FIXED.Thanks Peter you were spot on.the problem was that we dont know the car and it came in as a none runner and when we did our tests and found number 4 injector fault we just replaced it with a genuine one and used the same bolts which were 95mm long but when i removed all the other bolts on the other injectors they were only 84mm approx.so some one had been in there before.so probably already had a misfire.what a crazy system where it cuts engine out completly when only 1 injector becomes faulty especially if your on a motorway.I got some correct bolts and refitted injector and everything ok now.Thanks again for your advice.and autotalk.