1999 Ford Explorer • 184,000 miles

The engine runs smooth until it warms up, then it intermittently idles and runs rough. I doesn't have a trouble code yet but I took it to a shop last week and they said that the timing was the issue. That the timing is advanced and retarded mechanically through the crankshaft hydraulically. Is that true? How can that be? It seems like the engine is missing because of a faulty sparkplug, sparkplug wire or a coil. Possilbly a fuel injector issue but I already tried to clean the injectors with no luck. Have you ever heard of the timing being advanced and retarded hydraulically through the crankshaft anyway?

I don't know what to do and it seems to be getting worse after the engine warms up.
February 12, 2013.

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