I have a 1989 760 with 233,000 miles, it would be great to make it to 300,000! Anyway I believe my problem is somewhere in the turbo system. It is intermittent and doesn’t seem to matter if the car is warmed up or cold. When ever the car approaches the turbo range it starts to break down and black smokes bellows as you accelerate. At times the car even runs rough below the turbo range and the performance is greatly reduced. I have gone through and inspected all the Turbo hoses from the air cleaner-to- turbo – to- heat exchanger and to intake. all seem ok and I have replaced some hoses for no particular reason. Strangely enough each time I disturb a hose especially on the turbo side it seems to be much better (for a few hundred miles )then its back to it’s old self. I have also changed the vacuum on the front of the turbo (not the waste gate valve) I’m not sure what it’s called.
Any help its greatly appreciated!!! Paul Anderson

 

You might have a bad mass flow sensor.

Also do the hoses feel really soft?

If so then they might be collapsing under a load.

 

Do you know it there is a test for the mass air flow? I am looking for new hoses on the turbo side as some are soft, still the in frequency of this concer/confuses me.

Thanks for the help

 

The best thing to do is look for a known good used one to try.

You can also look at the hoses.CAREFULLY have someone sit in the car with the e-brake on and their foot on the brake.Then have them give it gas and load the engine.Stand off to the side with the hood open and see if the hoses collapse.