mid 80's 140hp Johnson misfire at idle????

[adm1476]

I have a mid 80's Johnson 140hp that has a misfire at idle. It runs out fine but runs poorly when idling. Just rebuilt the carbs due to water being in the fuel tank. Using a small portable tank with all fresh fuel now. Did compression test all good around 125psi. Plugs look fairly new. Also has 1 new coil. I'm thinking either another coil going bad or module. How do I test foe a bad coil? and how do i tell if the module is going bad?

 

[racerone]

Put a timing light on each lead to see if there is an ignition miss.

 

[flyingscott]

Put up a video are you sure it's not a lean sneeze

 

[adm1476]

How would I know if it was a lean sneeze?

 

[emdsapmgr]

What engine do you have? A looper or a crossflow? Pls post the model number. A lean sneeze is a term used for an engine which has an occasional miss at idle. Sort of a periodic cough every few rpm's. This is a carb problem not ignition. Is caused by a lean condition in the carbs. Once the idle passages get restricted from dried fuel over the years, the passages won't flow enough fuel and the engine will "miss" every few rpm's. If this is what you are experiencing, the fix is to completely tear down the carbs and clean them thoroughly with a product that will dissolve dried fuel gelatin.

 

[adm1476]

It is not a lean sneeze. I just rebuilt the carbs completely. It is a misfire for sure. I am going to try new plugs today. The fuel tank had lots of water in it, that is why I just rebuilt the carbs.

 

[emdsapmgr]

What model are you working on?

 

[adm1476]

I believe it is a looper. It is not my boat, It is at a friend of mine's house, so I cant tell you what the exact model number is.

 

[racerone]

Are there 2 carburetors or 4 seperate plastic carburetors ?