My friend has a 1997 Z3 which will run for a few miles then cuts out. Will start and run again then intermittently cuts out. He has had crank shaft cam shaft sensors changed. I know probably could be anything, but I thought that I would ask. 

First thoughts were cam / crank sensors but unless the new ones are faulty then I would start looking at the fuel system.

If the car has been stood for a while then I would firstly look at changing the fuel filter - rarely changed as its an expensive part and also tucked away under the sill.

Also look at the battery connections and it may also have an SRS power cutout on the positive cable which may also be faulty but be careful testing this as it has an explosive charge

Thank you I will get him to look at that.

On 11/04/2025 at 08:52, Brian 23 said:

Thank you I will get him to look at that.

How have you got on with diagnosing the fault?
Had to do a running repair on my Z3 in the week as the original intake trunking had perished and was drawing unregulated air through the hole and the car ran incredibly rough - replaced the part with the new one that I had in the boot for years and runs great now

Another thing worth trying when its running on song is using super-unleaded - has made the world of difference the flat spot at around 2000rpm which has disappeared since using the higher octane (and lower ethanol) fuel