the sensor is reading correctly

If its a variable vane turbo (they’ll be an actuator on the turbo body - but not a wastegate) then check its vacuum pipework as above and check the connections to the diaphragm / solenoid valve

Also worth checking that the glow-plug relay is switching off as they can stick on and leave the glow plugs also on - on some cars this can force it into limp home

Customer: replied 2 years ago.

hello I had a new turbo fitted last October so should be fine,ive checked fuses and fuel pump relay all ok,new fuel filter has been fitted all ok.the E.G.R has been cleaned while the car was de-flapped still all clean.new glow plugs have been fitted with control unit that's all ok...the car will only do it from cold when operational temp is reached the cars never done it.after the E.M.L. flashes its about a minute then the car stalls.... fuel pump maybe ???..........the D.D.E/E.C.U looks fine with no signs of any water ingress........cheers andy.

Expert:  Matt replied 2 years ago.
Hellothanks for the extra information, I'd suggest checking over the electrical connections This could be a wiring issue as things tend to expand when hot and its possible a poor or partial electrical connection is being pushed apart on one of the major sensors so check the connection plug and wiring to the following;Airflow meterCrank position sensorCam position sensorO2 sensorThrottle pedal position sensor
Expert:  Matt replied 2 years ago.
Hi

do you still need help with this?
Customer: replied 2 years ago.

hello checked all connectors and plugs cleaned all aswell....not sure if the diesel has a throttle pos sensor thou.......still the same outcome,i will add the car started doing it after the new turbo was fitted...coincidence maybe.......

Expert:  Matt replied 2 years ago.
Hello

OK thanks for the extra information

This could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out and can also allow the engine to rev up when not desired causing rough running.

As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak.

Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.

Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

Expert:  Matt replied 2 years ago.
hi

do you still need help?