Stumbling Idle

[R1100S-Slick]

Good Day Fellow R1100S Owners!

Some time ago, (a long time ago) I posted my bikes poor above idle running issues (stumbling / Partial cutting out) I called it. I read in another BMW forum that one owner suggested trying pulling the lower plug off while the bike is running to test the Stick Coils on each cylinder.

Recently I have begun to re-diagnose this running problem. I haven't been able to give the bike the full attention it deserves till now. It has 42000 miles in it and I am suspicious of the stick coils acting up and misfiring at about 1200-1300 rpm just as I want to get on the throttle to drive away from a stop. Once underway at road speeds (any speed) it runs just fine. This rough (partial stalling) issue comes back again at what I call parking lot speed.

Today I started the bike and after a short warm up with the bike on the lower of the two fast idle notches I pulled the lower plug wire off the right cylinder and the bike sounded terrible and seemed to be running on one cylinder. When I reconnected the lower plug wire with the bike struggling to remain running a load bang was heard from the exhaust pipes. I assumed this was unburned fuel mixture when the right cylinder reignited the fuel air mixture.

The left cylinder behaved similarly when the lower plug wire was pulled away, but not to the extreme of the right cylinder. It too caused very poor idling on the high idle setting.

So it looks like my stick coils are toast. Just to add I have balanced both throttle bodies using the Twin Max device and have adjusted the idle mixture screws much earlier in the history of this bike and I am sure there are no issues with the throttles.

I also much earlier is the bikes' history replaced the stock Fuel Injectors with the rebalanced (improved) fuel injectors from Germany. I still have the stock ones and was surprised that the stock ones have the same four nozzle pattern as the socalled improved ones from Germany. Perhaps they are also to blame for the running issues with this bike?

Any suggestion here are well appreciated.
Thank You Guys,
Hans...

[908/930]

I have only single spark so no help there. Did you check the adjustment of the (TPS) throttle position sensor? That takes over fuel ratio when throttle is off idle.

[R1100S-Slick]

Thanks I'll check that as well....

[Groceryrun]

What year is the bike ? Are you the original owner ? Do the fuel injectors from Germany look like the retired "stock" fuel injectors ?

I would replace the stick coils.
Warning : The plastic electrical connector tab to the stick coils are very fragile, lift with care.

[wswartzwel]

Check the throttle body shafts for wear. The brass shafts wear and vibrate at low RPM This causes the TPS to be erratic just off idle. There are threads here on how to repair it.

[njsax]

Originally Posted by wswartzwel

Check the throttle body shafts for wear. The brass shafts wear and vibrate at low RPM This causes the TPS to be erratic just off idle. There are threads here on how to repair it.

I'll second this. Your mileage is about right for this service. Do you hear any rattling coming from the throttle bodies while the bike is idling? Use a listening rod like a dowel. Do this before buying new stick coils that you might not need.

[R1100S-Slick]

OK guys thanks very much for your responses...

I'll try the screwdriver listening idea for the throttle plate shaft wear issues. I am the second owner I purchased this bike used 6 years ago with 30,000 miles on it. The bike is an April 2004 build date. And of course the first thing I did after falling in love with it was to peruse the internet for 'upgrades'. Lol....

The symptoms I am relaying started about two years ago when I think about it. It was so minor I didn't pay any attention to it and it has gotten worse over the last two years to now being a problem.

[R1100S-Slick]

Originally Posted by Groceryrun

What year is the bike ? Are you the original owner ? Do the fuel injectors from Germany look like the retired "stock" fuel injectors ?

I would replace the stick coils.
Warning : The plastic electrical connector tab to the stick coils are very fragile, lift with care.

Hi Groceryrun, the German imported injectors have the same number of Nozzles in the bottom as the stock ones I took out. I kept the stock ones and my next move is to replace the injectors with the originals that were there when I bought the bike and try that configuration. I did go ahead the order new Stick Coils anyway as a backup option.

