2002 Ford Fiesta 1.3 8v issues

Hi all,

I have a 52 plate MK6 Ford Fiesta Finesse 1.3 with running issues. So a few weeks ago my Fiesta cut out a few times and stalled when slowing down with the engine being difficult to restart. Started using E5 petrol and hoped the issue had gone away. Several hundred miles later it did the same thing. Slowing down in traffic, revs going really low, difficult to restart, can be pretty dangerous. Car often revs too high when idling while engine warm too, might be related.

This weekend tried putting on a new idle control valve which didn't seem to work at all, just kept reving. Put the old one back on, slightly better. Changed the injectors for new ones, now I can't start the engine without applying gas when starting over and the check engine light came on, scanner reported misfire on cylinder 4 (that's the third one in from the timing chain end right? If we're going by firing order) put the old injector back on the cylinder and still seems the same, difficult to start. Car seems to idle ok other than too high again sometimes and seems to drive ok.

Does anyone have any ideas or advice? Is the car safe to drive on the motorway or should I definitely start looking for a mechanic to have a look? I really don't want to cause the car any damage or be stranded away from home.

Another question to ponder is do you think 15,000 miles a year is just too much for a car it's age now? Currently has about 88000 on the clock.

Thanks.