Still Misfiring: Suggestions Please? - BMW Luxury Touring Community
 
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Old Sep 15th, 2013, 7:28 pm Thread Starter
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Still Misfiring: Suggestions Please?

The patient is a 1999 K1200LT that has developed an annoying misfire and erratic (even clattering) acceleration; BUT ONLY WHEN IT"S WARMED UP. When started cold it idles and runs perfectly to any speed at any rate of acceleration until the temperature gets to about normal and then it starts to run like hell. So far I have: replaced plugs and wires, adjusted valves, changed fuel filter and all internal tank hoses (found to be OK), and checked all vacuum lines for leaks. I've also unplugged the air box sensor. I've run various injector cleaners through the last three tanks of fuel There is one plug that seems to run very slightly sooty but it's done that since I acquired the beast about 10K miles ago. It hasn't changed. The problem developed suddenly on two-up ride, occurring only occasionally but then increasing in frequency over a few hundred miles until it's a sure bet now. When it gets hot it starts to miss, surge, and buck.

All theories welcome!

Best, Bumboo in Portsmouth, VA
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Old Sep 15th, 2013, 8:24 pm
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Re: Still Misfiring: Suggestions Please?

possibly the temp sensor in the head, tranny end of head

Gary
2018 R1200RT
Past rides
2012 K1600GTL
2000 K1200LT
1992 K1100LT
2000 V Star 650/Velorex sidecar
1985 K100RT
1965 R60/2
1960 AJS 500 single
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Old Sep 15th, 2013, 8:46 pm
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Re: Still Misfiring: Suggestions Please?

If it accelerates normally under full throttle, check the O2 sensor. If it runs poorly at full throttle, then you may have an issue with your pick-up coil, engine temperature sensor, coolant temperature sensor, etc. Since you have unplugged the intake air temperature sensor, I'm leaning towards the O2 sensor. But before you get too excited, make sure it's producing 50 PSI on the fuel rail.


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Old Sep 15th, 2013, 9:52 pm Thread Starter
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Re: Still Misfiring: Suggestions Please?

Thanks a million. I'm leaning towards the O2 Sensor. The bike has 42K miles and I'm sure it's original and I see other forum members have had O2 issues with similar symptoms. From reading the forum I also find my mileage is terrible compared to that reported by others. It's consistently delivered only about 34 mpg since I got it. So regardless of whether a new O2 sensor relieves my problem, it looks like a new one is warranted. I'll pick one up, install it and report back. I do have 50 psi at the fuel rail. The misfire and surging under hard acceleration is not nearly so chronic as when just taking off easy.
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Old Sep 15th, 2013, 10:20 pm
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Re: Still Misfiring: Suggestions Please?

Maybe worth doing a check on the ignition Hall Effect Sensor (HES). K100 engines used to suffer a bit from erratic running when up to temperature and somitimes the HES was the culprit. To conduct a test, remove the cover on the front RH side of the engine (crankshaft side of cam chain cover) and use a hair dryer to blow hot air in there when the engine is cold. It may cause the rough running you describe, though it may be that engine load is required to manifest the condition. HTH.

Dennis
1987 Yamaha TY250R
1991 Aprilia Climber 280
1988 K100RT (the pack horse)
2005 K1200LTE Light yellow metallic
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Old Sep 18th, 2013, 8:53 pm Thread Starter
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Re: Still Misfiring: Suggestions Please? Update.

