I have a 91 740 Turbo with 180,000 that just doesn't want to run smoothly on a consistent basis. Some days it runs great, other days which are becoming more frequent, it runs awful. It will be going along smooth then out of the blue it loses power, sputters, if I take my foot off the accelerator the RPM goes to 0, at a stop it will stall but start right up again. If I give it gas when this is occurring, it will run real rough for about 5 seconds then blow black smoke and run great again. It seems to happen after I have been on the highway then slow down. It also seems to act up when I am on a bumpy road. The wires, plugs, cap and rotor were changed not long ago and are all tight. It seems to be fuel related ie the black smoke but I just don't know. Today it stalled turning into a parking lot. When I started it back up the lights on the dash (not all; just service, light out, battery, brake, parking brake and ABS) came on and now they are staying on. I hope someone can assist as I am about ready to give this to my 15YO and tell him to have at it!