I have a 1987 Buick century 4 cylinder. It is running really rough. If I keep my foot on the gas a little it runs fine but when I take my foot off gas it seems as if it wants to cut off. I know the spark plugs are good. Any help would be appreciated.
A high idle could be the result of a vacuum leak under the throttle body, and will affect the ability of the ECM to properly control the idle, which could lead to stalling. The idle air control, or IAC operates with a stepper motor, which requires some time to reach a correct opening. If the mixture is erratic, the resulting lag could cause a rough idle or stalling. The EGR could also cause this condition if it sticks open. These vehicles were known for both conditions.
〉 Answered on Dec 18th, 2008 by Amanda J. Pierce, MBA "AJ", Certified Mechanic, Project Coordinator; Primavera Scheduler at VIGOR Alaska Industrial Shipyard & BizzM3ch Solutions