we have a couple of brand new motors like this, our problem is that the stbd motor idle is oscilating between 900 & 2000 rpm, ...can somebody help us please..

Any trouble codes? My first thoughts would be TPS or MAP sensors, but it could be other things. Hard to tell with limited info given.

Dave

Might have the idle control valve sticking. Should be easy enough to pull it and clean it to start.

my 502 mpi did the same thing. I replaced the IAC valve, reset the TPS to 0% at idle and set the IAC to 35-40 counts. That cleared it up and it idles fine now. I may have been able to get away with just cleaning the IAC but it wasthe original valve with about 450 hours and a new one was only $75. Hope that helps. MJB

if the motors are fuel inj. check the idle sensor on the throttle body