* Rough Idle/Stalling: A significant vacuum leak will disrupt the precise air/fuel mixture entering the cylinders. This leads to an erratic idle, potentially causing the engine to stall, especially at low RPMs.
* Decreased Engine Power/Performance: The engine won't produce its full power because the air/fuel mixture is incorrect. You'll likely notice sluggish acceleration and a general loss of power.
* Increased Fuel Consumption: The engine will run "rich" (too much fuel) trying to compensate for the lean mixture caused by the air leak. This results in lower gas mileage.
* Check Engine Light (CEL): The onboard diagnostic system (OBD-II) will almost certainly detect the problem and illuminate the check engine light. A code related to a lean condition (P0171, P0174, etc.) will likely be stored.
* Backfiring/Misfires: In severe cases, the lean mixture can lead to backfiring through the intake or exhaust, and/or misfires in individual cylinders.
* Hard Starting: It might be more difficult to start the engine, especially when cold.
* Vacuum-Related Problems: The intake manifold is a source for many vacuum lines that operate various engine accessories like the brake booster, power steering assist, etc. A leak could affect their operation.
Where the Leak Might Be:
The leak could be in several places on the intake manifold itself:
* Gaskets: The most common location. Gaskets seal the manifold to the cylinder head and throttle body. These can deteriorate over time due to heat and age.
* Cracks: The manifold itself can crack, especially due to thermal stress. This is less common but possible.
* Vacuum line connections: Leaks can occur at the points where vacuum lines attach to the manifold.
Important Note: It's crucial to get the leak diagnosed and repaired by a qualified mechanic. Driving with a significant intake leak can cause further damage to the engine. A simple vacuum test can often pinpoint the leak's location.
