Bad cough/ miss at idle.

[Ranger 330V]

1978 140hp Johnson. 100psi compression all the way around. New stator, trigger, powerpacks, rectifier, plugs. Old green coils. She runs great when you "run" her. At idle is the problem...sometimes she does it sometimes she doesn't. There is a bad cough that comes and goes. To the point that it will die. When at first start up its really bad and as the engine gets warmed up its not quite as bad but will start after a time. I'm thinking idles jets because once you start running its fine. The engine sat for 2 1/2 years before I got it. Runs fine other than that. Plugs are nice and light brown...all look the same. I have decarbed also. Could the old green coils cause this?? I'm going to eventually replace them but do not have funds right now. I am also going to rebuild carbs this later when it actually gets cold. Its a pretty good cough...will actually jerk the steering will sometimes. Could it be reeds?? Could I get it idling and spray seafoam in each venturi and see if the stumble goes away or gets better?? That would probably tell me if it was fuel related?? Ask anything else if I missed something in my information. Thanks alot!!

 

[flabum]

Re: Bad cough/ miss at idle.

Two things to start with:
1) With the engine sitting for so long, you should take the carbs off and clean them out well. Get a couple carb kits and some engine tuner. The engine tuner does a nice job of cleaning carbs....let them soak 1/2 hour with the engine tuner. The carb passages probably has some varnish in them from sitting so long.

2) Idle timing. Should be about 4 degrees after TDC.

 

[DJ]

Re: Bad cough/ miss at idle.

Two things to start with:
1) With the engine sitting for so long, you should take the carbs off and clean them out well. Get a couple carb kits and some engine tuner. The engine tuner does a nice job of cleaning carbs....let them soak 1/2 hour with the engine tuner. The carb passages probably has some varnish in them from sitting so long.

.

Agreed. What you are describing is a "lean sneeze". Lean is not good.

 

[Ranger 330V]

Re: Bad cough/ miss at idle.

thats what I thought...timing is set...link and sync when I put the new electronics on. I'll rebuild carbs. Who makes the best?? I have heard sierra isn't the best product to use...is this true?? And what are the jet sizes for this engine?? My manual probably states this but I figures someone knows it off the top of their head...I'd like to check and make sure they are right while I have it apart...the powerhead has been rebuilt and I'd hate to rebuild and put back together and have the wrong jets..never know what some people will do. Got this engine at a bargin..lol Thanks alot

 

[DJ]

Re: Bad cough/ miss at idle.

thats what I thought...timing is set...link and sync when I put the new electronics on. I'll rebuild carbs. Who makes the best?? I have heard sierra isn't the best product to use...is this true?? And what are the jet sizes for this engine?? My manual probably states this but I figures someone knows it off the top of their head...I'd like to check and make sure they are right while I have it apart...the powerhead has been rebuilt and I'd hate to rebuild and put back together and have the wrong jets..never know what some people will do. Got this engine at a bargin..lol Thanks alot

Don't wait too long. As stated: lean=bad. Waiting may leave you with a pile of scrap. Park it until you can get everything you need to go completely through it. Once done you can mess with props all you want.

 

[guy74]

Re: Bad cough/ miss at idle.

One thing that I might reccomend before you take the carbs off to rebuild them is to run it on the muffs and spray some deepcreep or wd 40 around the tops of the carbs to check for air leaks into the idle circuit. I had a lean sneaze problem on my 100xp and it was an idle cavity cover gasket leaking. I think if it were mine I'd check for an air leak like that before I took it apart, is alot easier to fix while you are reuilding the carbs. Also, take the air box off and start it up, take your finger and cover up the idle air bleeds in the top of the carb throats one at a time. You will probably find one of them, that when you cover it with your finger, makes the motor smooth out. If you do this before you take it apart you will know where to consentrate you search for a problem while you rebuild the carbs. Hope you have good luck getting it running good.
Brian

 

[Ranger 330V]

Re: Bad cough/ miss at idle.

thanks guy...thats a great point..I'll do that!

 

[flabum]

Re: Bad cough/ miss at idle.

