The coils are on top of the spark plugs, under the cover down the center of the head. There are three connectors one for each coil that go from the coil to the spark plug. These are cheap and fail regularly.

We often replace all three when replacing plugs as determining which is failing can be a problem and problems can be intermittant. You should eventually get a misfire code that will point out the bad cylinder, but without a good scanner it will be hard to pick it out untill the code sets.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician