Hello,

I was driving my '85 740 Ti to school today, just cruising along (turbo wasn't adding pressure or anything), and all of a sudden, it starts running really rough--like it's running out of gas, only without the knocking or anything. The throttle won't respond--it's too busy trying to keep itself on--and then I hear a pop and a short hissing sound that comes from the rear-left of the engine compartment, around the brake booster. I assumed it must've been a blown head gasket, with the hissing, but it didn't KEEP hissing. Only hisses when the turbo spools up (which it does, perfectly normally; i hear it every time). AND after that happens, I realize, the power brakes stop working.

I stopped for gas and had a look, and nothing appears to be wrong. But when it's idling, which it does very roughly, I hear that same hissing sound, which is as rough and inconsistent as the idle. It goes away when any pressure is applied to the throttle, at least, till the boost meter goes into the yellow range. It was running strangely this morning when I started it; I started it, it stalled. I started it, it stalled. It must've done that three or four times when it started and idled very roughly--much in the same way it does now--but I gassed it and it picked itself up. I figured it was just a simple cold start thing; it was freezing outside.

I have had no problems with this car previously, though I've only owned it for about a month and a half. What's wrong with it? This is pretty urgent. I appreciate your help.

Thanks,

Volfro
85 740Ti