Problem Review: The 99 LT with 38K miles runs perfectly until it warms up and then it runs like crap and is not driveable. Top speed drops to <90mph. If you romp on it while the temp is still in "cold zone" it will make a ton like a rocket-smooth as silk. Based upon your suggestions I have done the following in addition to the aforementioned work noted in this post: Changed O2 sensor; changed fuel pump (was just slightly low on output pressure); heated the Hall effect sensor with a heat gun to simulate a quick warm up and it had no affect; and checked the spark plugs which are all light brown with the exception of #1 which is just barely sooty. Once warm, the bike also makes a gawdawful........ clank bang bank-bank clack noise from the left side of the engine that sounds like it's more to the rear when listened to with a stethoscope. When cold that noise is not there??? The missing on acceleration is also accompanied with a almost quick violent surge with a noticeable pop or bang that feels almost like a gear jumping a tooth. I'll need to check compression which was stock when I got the bike about 10K miles ago but it don't have a gauge to fit the tiny plug hole. I'm beginning to suspect something catastrophic has let go inside. I've owned, serviced and even rebuilt over 20 BMWs: /2s /5/s, /6s,/7s, flying bricks, and oil heads but this one has me beaten. I'm sure I "can" eventually figure it out but Beemers should be about riding, not fixing. Please, any more suggestions before I consider scrapping it. Thanks again.
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Old Sep 18th, 2013, 9:44 pm
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Re: Still Misfiring: Suggestions Please?

In another thread, the owner found his issues to be an aftermarket power chip. Anything like that in your bike?


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Old Sep 18th, 2013, 11:02 pm
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Re: Still Misfiring: Suggestions Please?

You might try checking the oil pressure. low oil pressure when warm could cause inadequate tensioner pressure and a loose timing chain and erratic timing. Just throwing it out there because it sounds like you've checked everything else you can.

A quick and dirty way to check is to add STP or Gear lube to your oil, and raise the viscosity. If it improves things, you have a clue. If it doesn't, you do an oil change.

The only other thing that comes to mind is the ECU or a sensor that affects the hot running map. Temp sensor, O2 sensor etc.

Is something like the Air Box Temp sensor disconnected and the brown wire cut at the same time a possible problem on your bike? Yours is a 99 so you don't have a brown wire but someone may have 'upgraded' it to a later ECU and it may think the wire is cut....

Best of luck and here's hoping you figure it out.

53 MPG and life just keeps getting better

2001 Triumph Sprint ST [sold]
2000 K1200LT 'Nimitz'

Last edited by Centaurious; Sep 18th, 2013 at 11:09 pm.
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Old Sep 19th, 2013, 6:18 am Thread Starter
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Re: Still Misfiring: Suggestions Please?

Thanks for the suggestions. The help is most appreciated and I am greatly thankful ot have a great forum like this to wail to. The ECU is orginal OEM and it's clearly suspect but short of replacing it at great expense I'm not sure there's much way to check it. Guess I'll need to consider that. The 02 sensor is new. The air box sensor is disconnected (no brown wire), and I've run the bike with another known good temp sensor from 2000 LT. I considered oil pressure as a possibility so I changed the oil and added fresh w/ a quart of Lucas Oil Treatment in lieu of regular oil. I have the service records from the PO who was diligent in changing fluids but did little else, including riding it; so the bike went unused for most of it's first 12 years. However, it ran perfectly when I acquired it and this problem developed on a trip and progressively got worse. Last evening I inspected the cylinder walls and piston crowns with a borescope. All normal except for a light oily coating on the top of the rearmost piston. I did note that that on the last run with new plugs that it looks like it's running quite lean with all plugs but one one snowy white after about 100 miles of running and testing. Maybe a clue? I don't have a scanner and can't locate one to borrow locally. Our nearest dealer with a brain is 120 miles away. Is there any value in trailing it up there for a scan? Best, Mike in Portsmouthk, VA
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Old Sep 19th, 2013, 7:51 am
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Re: Still Misfiring: Suggestions Please?

there has been at least 1 failure of the rubber absorber in the output shaft, bottom of engine, drives clutch - if it feels like a mechanical issue, "jumping teeth" in tranny - just throwing it out e

Gary
2018 R1200RT
Past rides
2012 K1600GTL
2000 K1200LT
1992 K1100LT
2000 V Star 650/Velorex sidecar
1985 K100RT
1965 R60/2
1960 AJS 500 single
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Old Sep 19th, 2013, 8:38 am Thread Starter
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Re: Still Misfiring: Suggestions Please?

