Just completed a engine change on this 6cylinder petrol 3 series.

All went well and replacement engine was the same apart from one thing..


The knackered engine had crank sensor located near the flywheel picking up the signal from a reluctor ring on the crankshaft.

The new engine used a reluctor ring on the crank pulley at the front of the engine. But it did have a cover over the rear of the engine to locate the same type sensor as on the old engine , however on inspection there was no reluctor ring on the crankshaft. I had to use the front sensor to give the signal to the ecu.

My big question is would you expect it to affect the running of the engine???

The car will start every time and drives but takes
approx 4-5 turns to start and often is a bit lumpy
on start.

I would have thought if the crank sensor is there to find TDC it would be the same point of turn wherever the sensor has been fitted.??
Could it be inlet gaskett or vacuum pipe at fault as i let my apprentice remove and fit the inlet and cant see much without stripping it to be sure its back right.

You have whole load of trouble coming your way.

"All went well and replacement engine was the same apart from one thing.." and what have you based that decision on ???????

going on the limited info you have provided (no engine codes ) it sound's to me like you have fitted completely the wrong engine.

You say your car is a 2003 which would make it a E46 model. The six cylinder engine for this model range is the M54 and M54TU. This engine has double vanos units and MS43 management system.




If you say the donor engine has the crank sensor on the front crank pulley this would make it a M52 engine ( single vanos also MS40 management system). also it is from a E36 model.




I'm amazed it runs., you must have plenty of unused connectors on the engine loom.

think you need to go and visit spec savers