Uneven Idle -- Stick Coils?

[roger 04 rt]

Yesterday after an hour ride I noticed that my idle was uneven and a little low--the sound was something like a barely audible blub blub blub instead of hmmmmm. I'm in the middle of some fueling experiments so of course I assumed that was the issue so I changed the configuration back to the last known good, reset the Motronic, went for a half hour ride. Same thing upon return.

 

Luckily I've got my AFR gauge attached all the time (Wideband O2) so I connected it to my computer, along with the GS-911. No GS-911 errors and the sensors all looked good. The O2 plot was correct and nicely centered around 13.8:1. Hot idle with the Cold Start lever up was 1300 (usually 1500) and regular idle was 950-1000 (usually 1100).

 

At this point my suspicion turned to the stick coils. Very carefully, I pulled the connector from the right stick coil. Big RPM drop--then reconnnected. Next I gently slid the left connector off the stick coil, a drop, but not as big as the right side--then reconnected and the idle came up to normal levels for both regular and fast idle.

 

The condition had persisted for two hours of riding and now is gone. I know that I didn't move the stick coils at all so at the moment, I'm thinking the connection to the right coil had built up some resistance.

 

Then I came across this in another thread.

 

Morning Troy

... Other things to check is that the little ground wire is hooked up & making good contact to the L/H TB bottom. ...

 

So my questions are:

 

--Does situation sound like a stick coil that's about to go, or just a bad connection problem?

 

--What is special about the ground on the left hand stick coil/ throttle body?

 

Thanks for any suggestions,

RB

[GroceryRun]

I guess the easiest thing to do at the moment would be to clean

the left side ground terminal. But since it's so easy to do, I'd do

the right side also.

 

I can see a stick coil on your future shopping list.

[JamesW]

Hello again Roger,

I had a stick coil problem early on and it is very difficult to diagnose a faulty stick coil I think because of the presence of the secondary spark plugs on the '04. Best way to diagnose the problem is to have a spare stick coil handy. Also, it would be easy if the stick coil would just completely fail rather than become weak or even intermittent. I think the stick coils are effected by either excessive heat or maybe moisture invasion.

 

Wow, you do have your issues with that '04 of yours. Could there be a Honda in your future?

[dirtrider]

Afternoon Roger

 

I think that TB ground wire is to bleed off static voltage rebuild up in that rubber isolated L/H TB. Any stray static voltage in the TPS sensor (it sees a redundant low through one of the retention screws) could effect the fueling computer TPS input.

 

On your (possible) stick coil issue. A bad stick coil usually shows up at riding engine load before idle but that is no guarantee. As a rule when a stick goes it starts arcing internally to the RFI shielding so acts up under high engine load first.

 

I'm not sure what caused your idling problem but maybe as simple as a speck of carbon in the spark plug or a trace down the center electrode porcelain. Or maybe even a spec of carbon trapped between a valve & valve seat.

 

Personally, first thing I would do is replace (of swap) the spark plug for that coil then ride the bike for a while to see if the problem comes back.

 

If your problem still persists then swap the upper coils side to side to see if the idling problem follows the coil to the other side.

 

[roger 04 rt]

Thanks everyone and DR. For now, merely seating and unseating the stick coil connector eliminated the issue. With all intermittent problems, time will tell.

[roger 04 rt]

Hello again Roger,

I had a stick coil problem early on and it is very difficult to diagnose a faulty stick coil I think because of the presence of the secondary spark plugs on the '04. Best way to diagnose the problem is to have a spare stick coil handy. Also, it would be easy if the stick coil would just completely fail rather than become weak or even intermittent. I think the stick coils are effected by either excessive heat or maybe moisture invasion.

 

Wow, you do have your issues with that '04 of yours. Could there be a Honda in your future?

 

Hey JamesW, I'll get a spare at some point. I don't really have any issues at the moment but boy do I like to experiment. RB

[JamesW]

Hey Roger,

I was only half kidding about the Honda MC. I just bought a new Honda walk behind lawn mower and WOW! Over head cam one cylinder motor with auto choke that starts with one pull and runs smooth as silk, full mulch or bag by just moving a lever, blade brake, on and on... If they build motorcycles this good.. WOWZER!! I can just see BMW building lawn mowers. I definitely positively wouldn't buy one. Oh, now what would make me say that?

[realshelby]

Roger, one of the biggest headaches I have had on a motorcycle was caused by stick coils! My '04 now has 2 new stick coils and my headaches are gone. Bad stick coils will show a spark ( pull the wire off and put an extra spark plug in it while engine runs on secondary plug) when checked outside of engine. Like Dirtrider says, they just don't fire correctly under load. On the stand with engine at 3000 rpm I could pull the plug wire off the secondary plug and the engine would falter badly. The other side would only show a small change in engine sound. That is what made me buy the first new one...the second one failed about a year later.

[roger 04 rt]

Terry, Many thanks for that info. Given the age of the motorcycle, as with the gas tank/pump/filter/hose overhaul, I'm thinking that the coils are a weak spot and sometime soon I'll just replace them both.

 

I'm relatively new to the R1150RT, really enjoy riding it and want it to be reliable. This winter I'll probably replace the clutch circuit servo, check and lube the transmission splines and have a look at the engine seals. At that point I think I'll have a fairly well refurbished bike. RB