How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Matt Your Own Question
Matt
Matt, Mechanical Engineer
Category: BMW
Satisfied Customers: 21851
Experience:  BEng hons Mech engineering, in auto industry 22 years
12772297
Type Your BMW Question Here...
Matt is online now

I have a MINI ONE D 03 plate . The problem is intermittent.

Customer Question

I have a MINI ONE D 03 plate . The problem is intermittent. If you are at very low revs, say taking a roundabout in 2nd, the engine just stops. All the lights come on. You dip the clutch and turn the key and it starts up and drives as normal. All the lights reset and it may go a week before it happens again. It may happen on the next roundabout. If you leave it at idle for a while and then try to rev it, it just stops when you press the throttle pedal. Otherwise the car drives well and has good mpg. No smoke. Always starts first time. I have spent £120 so far on diagnosis from "experts" who just walk away scratching their heads. So far checked cam sensor, filters in stop valve, new fuel pressure sensor, new fuel filter. The only code showing is P3002 fuel pressure issue (before we changed filter). It has 124,000 on the clock. Getting close to getting rid of it. Please don't reply unless you have a good idea as I am fed up with paying for advice that has not changed a thing. PS it's been on BMW diagnostic, no joy. Thanks.
Submitted: 1 year ago.
Category: BMW
Expert:  Matt replied 1 year ago.
Hello this sounds like a lack of fuel and could be a lack of fuel pressure from the electrical pump at the tank. If the connections to the pump 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 pump and if this is low check the pump as described
Customer: replied 1 year ago.
I don't see why it would only stop when fuel demand is low ie at below 1000rpm. It never stops at normal driving speeds, so lack of fuel doesn't seem likely. An electrical fault cutting out as though the the key has been turned off is how it presents itself. One other thing I didn't mention is that the headlights dim slightly when engine reved. I don't know if there might be a connection?
Expert:  Matt replied 1 year ago.
Hello Ok thanks for the extra information as the next step I'd pop the auxiliary drive belt off and turn all the ancillaries by hand, feeling for tight spots on all the pumps and especially the alternator Also check that the alternator is actually charging the battery in the car by taking a battery voltage reading with the engine off then another with the engine running. The 2nd reading should be higher than the 1st and climbing steadily. And also check that the alternator is secure to the engine as this provides the ground for the charging circuit and make sure that the engine / gearbox earth strap is secure and the contacts are clean and bright. if the alternator appears not to be working - take it to a electrical specialist and ask them to test it as sometimes you can replace just the diode pack and this will repair the alternator without requiring replacement
Customer: replied 1 year ago.
Battery charging fine loads of life in battery. Engine turned over strongly when fuel filter was changed. Starts first time. It feel like it must be electrical. Something like the throttle pedal or engine stop, immobiliser, ignition switch?. If you try to rev the engine it just stops, but only now and then. I'm beginning to think this is going to beat me. The previous owner had parts fitted and then got rid of it for the same reason. Even BMW are stumped. Pity, it's such a good car in every other way.
Expert:  Matt replied 1 year ago.
Hello Ok in that caseThis 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 position sensor unplug each in turn and use some switch / contact cleaner spray on the pins to ensure its all grease / dirt free Also worth checking the connections to the fuel pump for the same reason - unplug each in turn and give them a good squirt of switch / contact cleaner - Not WD40 and also unplug and inspect the main power relays and fuses for signs of overheating or corroded terminals - so the ones for the ECU and the fuel pump And also unplug the wiring loom connections in the engine bay one at time and inspect for corroded or recessed pins.
Customer: replied 1 year ago.
I'll try a few things tomorrow. Do you know where these sensors are? I've done the cam sensor and relays and ECU but I don't know where the others are. If not I'll try and find out on line. Thanks
Expert:  Matt replied 1 year ago.
hello the MAF is on the air intake just after the air filter box the throttle position sensor is built into the throttle body on the engine intakeand the o2 sensor is on the exhaust, there should be 2 of them 1 after the other
Customer: replied 1 year ago.
Sorry Matt. No joy. I have decided to fit a data logger and run the car for a week and take a look. The most common thoughts are that the low pressure pump is failing at idle. I have noticed that this fault occurs on petrol models too, as well as the Yaris with the same engine.
Expert:  Matt replied 1 year ago.
Hello thats quite possibleIf the connections to the pump 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 injectors 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.
Matt and other BMW Specialists are ready to help you
Customer: replied 1 year ago.
Hi Matt. Most of the things you point out have been done. We fitted new filter and checked relays, new fuel rail sensor, cam sensor and checked and cleaned all connections. Thanks for your help. Unfortunately we still have the problem.
Customer: replied 1 year ago.
Fitted Sykes Pickavant data logger. Will run car for a week and look at data.
Expert:  Matt replied 1 year ago.
understood