The early cars came fitted with a ''new'' technology piezo injector to get really high mpg and low emissions but they literally all failed and often very early on. They were on back order at one point the problem was so widespread, initially they just replaced like for like but they failed again usually.

The proper fix was to replace with the older and trusted magnetic solenoid injectors which meant a whole new ECU, harness, pipework etc but they don't give problems.