Hey Scotty, my mother has a 2009 BMW Mini N12 engine 1.6 litre petrol with 70000 miles which is pushing out too much NO (nitric oxide). A garage hooked up an exhaust gas analyser which showed that…

earthy mike

Hey Scotty, my mother has a 2009 BMW Mini N12 engine 1.6 litre petrol with 70000 miles which is pushing out too much NO (nitric oxide). A garage hooked up an exhaust gas analyser which showed that while the car was being revved constantly at 2000rpm the NO would slowly increase as a % of the exhaust gases, which increased to waaaay more than the allowed amount for the MOT test.

The garage said it was definitely the timing being out of whack due to a stretched timing chain. I bought the camshaft and crankshaft locking tools and managed to bolt them on to the engine, then rotated the crank shaft four times and was able to fit them on again. So the issue is not the timing. Every thing under the engine cover looked great.

Can you give me another idea of what might cause a steady climbing NO reading in the exhaust gas while the engine is being revved?

Cheers from Mike in Cornwall, UK!

Comments (6)
No. 1-2
earthy mike
earthy mike

Thanks for your reply Dil. If the crankshaft can be locked into the timing position (which on this engine is pistons in the middle of their travel), while at the same time the camshafts are locked into their timing positions; then the engine is in time.

If you rotate the engine several times and the engine is still in time, then this is a confirmation that the engine remains in time; and doesn't go in and out of time as it's being rotated. If the chain is slacked then the result of this would be an engine out of time.

dil 89
dil 89

Was the timing chain slacked? Taking them off rotating the engine and being able to put them back on doesn't mean anything. Also your exhaust could be clogging up