I have a lovely but rarely used 1977 XJ5.3C which starts first time and runs for about 20 minutes before cutting out. I have replaced fuel and air filters but this hasn't improved things. I need to sort this out so that I can get the car motd and (regrettably) sold (if anyone is interested the car is in vgc). The last time I attemted tomot the car (2 years ago) it failed on emissions. Since then I have started the car regulalryand run it for about 30 miutes until warm. However nowit will only run for about20 minutes before it cuts out nd then have to wait until cold for it to start again. Am wondering if it could be the dreaded early Lucas ecu? Anyone any ideas?