Last night I took my car out for a short run - about a mile. All was fine. About an hour later I went to start it. It fired up as usual, but the engine started hunting badly, from between about 500 - 1500 revs. It also was blowing a bit of soot from the exhausts, and there was a strong smell of unburnt petrol in the exhaust. I tried switching off & on a few times, but same thing each time.
I went inside & had a think. About a year ago, I filled up with fuel after a long run (Shell Optimax as always), and on the trip home from the fuel station the engine died several times. I was wondering if I'd overfilled the tank or maybe filled a breather or similar. The problem however did not persist.
I had recently filled up (to the brim) and this was the first run since filling. I went out and undid the petrol cap, just to see if it sucked in any air, but appeared not to. I tried starting up again, and it ran perfectly. Any ideas what the problem may be? Mine is a pre-catalyst btw.
Thanks
Richard