misfire?

Or a leak down test. This involves bringing the piston on the cylinder to be checked up to Top Dead Centre (tdc) then, using an adaptor screwed in to the spark plug hole, fill the cylinder with compressed air.

If you have a badly seated intake valve you will hear or feel air coming out of the throttle body.

If an exhaust valve is faulty air will come out of the exhaust (tip - fix a rubber glove over the end of the exhaust pipe using tape or an elastic band, if it inflates, you have a leaky exhaust valve).

If you feel air coming from the dipstick tube (stick removed) or oil filler cap, you have a badly worn bore, failed piston ring or a hole in the piston.

If you get bubbles in the coolant you have a blown head gasket or cracked cylinder liner.

If you get air in one of the adjacent cylinders, you have a blown head gasket between cylinders.

Hope this helps you pass your exam!!

vaux
December 2009

Compression test, first with a dry engine note the compression then add some oil into the sparkplug hole then test again, if the compression rises it's a worn bore/piston rings if no change it is a head/valve problem, other method an endoscope/boroscope inspection

nigel
December 2009