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Rough idle 1999 mercury mystic

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Anonymous

16y ago
Updated: 8/17/2019

Could be lots of things:

Idle control valve

Failed or failing spark plug/lead

MFA (Air/fuel mixture meter)

Automatic choke stuck open when hot

ECU (brain)

Defective coil pack

Etc etc

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Wiki User

16y ago

What else can I help you with?