[sgoodwin]

I got the 1200 injector kit for my 1100S. Probably the best upgrade for running you can make. I have the Laser exhaust & chip & these injectors were a better & cheaper upgrade.

https://injector-rehab.com/product/1200gs-injector-upgrade-adapter-kit-for-1150-gs-1100s-new-injectors-included/

[R1100S-Slick]

Thanks for all the Responses. Lucky me it was the stick coils that were bad. The bike even idles better now off the high idle warm up lever. I even pulled the lower plugs off while running and still no change (degradation) of the idle! It seems to idle nicely now at about 1050 RPMs. Checked the plugs and they looked good as well.

Thanks Guys, I knew I could get good feedback here...

[R1100S-Slick]

This is a follow up on my idle situation I noted a higher than usual idle, at 1400-1500 when warmed up. I'm attempting to balance the throttle bodies using the TwinMax and adjusting the idle watching the BMW Guys Videos on you Tube.

I got it pretty close BUT I noted unexpected changes in the twin Max when the revs were held up near 3000 rpms (as per Video). I listened to the Throttle shafts using a Long screwdriver to my ear and placing it on the throttle bodies at about the throttle shaft locations, with the engine running at idle. There is a knack knack knack sound at that location of the throttle body with even louder same sound at the left throttle body.

Is this normal? Should I be hearing any sound at all, or should it be much more muted?

I have also been using a laser temp measuring device at the header pipe on each cylinder and the Left exhaust header is about 30 to 50 degrees higher than the Right exhaust header at idle usually (it does change at times).

Thanks for any feedback on this matter guys....

Slick....

[sgoodwin]

The sounds could be the injectors firing not the shafts rattling, but I can't hear it to tell you which. When I use the Twinmax, I dial down the pulses so I get a better reading & also hold at 4k instead of 3k. What weird readings did you get as mine stays pretty even all up & down the rev range. Idle is set with the air screws balanced & upper revs with the right cable, I never change the left cable as long as the throttle plate close fully, which it always has. As for temps I have no idea if they're the same or not as I never measured them, but if one side is hotter, I would assume it's leaner. This should all be done with the valves checked & adjusted first.

[R1100S-Slick]

OK Thanks sgoodwin..... I found that in my previous fiddling around I had inadvertently raised the idle through the high idle switch on the left handle bar, So now I have to rebalance again and reset the mixture screws.

I read somewhere else a while ago that 80% of a Bikes problems are owner created. Sounds like me too...Lol.

[brentw1]

the ticking is usually because the throttle cable has some tension so just back them both off so
you have some slack and the throttles are fully closed, then sync them so they pull open at the same time, I usually do this with the bike off, as you roll off the throttle you should hear one click.
not two, and if you are out of sync at 3000 you are not synced, they twinmax should show the same balance at all rpms, I have a electric balancer and actually ride them on the road under load
to check that the balance is correct all the way up.
this can be caused by lots of things, cable issues dirt in the cam etc.
also with the lower plugs pulled you should have some rpm drop

[R1100S-Slick]

Originally Posted by brentw1

the ticking is usually because the throttle cable has some tension so just back them both off so
you have some slack and the throttles are fully closed, then sync them so they pull open at the same time, I usually do this with the bike off, as you roll off the throttle you should hear one click.
not two, and if you are out of sync at 3000 you are not synced, they twinmax should show the same balance at all rpms, I have a electric balancer and actually ride them on the road under load
to check that the balance is correct all the way up.
this can be caused by lots of things, cable issues dirt in the cam etc.
also with the lower plugs pulled you should have some rpm drop

Hey Thanks for that feedback... I'll work on the points you brought up...

[mgp steve]

The problem probably isn’t fuel injectors BUT try adding 4 ounces of Chevron Techron to a tank of gas and riding 75-miles. Techron is magic. This might be all you need.

