Rough idle

[Hank in WV]

I know this has been asked before, but I can't find it. I have a 2010 RT with 85000 miles. It has been idling quite rough for awhile. Above idle it runs just fine. The bottom right plug is dirty (new at 80000). Tried several different plugs with no change. All plugs fired when grounded on the outside of the engine. Even tried a TPS relearn with no effect. Am I looking at a new stick coil? Thanks in advance for any help.

[dirtrider]

14 hours ago, Hank in WV said:

I know this has been asked before, but I can't find it. I have a 2010 RT with 85000 miles. It has been idling quite rough for awhile. Above idle it runs just fine. The bottom right plug is dirty (new at 80000). Tried several different plugs with no change. All plugs fired when grounded on the outside of the engine. Even tried a TPS relearn with no effect. Am I looking at a new stick coil? Thanks in advance for any help.

Evening Hank

 

It could be a lower stick coil, it takes more KV to fire a spark plug under compression than out in the open air.

 

You might see if it will idle on both sides with the upper stick coils disconnected (probably need to hold the throttle open slightly to make it idle on just the lowers). See if both side exhaust pipes get hot running on only the lower plugs.  

 

Probably not an upper stick coil problem as they usually  don't run very good at road load speed with an upper malfunctioning.

 

But don't get single tracked on just a stick coil issue as other things could be causing your issues like a leaking valve or fuel injector issue. 

 

I worked on a hexhead earlier this year that had been to a couple of shops for a poor / rough idle with nothing found. After it came to me I finally tracked it down to way too much fuel additive (Sea Foam & Techron mixed)  in the fuel. Fresh fuel & it idled great.

 

 

 

 

[Hank in WV]

Thanks dirtrider, I'll try that tomorrow.

[Hank in WV]

I disconnected the top plugs and was shocked on hao well it started and idled with no throttle.

[dirtrider]

5 minutes ago, Hank in WV said:

I disconnected the top plugs and was shocked on hao well it started and idled with no throttle.

Morning Hank

 

Then it doesn't blatantly sound like you have a failed lower stick coil. 

 

Try the same test by disconnecting  the lowers then see if it will run it on just the uppers. (again see if the pipes get to about the same temp).  

[Hank in WV]

Tried that with the same results.

[dirtrider]

20 minutes ago, Hank in WV said:

Tried that with the same results.

Afternoon Hank

 

Then you have some other problem causing that rough idle.

 

With a little more info from you maybe we help you track it down a little closer.

 

When did the problem Start? 

 

Did it appear all of a sudden of come on slowly? 

 

Any type of service or other work done on that motorcycle just before the problem started? 

 

Any other details that you can add? 

 

Is your Evap system purge hose connected to the R/H throttle body vacuum nipple, if so maybe try disconnecting that & plugging off the vacuum  nipple as a test to see if it then idles better (give it a  little run time after the hose disconnect before judging)   

 

 

[Hank in WV]

The problem seemed to come on slowly. I haven't done anything to the bike since last winter. The only vacuum nipple I could find was on the right side body but I'm assuming we're talking about the same thing. After warming it up for about ten minutes, I took the hose off and when I blocked the nipple, it seemed to smooth out quite a bit. If this is the issue, what would be my next step. I'm kind of lost on these modern bikes. I started off riding on a 56 Tri Tbird.

[dirtrider]

12 minutes ago, Hank in WV said:

The problem seemed to come on slowly. I haven't done anything to the bike since last winter. The only vacuum nipple I could find was on the right side body but I'm assuming we're talking about the same thing. After warming it up for about ten minutes, I took the hose off and when I blocked the nipple, it seemed to smooth out quite a bit. If this is the issue, what would be my next step. I'm kind of lost on these modern bikes. I started off riding on a 56 Tri Tbird.

Afternoon Hank 

 

If it idles better with the hose removed & vacuum nipple plugged that sort of points to a saturated Evap canister (fuel logged) carbon media. (try to determine if the hose unplugging  really is  helping the idle)

 

Do you typically overfill the fuel tank then park the motorcycle?  If so then don't do that. 

 

You can ride it for a while with that hose disconnected as a test, if that helps the idle then we will have to try to determine if the Evap canister is permanently damaged or if you can save it  by just riding the motorcycle with a less than full tank & allow the natural purging to clear the fuel from the  Evap can.
 

[Hank in WV]

dr, I think I might have found the problem. I traced that hose to the other end and it was connected to nothing. As soon as I hooked it up, the idle smoothed considerably. Here's hoping that's the problem. I have to put it all back together to take it for a ride. I sure do appreciate all your help d r. You're pretty amazing with all your knowledge and logic. Thank you.