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

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

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Average mileage: 134,171 (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
24 people reported this problem
9 people shared problem details
2002 Mercury Mountaineer- 4.6L V8142,000
engine dies and will not idellat a stop check engine light is on
2003 Mercury Mountaineer- 4.6L V8125,000
mechanic changed intake gasket
1998 Mercury Mountaineer- 5.0L V8220,000
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
2001 Mercury Mountaineer- 5.0L V8
When it warms up it stalls
2002 Mercury Mountaineer- 5.0L V8130,000
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
1998 Mercury Mountaineer- 5.0L V817,768
vacuum leak from manifold
2006 Mercury Mountaineer- 4.6L V8116,000
Loud clanking noise when first started then when it warms up it stops
2003 Mercury Mountaineer- 4.6L V8180,000
Exhaust Mel inside cabin. Loss of power. Feels like it won't go into gear.
did a tune up fuel filter an it is still running rough an the RPM are hunting any ideas
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