Obd 2 code reads p 15 18. There is no code number to relate to the problem. Do you have the answer? [ check engine light on 1999 ford taurus]

Code p1518= intake manifold runner control (IMRC) malfunction (stuck open)

the intake manifold has two runners per cylinder, feeding each of the cylinder heads
the IMRC assemblies are located between the intake manifold and two air passages for each cylinder.
one air passage is always open and the other passage switches from means of a valve plate.
below 3000 rpm, this valve plate is closed to improve low speed performance.
above 3000 rpm, this valve plate opens to improve high-speed exceleration.
the valve plates are opened and closed by the IMRC deactivation by the powertrain control module
(pcm) if your car or truck is not affected by the error code, the pcm may need to be reprogrammed
so that the error does not come up again. or you can connect an obd2 scanner and reset ever y time
it comes up. good luck!