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Discussion Starter #1
i have always had a fast idle on my 2000 LT , about 1500 RPM.
I am going to try one more time very carefully with the manual to adjust.
If not is there a typical place to look for a vacuum leak?
 

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i have always had a fast idle on my 2000 LT , about 1500 RPM.
I am going to try one more time very carefully with the manual to adjust.
If not is there a typical place to look for a vacuum leak?
No supported / described way to manually adjust idle. It is done by the stepper motor. Perhaps the GS911 / TPS-test might give an indication if the stepper is out of it's limits.

As for the vacuum leak I am not aware of typical place for leak. Would test with spraying start gas around the throttle bodies
 

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Most common vacuum leak is in the vacuum lines to the throttle bodies that go to the solenoid valve and then to the charcoal canister. Solenoid valve could be stuck open, try plugging the outlet line on it to the canister.

There can be vacuum leaks in the throttle body seals where they attach to the head, but that is not all that common.

I would try removing the four vacuum lines to the throttle bodies and plugging the throttle body nipples (you can get vacuum caps at auto parts stores, but easy to just put tape over them) and try running the engine then.

If not a vacuum leak, you could have a bad throttle positioner, but that again is a very rare problem, more likely to have a problem with the Engine Control Module.
 

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Discussion Starter #4
Thanks David
 

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Mine had a high idle after I puled the TBs off to do some service work. Turns out I had bent the bracket holding the idle air controller. This kept the idle controller from shutting the TBs far enough because it (idle motor) has an upper and lower limit when it operates. It in turn must be within appropriate limits to operate properly. Your engine basically responds to either the amount of incoming air (which is why a vacuum leak causes high idle) and/or the input from the throttle position switch/sensor. Study the adjustment screw/nut which interfaces with the idle motor and you'll figure it out.
 

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Discussion Starter #6
Thanks Dean
 

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Discussion Starter #7
I am thinking of replacing the cables
a; because the bike is 14 years old
b: bmw says replace at 30 thou or so, I have 109 thou KM
c: I do not like the risk of a broken cable.

Having said all that I am just wondering if the PO had changed cables and in the process bent a bracket to cause the fast idle.

Is this a reasonable possibility?
 

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I am thinking of replacing the cables
a; because the bike is 14 years old
b: bmw says replace at 30 thou or so, I have 109 thou KM
c: I do not like the risk of a broken cable.

Having said all that I am just wondering if the PO had changed cables and in the process bent a bracket to cause the fast idle.

Is this a reasonable possibility?
Your guess is as good as our's :) Why couldn't something like that happen. Nothing is safe from eager "home technician". On the other hand if that is the case it should be visible by GS911 (if one available) like any other possible "home-made-did-not-know-what-was-doing-efforts" to adjust idle. ;)
 

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I am thinking of replacing the cables
a; because the bike is 14 years old
b: bmw says replace at 30 thou or so, I have 109 thou KM
c: I do not like the risk of a broken cable.

Having said all that I am just wondering if the PO had changed cables and in the process bent a bracket to cause the fast idle.

Is this a reasonable possibility?
I have done a lot of work and testing related to the Throttle-bodies adjustments - including checking errors with GS911. I have also swapped TB-assy and opened them for cleaning and inspection.

In my opinion, if nothing as ever been opened or removed (TB-assy or cables) most high idle condition come with age caused by intake air-leaks after 5 to 10 years. Often related to small vacuum hoses, rubber intake tube between cylinder-head and TB-assy, or O-ring under intake manifolds.

BUT... in real-life, most often something has been opened or removed for maintenance. In such case, much before the age of rubber components makes it as problem, I find the throttle-cable(s) free-play to be the main issue causing problems. If the throttle does not snap back completely closed (with some free-play at handle-bar), the Motronic-ECU gets confused because it sees a higher TPS at rest when ignition is turned ON.

So in order of easy to more complex:
(1) make sure you have free play as documented in shop-manual (or Clymer)
(2) make sure the throttle-close is positive and consistent. If cables feel stiiff and do not come back normally, better to replace in garage than on the road ;-)
(3) inspect small vacuum hoses (maybe loose , or a leak). As suggested before, just plug all of them or the nippples on TB-assy to eliminate these as potential cause.
(4) if you have acces to GS911, have a check for TPS base setting (this requires to remove TVA - also called idle actuator)

I will not explain the TVA (idle-actuator) check as it would take a fairly long post with picture. Easier to start with the "most probable" list above.

Last, but the least of a job, you may need to replace TB-assy related rubber parts described above, if you cannot find a solution with the easier stuff listed. If you have to go there to install 2 new throttle-cables (pull cable and return-cable) , you might as well do the rubber parts at same time. Once all that is done, you are good for another 8 to 10 years unless you do 25,000 miles each year ;-)
 

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Discussion Starter #10
Thank you for an excellent reply.
 
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