Rough idle troubleshooting
Thread Starter
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Cruiser
Joined: Aug 2012
Posts: 130
Likes: 26
From: West Michigan
Rough idle troubleshooting
Hi all-
I have a 2012 FLHTK with 150,000 miles on it (75,000 on engine itself) that has developed a very rough idle. Have replaced the plugs and plug wires, fresh air cleaner, ran Techron fuel system cleaner through the fuel system via adding it to the fuel and used a Seafoam product sprayed into the air intake of the throttle body to clean the air supply side, throttle body etc. Spray cleaned the sensor in the throttle body also.
Rough idle remains. Interestingly it seems (by ear) to run fine for the first couple of minutes after cold startup, but once warmed up it acts like it wants to stall and sounds like it's missing and stumbling badly. It's not fuel, it has been going on for the last 1000 miles or so.
I talked to the service rep at my dealership and he suggested starting with the electrical wires that attach to the fuel injectors. He says they do fail. This is a failure that I have never heard of.
Questions-
Is that a legitimate place to go next? Are those wires prone to failure? If that is the problem, do they need to be replaced with identical wires or can they be field repaired?
What else could typically be going on to cause rough idle?
All ideas appreciated. I'm a decent mechanic but this is my first Harley and my first experience with EFI.
Thanks!
Glenn
I have a 2012 FLHTK with 150,000 miles on it (75,000 on engine itself) that has developed a very rough idle. Have replaced the plugs and plug wires, fresh air cleaner, ran Techron fuel system cleaner through the fuel system via adding it to the fuel and used a Seafoam product sprayed into the air intake of the throttle body to clean the air supply side, throttle body etc. Spray cleaned the sensor in the throttle body also.
Rough idle remains. Interestingly it seems (by ear) to run fine for the first couple of minutes after cold startup, but once warmed up it acts like it wants to stall and sounds like it's missing and stumbling badly. It's not fuel, it has been going on for the last 1000 miles or so.
I talked to the service rep at my dealership and he suggested starting with the electrical wires that attach to the fuel injectors. He says they do fail. This is a failure that I have never heard of.
Questions-
Is that a legitimate place to go next? Are those wires prone to failure? If that is the problem, do they need to be replaced with identical wires or can they be field repaired?
What else could typically be going on to cause rough idle?
All ideas appreciated. I'm a decent mechanic but this is my first Harley and my first experience with EFI.
Thanks!
Glenn
Last edited by GlennJ; Oct 29, 2022 at 10:56 AM. Reason: Supply more detailed information of efforts so far
Thread Starter
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Cruiser
Joined: Aug 2012
Posts: 130
Likes: 26
From: West Michigan
Thread Starter
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Cruiser
Joined: Aug 2012
Posts: 130
Likes: 26
From: West Michigan
OK Thanks.
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Thread Starter
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Cruiser
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From: West Michigan
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From: Canada Flats
Could also be a bad crank sensor or temp sensor , have seen some go without throwing a code , check the connections first before replacing them , cheap enough to replace . I try not to get into the habbit of throwing money at parts , but sometimes it's worth the gamble .
If I'm not mistaken , the 12 does not have an IAC valve , but cleaning the map sensor and throttle body / butterfly was a good idea .
You mentioned your bike ran well at cold start , but ran rough after it warmed up , makes me think temp sensor . Just a guess here .
Another thing , when was the last time you were in the tank ? Dirty fuel filter , bad pressure regulator etc , filter should be changed every 25K .
If I'm not mistaken , the 12 does not have an IAC valve , but cleaning the map sensor and throttle body / butterfly was a good idea .
You mentioned your bike ran well at cold start , but ran rough after it warmed up , makes me think temp sensor . Just a guess here .
Another thing , when was the last time you were in the tank ? Dirty fuel filter , bad pressure regulator etc , filter should be changed every 25K .
Last edited by MyFavRk; Oct 30, 2022 at 11:32 AM.