Erratic idle

[penoe01]

I have a 1999 NS 18E2. When it is at idle the rpm will decrease below normal like 600 almost like it will cut off and then increase above normal 1500-2000 all on its own without touching the throttle. Does anyone have any ideas to what would cause this? Thank you.

 

[pvanv]

Re: Erratic idle

Could be a lot of things, but confirm that the carb is spotlessly clean, and no vacuum leaks, and fresh plugs are in.

 

[TOHATSU GURU]

Re: Erratic idle

Restricted fuel flow or intermittent fire to one cylinder.

 

[pvanv]

Re: Erratic idle

Yep. Considering that it has a siamese coil, the only way one plug would misfire is a bad plug or wire. Assuming the plugs are good, my money is on the fuel system.

 

[penoe01]

Re: Erratic idle

I have replaced the plugs, coil, fuel lines, fuel pump, fuel connectors, gas tank, and head gasket. Also had a dealer clean the carb and adjust it and still having the same issue.

 

[pvanv]

Re: Erratic idle

Why were all those parts changed? The pump is integral with the carb... what method was used to clean the carb? Is the float height correct? Was the float valve needle changed?