Hmmm....rubber absorber on the output shaft. Yes, most times when it misses and surges (again only when warmed up) it feels just jumping a tooth in a tranny. My thought was that some sort of ignition misfire was exacerbating the backlash in the clutch and gear train and causing the "jumping-banging" effect. After working the engine over again w/ stethoscope last p.m. I revised my estimate of the noise origin. It now seems to be centered on the lower right side of the engine about where the absorber is located. A possibility for sure or just another problem not related to the misfire but amplified when it misses or fires off sync. The odd thing here is that prior to reaching normal temp, the noise is not there, nor the misfire. I hear maybe some "clicking" in the same location but does it ever get louder once the crankcase and oil are hot! I'm going to stay with it for a little longer and see if I can resolve it. These things aren't foreign to me; I own a business that repairs diesels from one to 2000 HP and fixes some precision high-tech stuff; mechanical, electrical, and electronic. But rather than spend another 40+ hours or so sorting it out I may just cut my losses and let 'er go for parts and spend the time riding. On this BMW w/ 38K miles I've spent about as much time servicing and sustaining it ( and fixing other friends LT's) than I've ridden it. With my wife aboard it's the finest motorcycle I've ever ridden but I don't think it's BMW's high point for reliability. Maybe back to a R100 that I can overhaul with a Leatherman. Thanks for the suggestion! I'll stay in touch with all you kind folk as I ponder what to do next.
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Old Sep 19th, 2013, 9:10 am
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Cool Re: Still Misfiring: Suggestions Please?

Quote:
Originally Posted by gary45
there has been at least 1 failure of the rubber absorber in the output shaft, bottom of engine, drives clutch - if it feels like a mechanical issue, "jumping teeth" in tranny - just throwing it out e
Here is a thread with some pictures of a failed Drive Shaft. There have been a few failures where the rubber de-bonded and caused slippage.
http://www.bmwlt.com/forums/showthre...+shaft+failure

Good Luck!

John

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'00 K1200LTC "Katie"
'95 Triumph "Tigger"
'12 Triumph 800XC "Tigger II" (RIP)
'12 Triumph 1200 Explorer "Shadow Tigger"
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Old Sep 19th, 2013, 11:14 am Thread Starter
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Re: Still Misfiring: Suggestions Please?

Could be you're on to something here with the rubber bonding on the driveshaft. It will few days before I can check it. It doesn't explain the clanking noise at idle after warm up but it would account for the "missing tooth" feeling. What I've taken as a misfire fire could be intermittent and irregular slipping of the drive shaft. In fact, if I settle the bike down to a steady speed the problem all but goes away but recurs right away on acceleration. Still I'd wonder why the drive shaft would be temperature related; maybe coincidental. The problem will start almost precisely when the temp gauge needle touches the mid point line on the analog gauge. In fact, I ride the same test route each time I try something new as a fix and the problem will inevitably start within a block or two of the same stretch of road. Thanks for the pics and the suggestion. MAM in Portsmouth, VA
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Old Sep 19th, 2013, 7:41 pm
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Re: Still Misfiring: Suggestions Please?

This is the damper they were referring to on the output shaft. I saw one where all the vanes where sheared off and the rubber was gone (where did the rubber go...?)
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John
2009 K1300GT Red Rocket
2009 R1200GS (Gone)
2005 K1200LT Ocean Blue Blue Wizard 110 K and counting...
2006 Bushtec Turbo+2 Spell
2004 330 Ci Convertable
K4AN

Have ridden a Motorcycle in all 48
But lack DE, MA, RI and CT with the 2005 LT

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Old Sep 20th, 2013, 2:46 pm
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Re: Still Misfiring: Suggestions Please?

This is what a bad drive shaft looks like. The rubber should be well inside the outlines of the shaft and smooth.
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John
2009 K1300GT Red Rocket
2009 R1200GS (Gone)
2005 K1200LT Ocean Blue Blue Wizard 110 K and counting...
2006 Bushtec Turbo+2 Spell
2004 330 Ci Convertable
K4AN

Have ridden a Motorcycle in all 48
But lack DE, MA, RI and CT with the 2005 LT

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