5.7 EFI cold start Idle issue

Ricky R

New Member
Feb 2, 2019
1
Queens NY
Boat Info
290 Sundancer 1998 Garmin 741's
Engines
Merc 5.7 's Alpha Gen II Drives
Have well tuned 5.7 Merc EFI Alpha Gen II. Engine will not idle until it warms up. Need to race it at 2k+ until temp is up to 130 degrees before I can bring it down to idle then it is fine. Have installed new Idle control valve to no avail then I switched it with the one from the other engine still have same problem. All ICV's work fine with other engine. Any thoughts ?
Thanks
 
Temp sensor on the t-stat housing. Can be ohm'd at diff. temps to see if it is sending the correct info to the ecm
 

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