1991 Johnson 140hp misfires at idle in neutral

My outboard is missing in neutral at idle. It only does this after it gets warmed up. If you put it in gear it will quit misfiring. What is the cause of this? It idles at about 1200 rpm in neutral and about 1000rpm in gear. Im not really sure what it's supposed to idle at. I don't think idle speed has anything to do with it missing though. I already changed the plugs and decarboned it thinking that was the problem. I do it every 50hrs. Thanks!

Re: 1991 Johnson 140hp misfires at idle in neutral

does it kinda sound like a sneeze? if you bump the choke does it stop doing it for a second? if so carbs are dirty or your fuel lines have a leak somewhere
post your model number for us so we can give you more info

Re: 1991 Johnson 140hp misfires at idle in neutral

model number: VJ140LEID

The rpms raise slightly by maybe 20rpm and then it misses goes back down. The miss sounds more like a thud than a sneeze. It does this once about every 4 seconds. Im going to bump the rpm down slightly and see if that stops it. I had to readjust it after having the dealer replace the steering arm. They messed with the idle speed. Had it set too low and it would stall when shifting between gears. It's weird cause it was running just fine while I was adjusting the idle screw and then on the last turn of the screw it started missing. They had it running at like 700rpm which put it at around 600 or so in gear so it would stall. So I put it back to around 1200 where I had it before. Im going to put it down to 1100 since that should be an ok speed to prevent stalling while shifting gears. Mainly from forward into reverse. But what do you guys think anyways? Any ideas as to what is causing it? It runs fine throughout the entire rpm range just as long as you don't let it idle in neutral.

Re: 1991 Johnson 140hp misfires at idle in neutral

yeah your looking for 1100 in neutral on muffs when you put it in the water it should drop down to about 850-900 idling in neutral due to the back pressure from the water

there was another guy on here a couple of days ago with the same problem but he never posted back what was wrong (i and everyone else here hate that) so if and when you do come up with a solution post back as this seems to be a common problem with these motors
try checking your plugs though theyll indicate which cylinder is giving you trouble and you can adjust the carb, test that coil, and check the voltage out put to that cylinder from the power pack

Re: 1991 Johnson 140hp misfires at idle in neutral

An idle speed of 1200 or even 1000 is too high. If it takes that to make it run there is an old problem that needs to be addressed. If the idle jets are adjustable try that but it sounds like a different issue. Perhaps timing is not sync'd with the carbs perhaps dirty carbs or floats not set correctly. As always... a compression check precedes putting any money into it.

Re: 1991 Johnson 140hp misfires at idle in neutral

with all due respect sir imall have to pull rank on this one ... 1100 on the hose is absolutely 100% where the idle should be the backpressure will lower the rpm once its in the water to a lower and much more normal idle speed

Re: 1991 Johnson 140hp misfires at idle in neutral

I'll have to side with my Senior Chief Levi on this one. If 1100 is too much on muffs then my motor has been "screwed up" for a long time. If that's the case, please don't tell mine because she'll get all fussy then like she deserved to act out and missed an opportunity. She's already mad at me for not using her as much as I should be.

Re: 1991 Johnson 140hp misfires at idle in neutral

It's 1100rpm in the water in neutral and about 1000rpm in gear. So I seems like I have it about 100rpm too high. I didn't pay attention to what it was on the muffs. I think it was 200rpm higher. Let me ajust that set screw again and bump it down slightly since it didn't start missing until I got it up to 1100rpm when I adjusted it the first time. Hopefully if I back it down to around 900-1000 that will stop it. Sometimes engines run crappy at certain speeds under no load especially two strokes. I'll take the boat out in a few days and keep you guys updated on what happens. Thanks! Im still irritated that dealer messed with the idle and then didn't tell me. Im lucky I didn't hit another boat. Idle speed isn't usually something you set and just forget it takes a few tries to get it where it needs to be. Thanks again guys.

Re: 1991 Johnson 140hp misfires at idle in neutral

yeah if you go hook it up on the hose and set it to 1100 youll be SPOT ON when you put it the water