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Engine starts but runs erotic and will not idle, it has what seems to be a vacu on 1991 GMC Vandura 2500

It has what seems to be a vacum leak but all hoses are on.it dies at low idel. Unable to drive engine dice when put in gear. Possible MAP where it where it is.

SCAN TEST, (IAC). Light on? Any vacuum leak at or around the throttle body, especially the gasket, will result in very high idle speed!!! Have the idle air control checked with a scanner!
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2 more answers
agree with goodguy
check the throttle body gasket