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View Full Version : 1998 225 efi merc shakes hard at idle



Trevor650
08-17-2017, 06:42 AM
She shakes at idle, ( like missing a cylinder but all are sparking with spark tester) in the higher rpm no real issue. But something has changed I have swapped everything from starboard to port all coils, computers,alternator,Cps,stator, checked thermostat and swapped temp sensors and complete plentems with vts. ( thought maybe higher pressure fuel pump so changed it,no change sent injectors out to be cleaned both motors) tps and map sensor reads within spec. The reeds looked fine ( looked twice but did not remove them off motor, maybe I need to pull them to see them from the other side. Fuel separators and vts and injectors screens are new. I did pull the hose off the low pressure fuel pump and pump with ball to see it there was a hole in diaphragm but it did not allow fuel to pass thru it. Only thing I can think of is wiring harness but all that looks really good. Motor is pre mix 511 hours on motors. Compression is the same on every cylinder. Motor serial 0g680728. Any thoughts!! Thank you in advance helping me.

XstreamVking
08-17-2017, 07:05 AM
Fire it up at night and see if any plug wires are arcing. Just a wag.....Might be something this simple.

Trevor650
08-17-2017, 07:52 AM
Will do,





Fire it up at night and see if any plug wires are arcing. Just a wag.....Might be something this simple.

ghost28
08-17-2017, 08:02 AM
If it still has the stock steel reeds in it pull em and change em to CCMS reeds....the steel ones love to chip, break, snap etc.....