I just scanned the conversations and may have missed this part of the discussion: pulling plug wires on conventional coils while the bike is running is not good; the coil can be destroyed. The coil should be grounded before starting the bike. It was not clear if the lower plugs or the power to the coils buried in the frame of the S were pulled. Removing power to the coil is the best way to check to see if a plug is firing. ‘04-on 1100S’ have two, lower plug-coils, one for each lower plug so isolating an individual plug is possible.

The original center coils on 1100S twin sparks failed with regularity. The original, single spark to the center plug was a conventional, coil mounted on the bike’s frame sending high energy to the center-mounted plug. On twin sparks, the center plug’s coil is in the cap that attaches to the directly to the plug’s tip.

I went through six (twin spark) coils before BMW issued a superseded coil-fix. I currently have more than 140,000 miles on the superseded coils with no failures.

The other end of the coil (the spark plug end) is where the large voltage across the spark plug’s gap discharges.

Uncapping the plug downstream of the coil while running takes away the designed-in grounding (jumping from the spark plug’s center electrode to the plug’s grounded electrode(s). The stick coil will be damaged if pulled from the spark plug while running. You might get a nasty shock too if the hot coil grounds through you.

However the stick-coil-in-plug coil’s low energy wire can be pulled while the bike is running because as its name states; it is low voltage. Disconnecting here stops the energizing of the downstream coil.

This is where the center coil’s health should be checked. It’s very easy to do with the engine running at idle. The black plastic “Twin Spark” cover is a friction fit and pops off easily. On BCR’s the CF valve cover protector must be removed first.

Once the cover is removed the low energy lead can be slipped rearward off the coil by carefully lifting the tab securing it to the coil. If the coil is functioning the idle will drop 25 rpm. If no rpm drop is had the stick coil is bad. If the engine dies, the opposite stick coil is probably bad and the bike is attempting to run on only the lower, conventional coils/plugs.

The idle can be set artificially high masking a bad coil. It might even be possible to mask two failed coils but I’ve never tried it.

The center coil-test should be done for each side. Again a 25 rpm drop per side shows the center coils to be good.

Two photos attached showing example of “good” and “bad” coil part numbers. The manufacture date “/09” and “/11” are the superseded part numbers. The “/03” is original failure-prone” part number.

Again, the original coils fail around 20,000 miles so it doesn’t matter how old the bike is; it’s mileage driven. At 40,000 miles an S could be on its second set of (failed) old coils. My ‘04’s fifth coil failed at 40,000 miles in late 2009. I believe this is the first year of manufacture of the superseded coils. The sixth old coil failed in 2011.

The apparent date-of-manufacture discrepancy (‘09 and ‘11) is due to my moving coils to each new-to-me 1100; one-‘04 1100S and two low mileage, ‘04 BCRs (10,000 and 2,500 miles respectively). The coils hadn’t had time to fail. When I sold each 1100, I told the new owners I had done this and to expect failures. The old coils failed like clockwork.

Once the coils are determined to be good or have been replaced (make sure of the mfg. date if buying used or NOS), then check the idle and TB sync. It was mentioned that a TB throttle plate bushing could be worn allowing unmetered airflow. I don’t think your bike has enough miles to be suffering from this. A cracked, missing or leaking charcoal canister hose from canister to TB could also cause unmetered airflow which causes erratic idling.

The quadrant that rotates the throttle plate when pulled by the throttle cable can be hand-shaken at idle and if it is in-leaking air the idle will change.

DO THE FOLLOWING OUTDOORS AND HAVE A FIRE EXTINGUISHER READY AND KNOW HOW TO USE IT BEFORE TRYING THIS:

Spraying propane at the TB-area, including the charcoal canister hose attachments (or TB-caps if the canister has been removed) will also identify an unmetered air leak. Don’t use starting fluid, brake cleaner or any other liquid mist as the liquid may permanently stain the TBs.

The idle will increase if a suction-leak is present.

[mgp steve]

Looks like only one photo came through will try to load more but the single photo of “old” and “new” coil part numbers should be a help.

[mgp steve]

Looks like only one photo came through will try to load more but the single photo of “old” and “new” coil part numbers should be a help.