1999 7.4 MPI New long block from Michigan Motorz. Engine runs rough at idle. Only have 10" of vacuum. When hot if you rev to > 2k and pull back to idle it will stall. You have to restart by opening throttle 3/4 or more. When cold it does not stall. Engine does not stall at any other time. Hole shot is fine and cruise is fine. WOT is 4300 whenboat loaded. Computer shows no faults or errors. New MAP sensor new TPS new fuel regulator. Replaced ECM with reman although by the way the unit came and how it was packaged it looks more like the core return. When you increase rpm to 1600 I have 16"of vacuum. No vacuum leaks pressure tested. If you pump up the vacuum to 18" engine runs normally. The next thing on our list is to replace the ICM.
Question would a bad ICM cause these symptoms we are seeing? The thinking is if the ICM does not tell the ECM that the engine is running then timing would not advance.
Cheers
John
Question would a bad ICM cause these symptoms we are seeing? The thinking is if the ICM does not tell the ECM that the engine is running then timing would not advance.
Cheers
John