The intake manifold gasket can fail causing vacuum a leak and/or a rough idle condition. Replacement of the leaking gasket will be necessary to correct this concern.
Car Problem Reports
Mazda 626 Intake Manifold Vacuum Leak Causing Rough Idle
Mazda 626 Problem
Model Year Affected: 1998
Engine Affected: 2.0L 4 Cylinder
Visitor, 1998 Mazda 626, 2.0L 4 Cylinder, 175,000 mi
Surged to the point of stalling. I ended up spraying carb cleaner at the point where the intake met up to the head and found when spraying the carb lceaner at the no 1 cylinder, the engine speed noticibaly changed. The Intake gasket was replaced and the issue was resolved.