I had the same problem exactly with my
high mileage 89 Lincoln LSC w/5.0 HO.
Turned out the EGR wasn't plugged, but
was worn (?) which caused it to stick shut
when cold - not enuf vacuum - took lots of
vacuum to pop it open. When warm, the car
started & idled fine. New EGR fixed.
Then, 20k miles later, started doing the
same thing. This time was the EGR position
indicator (piggybacked on the EGR). New
one fixed again. Now, mine is still
speed density, so don't know for sure if
same thing on a mass air.
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