Help

chaps,

My e39 touring cut out a few days ago coming back from south yorkshire, the car was running perfect and was eating the miles with no problems. However when I stopped at a service station the car cut out. I started it again and it coughed over but I noticed a small missfire when accelerating up from idle. I noticed the performance had dropped away and I could not get rid of the missfire. I managed to get back home and left it a few hours. When it had cooled down, it started as normal and the driving was also back to normal. However the same thing has happened again today. I parked the car up after a 20 min drive and as I came to a halt, it cut out again. Now there is a small missfire between 800 and 1000 revs. Once the car gets past 1k rev mark the missfire dissappears however I can feel the car aint running normal and the gear change is also struggling. I'm thinking it may be the fuel pump on its way out as its affected the performance hence the gear change but is there a way of checking this?. Also could it be one of the coil packs is playing up?. The car is a 528i touring 97 R with 147k on the clock auto box. Any suggesstions would be appreciated.

Sorry for the long post.

Imran.   

cheers Andy,

Just to add to the confusion the ASC (stability control) light has come on and will not go off. Also the car will not start the first time, it takes another attempt before it gets going. Do you think it may be a wheel sensor causing the problem?. Also the MAF and CAM sensor where replaced about 2 months ago with Siemens VDO Original Parts and the Spark Plugs with BMW original's approx 1 year ago. Could these fail so soon?. 

Imran

Just had a mobile diagnostic chap come out and plug his computer into the car. It has thrown up 3 codes as follows:-

1) Crankshaft Position Sensor (code 27 i think)

2) Throttle valve Potentiometer (code 40)

3) Pre Throttle valve control (code 38)

The man said the 2nd and 3rd codes are connected with crank sensor, as soon as this is replaced the ECU should reset and the car should be working fine. If not then the codes will need to be reset. Ill get a new crank sensor and get it fitted. He checked out the ASC but dipically it has not shown up any faults. Can anyone reconfirm if the Crank sensor would cause the other two faults and if replacing the sensor is a hard job. Also if faults codes 2 and 3 are parts which can be replaced.

Cheers Imran.  

Could anyone tell me what the Throttle valve Potentiometer does and where abouts this is located. I have checked the euro car parts website and this is a part which can be replaced, but it does not show an image. Also could you please tell me where the cyclone/oil separator valve is and what it looks like. I would check the real oem website but i dont know what im looking for.

Thanks for the help lads

Imran

Throttle potentiometer (pot) is very similar to a dimmer switch you would use to control lights in your house.

It is attached to the other end of the throttle butterfly valve.  When you press the throtle (and I am assuming your E39 does not have a throttle cable) a electrical motor turns the butterfly valve to alter the air flow into the inlet manifold.  To allow the ECU to "know" where the throttle valve is i.e. fully shut, a bit open, a wee bit more open, or fully open a pot is turned at the same time.  As this is turned the electrical resistance changes which the ECU can pick up on therefore knowing how much the throttle is open.

The ASC fault could well be linked to this as the ASC cuts the throttle and applies the brakes to control any wheel spin.  If there is a fault in the throttle electronics the ASC system will not be able to cut the throttle so throw all the toys out of the pram and refuses to work and tells you by putting the warning light on.

The cyclone valve is the proper name for the PCV system I was feebly describing earlier, cheers John.

HTH

Andrew