Hello everyone, I have a 1984 633csi, that idles ruff, no acceleration from a stop, and has black smoke coming from the tail pipe. If I can get it up to 60 mph it runs fine until you step down hard on the accelerator, then it bogs until you get off the accelerator, but once you come to a stop it idles ruff but will not accelerate, it just dies out. I need some help please !!!

At first thought, its definately running rich or the timing has shifted!

Any blockages, dirty filters or faulty sensor can cause your symptoms... Has it been checked for fault-codes?

no it hasn't been checked for faults-codes. Could it be the mass air senor ?

The MAF wouldn't make it struggle at tickover as such, but worth cleaning... Do the Throttle-Body, Idle-control valve, intake pipework and engine breather pipes too ! if this doesn't cure it then we need to get it read for fault codes :)

Hi jumping in on the back of this, my 628 timing went and I lost all power up to about 30mph to the point where actually it would not start, GAV on the forum sorted this for me and we got power back but its been running lumpy and rattling. I since have had the tappets fully adjusted and the air flow was adjusted and power is back and the rattling resolved - it purrs like a kitten. Never had the black smoke tho. Never realised how much those tappets would affect the overall running - may be worth getting someone to loo - its an hours job