Rough Idle after each run

IAC ( idle air controll ) sensor....

or so im being told...could just be
cleaned out..have to give it a try.
 
Buy a service manual. Check the resistance of the coolant temp sensor hot and cold. Most temperature sensors are 2 wire and easy to check. Set your multimeter to ohms. I would definitely seafoom it too. Might be supprised by the can mechanic. Start with the easy stuff first. Good luck.
Viking
 

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1marko said:
IAC ( idle air controll ) sensor....

or so im being told...could just be
cleaned out..have to give it a try.
Click to expand...

May be the IAC.. Incase you haven't located the IAC yet, it’s on the port side and it’s the unit which sucks in puffs of air. When you cover the air inlet, you should feel suction and notice your motors idle rpm change atleast momentarily. There isn't much to clean on the iac and if it is the issue, likely just need to change it. Wouldn’t waste much time there.

Some other areas I’d check are plugs and plug gaps, and plug wires. I’d thought that was my issue as well but plugs worked even though they were in rough shape. Plugs are fairly easy to pull and need changing or cleaning every so often. To identify if a shorted plug wire, I pulled each plug wire one at a time to see. If the rough idle gets worse, than that’s likely your problem wire or atleast problem cyclinder.
 
Might be worth having the injectors checked, I had a 2005 90hp Johnson that would develop a low speed and intermittent high speed miss . It was being caused by water collecting at the bottom of the fuel rail pitting the adjacent injector nozzle fouling the spray pattern.
 
donnie d said:
Maybe not the right place for this question, but somewhat related.

Anyone use Yamalubes Ring Free product in their fuel? Is this snake oil or does it actually work? I have heard it can really clean out any gummed up residues causing poor performance.

Guessing this wouldn’t help with this issue above but I noticed some seafoam comments and thought I’d ask about ring free. Thx
Click to expand...
We use Ring Free, in an F115, as recommended by Yamaha. It definitely works. We had a rough running motor that 1 bottle fixed. Now we use it regularly.
 
Foxsea said:
We use Ring Free, in an F115, as recommended by Yamaha. It definitely works. We had a rough running motor that 1 bottle fixed. Now we use it regularly.
Click to expand...

Thanks for that. I did end up grabbing a bottle and threw it in my fuel as recommended for the volume of fuel in my tank. Not sure if I can tell the difference, but will likely run it regularly given the reviews I’ve read since posting the question!
 
Looking at buying a new idle air control sensor but that's 150 plus taxes.
can these be cleaned. ? Going on line they appear to be a common consumable.
 
Yeah I was going to suggest the IAC one I read through and noticed it's efi. You should get it checked for codes and see if it functions properly. You may be wasting money for nothing if the valve is fine. Can't speak for Mercs but in Yamaha diagnostics you can do an active test on the trailer that tries all the different iac valve positions to make sure it works right. Get a fuel pressure gauge and check your high pressure circuit to make sure your injector pump is doing it's job, and also to make sure the fuel pressure regulator is doing it's as well. If the regulator is defective the ECU may not be compensating properly, causing the rough idling.
 
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Well that wasn't it. Looks like there are
A few things on the list..
Does anyone have a fuel pressure
gauge...?
 
1marko said:
Well that wasn't it. Looks like there are
A few things on the list..
Does anyone have a fuel pressure
gauge...?
Click to expand...
On my Merc - Its just a schrader style fitting.. You can get greenline hose to put a 100lb gauge and schrader male fitting together for like 15 $.. instant fuel pressure gauge.
 
My motor ran rough at idle. Ended up replacing all four coils and it runs smooth! My guess if you dont have fuel issues. Also, they are like 35 us each from amazon, or like 150$ from bridgeview. Good luck!
 
Start with the simple stuff first. With insulated plyers made for this job, pull a spark plug wire off the plug one at a time with the engine idling. If you pull one off and the motor runs worse...you know that one is working. If you pull one off and there is no change...it isn't firing and you have isolated it to that cylinder or that coil, or that injector.
 
I am keying in on the fuel system. I ve had these odd hiccups in the past but appear
To get worse over time. Becoming a PITFA.
I'm now taking a hard look at the vapor trap and low pressure pump.
So I would be able to screw any air pump
Up to this that has a shreader valve.?
The motor runs fine at first then slowly
Gets worse as the day progresses.
Got to be a dirt / pressure thing and
Appears to be a common issue.

600 hours now and otherwise been
A great addition
 
So here s a question. Who here regularly
Drains their trap. For some reason I was thinking like a fridge the water is allowed to evaporate on it's own..
 
profisher said:
Start with the simple stuff first. With insulated plyers made for this job, pull a spark plug wire off the plug one at a time with the engine idling. If you pull one off and the motor runs worse...you know that one is working. If you pull one off and there is no change...it isn't firing and you have isolated it to that cylinder or that coil, or that injector.
Click to expand...
In my case. The coils still fired.. just not as strong? Id guess. They still all worked. But idle was lumpy. Fine at speed.
 
1marko said:
I am keying in on the fuel system. I ve had these odd hiccups in the past but appear
To get worse over time. Becoming a PITFA.
I'm now taking a hard look at the vapor trap and low pressure pump.
So I would be able to screw any air pump
Up to this that has a shreader valve.?
The motor runs fine at first then slowly
Gets worse as the day progresses.
Got to be a dirt / pressure thing and
Appears to be a common issue.

600 hours now and otherwise been
A great addition
Click to expand...

Low pressure pump is more of a run/not run thing. The high pressure pump may be getting hot/acting up once its warm.

You can attach an air pressure guage to the scrader valve to verify fuel pressure
 
20190515_175548.jpg 20190515_175548.jpg So did a little investigating on my own before I lash out any more of my hard earned coin . Set out with a high pressure
Shock pump and ran the outboard
In the driveway...kicked the rpm
Up to 1500 then waited for it to warm
Up to operating temp...
The fuel pressure was bang on 44 lbs
That's a good sign. I also drained what
Was in the res prior to.
Soon after stated to hear the studdering.
With the hood off. I tried to see where the
Sound was coming from....

Upon closer inspection noticed this...wtf.!

Not only is one head bolt backed all the way out...I'm missing one entirely..
SCORE..!
now to the hesitation..

20190515_180219.jpg

Small whole were the high tension
Lead was sitting on a pointy part
Of the block.

Score # 2..

Start it up...issues gone.
For now...lol
 
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