Vacuum leak from intake manifold O-ring gaskets on Mercury Mountaineer

Problem Description and Possible Solution

The intake manifold O-ring gaskets commonly leak, causing stalling and poor idle quality; the Check Engine Light will illuminate.

Problem Data
RepairPal Verified
Average mileage: 137,660 (14,000–235,000)
Engines affected: 4.0L V6, 4.0L V6 SOHC, 4.6L V8, 5.0L V8
8 model years affected: 1998, 1999, 2000, 2001, more2002, 2003, 2005, 2006
26 people reported this problem
Viewing 1 - 10 of 10 comments
Rough Idle and throwing engine codes p0300 random engine misfire. Before replacing gaskets I bought 2 new coil packs and new wires and plugs (performance) spent about $275 and still had problems like no other. Buying gaskets now and putting them on and its fixed
engine dies and will not idellat a stop check engine light is on
Vehicle shuts down at an idle or a slow speed or at a stop sign have to put in n and it starts right back up
mechanic changed intake gasket
vacuum leak from manifold
Exhaust Mel inside cabin. Loss of power. Feels like it won't go into gear.
Not fixed yet... Will be hopefully after this.
When it warms up it stalls
Loud clanking noise when first started then when it warms up it stops
did a tune up fuel filter an it is still running rough an the RPM are hunting any ideas