the solenoids work the oil flow to the lifter. those 4 cycl have lifters that are differant than the none mds cycl.

the lifter has a bleed hole in it. basicly it dropp pressure. craks the exhaust valve open and will not open the intake valve.

i suggest replacing the lifters to that cycl. also replace the solenoid to the cyl.

check that the motor is running the 0-20 oil also. anything greater in viscosity and the mds solenoid will not work right. but that does not explain why the others are not acting up.

is it setting codes? p0300? p0304?

steve