Car has had a rough idle missing back firing when cold for quite afew months. Tried and checked plugs leads filter etc but could not find the fault. Decided to un plug each injector lead one at a time . Every time i pulled an injector plug the car would run rough like pulling off a spark plug lead. Pulled off the last injector lead(no.1) and their was no change in idle. Left it off and reved it and drove it. Their was no difference in performance. Went and bought second hand one from the wreckers fitted it. The car now idles smooth at 850 rpm put it into drive idle still smooth. Took it for a drive and drives like new again. Checked the old injector and it was stuck open partially. Guessed it had been sticky for at least a year.

might be what my problem is