Change your PCV if you have one...
First the Crank Position sensor and now I've had a double whammy. The PCV valve and hoses associated with it were toast. I also had a nice oil leak develop which was my valve cover gasket @ 186000km.
From 155000km -186000km
Engine Speed Sensor ($1000)
Crank Position Sensor ($180)
PCV Valve and Hoses ($225)
Valve Cover Gasket ($135)