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Discussion Starter #1
Hello from Georgia!

I have an '03 LT that I bought last summer. A few weeks ago, the throttle cable broke when I was on my way to the dealer for a new rear tire. I had roadside assistance with my insurance company and had the bike put on a flat bed and taken to the dealer. So, instead of just looking at a new tire, I was looking at a new style throttle cable and retro-fit kit. While the tank and tupperware was off the bike, I had them go ahead and and perform the 36K service and replace the heated grips that were split in numerous places.

OK, I should be ready to roll, Right???...Wrong, the tech returns from a test ride and indicates that the bike is losing power and top end "ummph" at around the 4500 rpm range. They diagnose it as a bad throttle potentiometer.

Keep in mind that I didn't notice any lack of power before the trottle cable snapped. I didn't ride the bike myself after the diagosis, but I have them go ahead and replace throttle potentiometer.

I get the bike back last Friday and I immediately stall it in the parking lot. I assumed I might just need to get used to the new throttle potentiometer or I was just nervous after dropping so much money in one visit. I continued on a lengthy ride (200 miles) and stall it three more times. the bike hesitates from a standing stop and it feels as if I'm starting off in 2nd gear. It's also missing like there is a mixture problem and my gas mileage dropped from an average of 46 to an average of 31.

I take it back to the dealer and they've had it for a week trying to diagnose the problem. So far they say motronics unit or oxygen sensor but BMW diagnostics can say for sure which one is the problem.

Does anyone have any ideas? The brown wire is still intact.

Keep in mind the bike was running fine before the throttle cable snapped...

I'm getting discouraged. :confused: :confused: :confused:
 

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rough guess I'de say vacumn leak at the throttle bodies from the cable change or something like that, the brown wire from what I read is only applicable to really hot climate conditions. because it is at the dealer you are at their mercy. if I was doing it at home I would be stripping off the plastic and rechecking for a vacumn leak
 

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At this point I would be questioning the dealer's service quality. The bike needed a throtle cable and suddenly all of these other issues?? I also believe it is vacum related and or an electrical connection has been missed or misaligned. If the fuel filter was replaced, were the lines at the filter reversed, but then you were able to ride the bike home so the problem would have been from the start. Can the dealer explain how all of these problems have surfaced only after he began to tinker with it?
 

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I agree on the vacuum leak.
check the small vacuum hoses on left engine side.

when replacing the throttle cables, you can easily pull one off if your not careful.
 

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When sitting still and idling (after warm up) does the idle speed "hunt" up and down ~500 rpm? If yes, that's a sign of a vacuum leak (the Motronic is reading excess air in the exhaust, adds more fuel, which causes idle to go up, then the Moronic removes fuel/adjusts the idle speed actuator to lower idle speed, then the oxygen sensor sees too much oxygen in the exhaust, and ...).

The fact that it's right after a service is a clue -- it is not unheard of for one of the four small vapor recovery hoses to get knocked off its throttle body nipple. More specifically, with the potentiometer replacement, I'd lay odds on #4 being off, as it's right next to the potentiometer and it's a bit hidden -- easy to overlook when throwing the tupperware back on.
 

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Discussion Starter #6
mneblett said:
When sitting still and idling (after warm up) does the idle speed "hunt" up and down ~500 rpm? If yes, that's a sign of a vacuum leak (the Motronic is reading excess air in the exhaust, adds more fuel, which causes idle to go up, then the Moronic removes fuel/adjusts the idle speed actuator to lower idle speed, then the oxygen sensor sees too much oxygen in the exhaust, and ...).

The fact that it's right after a service is a clue -- it is not unheard of for one of the four small vapor recovery hoses to get knocked off its throttle body nipple. More specifically, with the potentiometer replacement, I'd lay odds on #4 being off, as it's right next to the potentiometer and it's a bit hidden -- easy to overlook when throwing the tupperware back on.
Didn't notice the idle speed jumping around when I test rode the bike today. They just changed the O2 sensor and there is no difference...Still runs like crap. Although the Motronic is testing "good", they (the dealer mechanics) still suspect it could be the problem. A call has been made to the BMW Field Service Tech who lives in the Atlanta area. I hope he can take a look early next week. In the meantime, I'm really getting frustrated.
 

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Throttle body or plenum...........one or the other...................vacuum leak........try the starting fluid test..........if you spray it lightlly along the length of the plenum and lines, a leak will show up as an increase in the idle speed.................'nuff said ........... :)
 

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Palerider said:
Throttle body or plenum...........one or the other...................vacuum leak........try the starting fluid test..........if you spray it lightlly along the length of the plenum and lines, a leak will show up as an increase in the idle speed.................'nuff said ........... :)
DO NOT USE STARTING FLUID !!!!!!!
 

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Vacuum leak:

There is rubber above the throttle bodies #6
There is rubber below the throttle bodies #3
There is a rubber hose from the crankcase to the throttle bodies $5
There is a rubber house in the area #14

Now have a good day and go find your leak . . . :D

 

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