- 4 cyl. 6 cyl. V8 & V12
- 318 and 318ti E46 N42 Facelift
- 118 and 120i
- 320i E90 N46
- 5series E60
Symptoms of failure:
- EML light on – yellow light and car warns to drive moderately and have engine checked
- Car loses power – in limp mode
- Heavy on fuel
- Symptoms occur intermittently until car cuts off or refuses to start
- “valvetronic servo motor” faults
- “eccentric shaft sensor” faults – in more extreme conditions and usually cancels out once the VVT motor is fitted
What it looks like:
How it works:
The little electric VVT motor sits at the top of this intricate system and is situated above the cylinder head
This motor turns the eccentric shaft, which pushes the intermediate rocker arms and in turn pushes the valve to open deeper to allow for more power.
Because the lift of each valve per cylinder is controlled or varied continuously according to the revs, the engine will perform at optimum efficiency and hence balance will occur with power, fueling and engine breathing. Note this motor has replaced the conventional throttle butterfly but the latter is still fitted as a back up or safety.
“BMW state a saving on fuel of up to 10%, cold start behaviour, reduces emissions and smoother more responsive power.” It however does not advance top end power.
The VVT Motor and the vanos units usually fail because of sludge. See article on sludge.
1 Day job
VVT motor + Tappet Cover Gasket + Tappet Cover Flange + Software and Labour
We do not recommend fitting used VVT Motors as it is bound to fail and there is no guarantee.
In the 2nd diagram you will see some of the parts that make up the complete Valve Timing system.
- Eccentric shaft sensor (similar symptoms when it fails – will be explained in next article)
- VVT Sensor
- VVT control unit ( not in pic – seldom problematic)
Vanos Unit/Gears – Inlet and Outlet Adjustment Units (not in pic – if the car has single or double vanos variable timing – will be explained in another article)