I attended a 4 day Rally from Switzerland to Paris with "D". The driving and the different stages within those days was extremely nice. Overall, we drove on yellow and white indicate French roads only with about 200 cars participating. (Probably 30 of them blew off because of the tremendeous heat situation wheterwise). Anyway the whole rally lastet for about 1800km, including the return back home. It included many inbetween phases to recalculate your way and arrival time as usual on such happenings. Over time, one had to stay in line to approach the next test and thats were most cars blew off.
Anyway, "D" behaved as usual flawless until the start of the last rally, which started at the old Reims racing circuit. When I drove away, some small "explosion" noise from the engine occured and suddenly the car was not running on all 12 anymore. After some 10 minutes into my carefull (or better frightfull) running, the engine came better again but not perfect. I mobiled the supporting mechanics to make sure that after the following 200 km run they would prepare everything to support any findouts at the end of the rally.
5 hours later when arriving in the finishing zone the righ away checked the car and found out, that 1 spark plug was wet/fouling and not functioning. They checked all ignition cables, made compression tests and found out that the compression was 10 on the cylinders and 8.5 one the "fouling spark plug" cylinder. But they also said that this difference may well come from the fact that this lower pression cylinder is now full of unburned mixture and therefore less compressing (which should be o.k. again by now). So they change the spark plug and "D" runned again on all 12. But they found blue smoke on the exhaust from the "fouling cylinder" and asked me to stop right away the engine and suggested to load "D" on the transporter and not drive it home again as any possible and serious problem could be the reason fro the blue smoke.
I asked them then if the smoke could not come from the unburned fuel micture which needs to be blowed off first ? They said that this is quite possible but it also could come from a partial distruction of a valve
. By now my heart fell to my toes.....
To make a long story short, I did not believed them and suggested that I start the engine again, make some round around the mechanics car and if o.k. drive to the hotel (20km's) in Paris. Already after the rounds done the smoke was gone and I drove to Paris, checking the smoke again and everything seemed o.k. Finally I decided to drive the 600km's back to Switzerland the next day. The car runed on all 12 all day long whereas I never exceeded 4000 rpm's.
After driving for about 2 hours the engine "spit" sometimes little "blows". On such occasions, the Anameter (electricity gauge) shortly and wildly moved away from the normal "0" line. These spits came every minute for an hour or so but then ceased for another hour before it happened again. Temperature of Oil and Water never exceeded 70 Celsius degrees and Oil pressure was always normal.
After I came back my mechanic told me that this may come from a carburator setup which may be a little to tiny (the opposite of a fat micture) but it may aslo be because of the great heat as well as the micture in the carburator almost vaporises. Well I have no idea but any experience of you mechanic guys out there are very welcome !!