Vaccum/Boost Question
02-08-10, 09:41 PM
#1
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Vaccum/Boost Question
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
Thanks,
Tony
02-09-10, 09:49 AM
#2
Engine, Not Motor
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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.
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.
02-09-10, 03:19 PM
#3
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.
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