The 88' turbo 2 car I'm buying won't hold an idle? Everything I know about piston engines and what I've read about rotary's say's this is an vaccume leak? However I don't understand how a boosted engine uses vaccum, I'm a diesel mechanic everything I work on has a turbo and nothing works on vaccum. Does the engine idle on vaccum, or what's going on here?

Thanks,
Tony

 

It's probably a vacuum leak. Behind the throttle plates, when the turbo is not spinning fast enough to produce boost (any light load situation), vacuum is drawn.

I must point out that this is no different then a diesel application. Though they don't generally have throttle plates, there are many times when the engine is not operating under boost and technically is drawing a vacuum.

 

In addition to a vaccum leak, a metered air leak (air from between the air flow meter and the throttle plates) is also a possibility. The turbo inlet duct (TID) connecting the airbox to the turbo has a habit of cracking over the years. If the leak gets big enough, the ECU will get the mixture wrong and could stall the engine.