One thing that I might reccomend before you take the carbs off to rebuild them is to run it on the muffs and spray some deepcreep or wd 40 around the tops of the carbs to check for air leaks into the idle circuit. I had a lean sneaze problem on my 100xp and it was an idle cavity cover gasket leaking. I think if it were mine I'd check for an air leak like that before I took it apart, is alot easier to fix while you are reuilding the carbs. Also, take the air box off and start it up, take your finger and cover up the idle air bleeds in the top of the carb throats one at a time. You will probably find one of them, that when you cover it with your finger, makes the motor smooth out. If you do this before you take it apart you will know where to consentrate you search for a problem while you rebuild the carbs. Hope you have good luck getting it running good.
Brian

His carbs don't have those covers on them, his has the welch plugs that will be chaged during rebuild anyhow.

I don't see any need to look for carb leaks if your'e going to do a proper job to begin with.

One thing to check however, is the throttle shafts. Check them for excessive play. They will move a bit, but not much. It's hard to describe how much is too much, but if the play causes the butterfly to bind comming off idle, then they have too much play.

 

[guy74]

Re: Bad cough/ miss at idle.

Yes I know his carbs don't have the covers, but they do have lead shot plugs which can also leak air into the idle circuit. I know that I have replaced a set of older carbs with newer ones on one of the motor I work on, so I wouldn't take it for granted which carbs are on a 29 year old motor.
Brian

 

[Ranger 330V]

Re: Bad cough/ miss at idle.

I have checked the throttle plates and shafts and they don't have any play in them. My choke does however have quite a bit of play in it...but the choke shouldn't have anything to with it as they will be open anyways. Yes I am going to do a complete overhaul and soaking of the carbs...I'll pay close attention to plugs. THanks!! What carb kits do you guys use?

 

[BillP]

Re: Bad cough/ miss at idle.

Those EXACT symptoms happened to me on a 1980 140 omc. It had nothing to do with carbs. The %$#!@#X! dealer removed the tstat gutts instead of changing them. It sneezed, coughed, stopped, etc. at idle without them and was a little better when warm. Otherwise it ran like a new motor should. This was in Florida where the water temp was 80+F yr round.

bp

 

[Ranger 330V]

Re: Bad cough/ miss at idle.

that is a possiblity..I have not checked to see if the stats have been pulled or not. It does get better as you warm up but still does it at times...it doesn't do it all the time. after you run hard its fine..then if you let it sit and idle for a minute or so it will start it...I'm going to rebuild the carbs anyways for piece of mind...but if that does cure it I will look for stats...guess it could be that it never warms up and when it does it cools back down quickly...it was pretty bad this weekend in 55 degree water. THanks for your response! Another rock to turn over is always good. I'm going to rebuild cooling system this winter also...so I'll check those out.

 

[Silvertip]

Re: Bad cough/ miss at idle.

Spraying cleaning agents through the carb throat only cleans the carb throat. The mixture needs to pass through the carb internals and the only way to do that is throught the fuel line using a concentrated mixture in a separate tank. I agree though, do the rebuild.

 

[flabum]

Re: Bad cough/ miss at idle.

The stats are a bear to get to especially if there is corrosion. You can gain a little more access by removing the lower wrap around shroud then unbolting the pan to let it drop some. But we will get to that when you do the stats.

 

[BillP]

Re: Bad cough/ miss at idle.

Yep, the tstats are difficult to get at on that one. Are your plugs showing lean or rich?

 

[flabum]

Re: Bad cough/ miss at idle.

Yep, the tstats are difficult to get at on that one. Are your plugs showing lean or rich?

Plugs are nice and light brown...all look the same.

Looks good to me

 

[guy74]

Re: Bad cough/ miss at idle.

The last set aof thermostats I changed on a motor like yours was on a 1981 90hp evinrude. The bolts were corroded in very bad, the boat had been used in salt water in western Kansas. Anyway it's my cousin's boat and he had already rounded the corners off the bolt heads, so I removed the bolt heads with a carbide burr on a dremel tool. With the heads gone it was easier to get penatrating oil into the bolts where they go though the thermastat housing. I was able to slide the housing off after a couple days, then the bolts turned out of their threads without a problem. I dropped the bac of the lower cowling down to give me a little more room. I hope you don't run into these kind of problems, but the ket to getting those kind of things apart is patience.
Goodday,
Brian