Folks,

My '88 765T has developed a problem where it blows black smoke under certain conditions. It is easiest to get it to do this when I'm cruising on the freeway at moderate speeds -- say 60 mph. If I apply a slight amount of pressure to the accelerator, the car actually slows a bit, and the exhaust will emit black smoke. If I apply more pedal, it then snaps out of this, and behaves normally. No black smoke, either.

I have removed all the turbo hoses and manipulated them, looking for even the smallest of holes. They all appear to be fine. So do the various vacuum lines, as far as that goes. While I had the hoses off, I tried spinning the turbo's impeller. It spun smoothly and exhibited no play that I could detect.

I noticed, though, that the fuel pressure regulator appears to have a slight fuel leak -- it's hard to tell where the leak is coming from. This got me to thinking. I know that an fpr can fail such that the fuel pressure will be higher than normal. If this should occur, it seems to me that an over-pressure condition can result in too rich of a mixture. I don't have the equipment to test my car's fuel rail pressure, so I don't know at this point if the fpr is a problem or not. It seems, though, that it could at least be a candidate.

I'm curious as to what others here might think. Besides the above, is there anything else I should look for?

Thanks in advance,
Michael McBroom