350 5.7 EFIs Lose RPM Under Electrical Load

[sarnone]

Hello, I have a 1998 formula with twin 5.7 medics that are efi. While at idle, if there is an added electrical load like trim or outdrives, both engines lose 100-200 rpms. Let go on the outdrives or tabs and rpms are restored. I also wondered if it was related to engines dying in gear before the engines were fully warmed up. Thanks for any help.

 

[Bondo]

Ayuh,..... Welcome Aboard,.... My 1st guess is a Bad Ground,.....

Clean both battery cables on both ends to shiny metal clean, 'n try it,.....

 

[alldodge]

Are you having any problems after the motors are warmed up, including while running

 

[sarnone]

Thank you for the help. I will follow up with your recommendation...

 

[sarnone]

Alldodge, mostly at idle and close to idle. On plane speeds are okay. I think I might check connections at the alternators too. And on further trial it's only the outdrive trimming and lowering or raising one is not as bad as when both are moved.

 

[alldodge]

mostly at idle and close to idle

Could be electrical but could also be an issue with a sticking Idle Air Control (IAC) valve. From idle to a bit above it is where the IAC is controlling the motor. May need cleaning