I have a Nissan 2003 X-Trail 2.2 DCI Sport. Recently it broke down, making a very nasty mechanical noise from the engine. The car would not start very well and did not tick over. I could drive it at full power but it was very noisy with much black smoke from the back. I took it to a mechanic who said it sounded like the timing chain and tensioner, so he replaced it. I got a phone call later, saying they had started it and it still sounded awful. Now it needs three new valves. Would I have had full power from the car if three valves were bent?