I have a 1.4 V reg. 16v with 110K miles on the clock, it starts without any problems but it developed a misfire and the fuel comsumption dropped from 37 too 20 mpg. I changed spark plugs and all the ignition coils and it ran like a dream, for a couple of days. Then when driving along it was if someone had flicked a switch and the misfire came back and the consumption dropped. Does anyone have a thought on the problem?