Mercruiser 454 RPM

[ronbeckson]

"I have 454 Horizon,the rpms g

"I have 454 Horizon,the rpms go up and down between 1000 & 1300 in a looping action,under 1000& over 1300 are fine.Anyone know whats wrong?"

 

[Fun Times]

Dose this do this at idle or j

Dose this do this at idle or just off idle???

 

[guyjg]

What year? MPI? Maybe might

What year? MPI? Maybe might be computer temp. sender or IAC motor gummed up.

 

[ronbeckson]

Boat Tech -- Just off idle

Boat Tech -- Just off idle

 

[ronbeckson]

Guy -- 1999 horizon cross ram

Guy -- 1999 horizon cross ram MPI

 

[guyjg]

The coolant temp. sensor is on

The coolant temp. sensor is on the T'stat hsg. The hsg. gasket has two small continuity buttons in it to complete the eletrical circuit ground. If it is corroded that could be part of the problem. Does the temp gauge read correctly all the time?

Cleaning the throttle body (TB) bore and thottle plate will improve idle. Use THROTTLE BODY CLEANER and not carb cleaner. Check all the electrial connections on the TB.

 

[ronbeckson]

Guy -- temp guage reads correc

Guy -- temp guage reads correctly all the time.

 

[guyjg]

Try cleaning the TB. Test the

Try cleaning the TB. Test the TPS (Throttle Position Sensor) w/a digital VM for a dead spot.