In the process of trying to fix my Sierra 2.0i DOHC which recently failed its MOT on high emissions I stuck some injector cleaner in a tank full of petrol and drove from Bradford to Sunderland. I gave it a good thrashing and went and watched a sh*te football match. Got in the car to go home and the damn thing was misfiring at low-medium revs, idling speed had become low and sometime cutting out. Things improved when it warmed up and especially at higher revs.
The next day the car was embarrasing to get moving as it was in full kangaroo mode until warm when the symptoms (mostly but not completely) disappeared.
What would cause an engine to get worse after treating it with injector cleaner and giving it a thrashing?
tia
Antony