Today I drove the Daimler Century to the MOT test. Car hadnt been used for 6 weeks.
Started & drove there perfectly. During the emmisions test it suddenly started missfiring and stopped. Difficult to re-start and would only start by flooring the throttle. It would run at about 2000rpm but badly. In the end we had to abandon the test. The emmisions were not too bad and were coming almost within the requirements as it got really hot, fans running on full speed. I changed 5/6 plugs as I only had 5 in the boot! Also changed one coil as one wasn't OEM and I always carry spares. It would restart but still running rough and rich. Limped home in second to keep revs up. I then went to get some fuel and it was running ok but not nearly as lively as usual. Fault code P1621 which other posts say doesn't exist on an X300!
Any thoughts???
Thanks
Charlie

 

Crankshaft position sensor. Not a suggestion based on mechanical logic, but a known X300 weak point, and we have had a run of cases on here where cars which ran well were laid up for a while, and then had an assortment of rough running/ poor starting issues when returned to service. Not a difficult or particularly expensive job, and worth doing anyway, so maybe a good place to start?

 

I had replaced the crankshaft sensor last year and fitted one of Andy's brackets. After the fuel trip I took it out again as my fault code reader wasnt working and drove about 10 miles to a friend who has one. Car ran ran as it should although P1621 had come up again. Drove the long way round to re-test today to get it thoroughly warm and it passed with flying colours.
CO 0.00
HC 24
Lamda 1.000
Cant get much better than that!