Morning ppl i've got a problem with a 525 td i've bought but its not the normal diesel knock. its coming from the top end. i've removed cam cover and span over the engine with a rachet all valves seem to be moving properly. would a blocked injector make the knocking sound? its more on start up when cold and tones down once warm. its intermitent after. when it does knock get plenty of black smoke out the back when boosting up. i've tried injector cleaner in the tank and has calmed down the smoke problem. its like the bat mobile...its the e34 shape on an l reg. i wanna get it sorted cos i wanna take my saab off the road for engine swap kit and alloys. any help would be greatly appreciated. cheers