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1Back to top Go down   Fast idle after fan starts Empty Fast idle after fan starts Tue May 04, 2021 4:08 pm

nino

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Hello, I have a normal idle (1000) until engine reach high temp in city stop and go traffic. Before fan start idle go up between 1500 - 2000. Any advice where to look? When fan out everything look usual. Bike is 1985 K 100. Tnx

    

2Back to top Go down   Fast idle after fan starts Empty Re: Fast idle after fan starts Wed May 05, 2021 5:45 am

92KK 84WW Olaf

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Check the heat from the fan directing very hot air over the back of the radiator and throttle assemblies is not causing the throttle cable to not return properly. Check the clearance between throttle assembly and the clips on the intake rubbers. I had that happen on my K100LT.

That's an easy check before you look for other issues.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 37,190 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 39.885miles.

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

3Back to top Go down   Fast idle after fan starts Empty Re: Fast idle after fan starts Wed May 05, 2021 5:58 am

nino

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Looks like something electric. Is it possible that working fan draw to much current and electric system try to compensate voltage by elevating idle. Everything looks OK except few moments before fan starts when idle rise to 1500 - 2000. When fan start to spin idle sometimes drop to 1000 rpm but sometimes stay high.
Thanks

    

4Back to top Go down   Fast idle after fan starts Empty Re: Fast idle after fan starts Wed May 05, 2021 8:56 am

Laitch

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@nino wrote: Is it possible that working fan draw to much current . . .
If that is happening, be prepared for an electrical fire.


__________________________________________________
1995 K75 81,000 miles
Fast idle after fan starts Usa-lo10
    

5Back to top Go down   Fast idle after fan starts Empty Re: Fast idle after fan starts Wed May 05, 2021 10:37 am

92KK 84WW Olaf

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Run a simple test.....pull the fan relay and see if you get an immediate drop in tick over.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 37,190 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 39.885miles.

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

6Back to top Go down   Fast idle after fan starts Empty Re: Fast idle after fan starts Wed May 05, 2021 7:35 pm

robmack

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The same temperature sensor that is controlling the fan is also sending temperature information to the ECU.  When the temperature reaches 103°C, the fan relay engages and the fan turns on.  The ECU is also sensing the same temperature.  It shouldn't want to raise the idle speed but maybe some other component of the engine is feeding incorrect information to the ECU such that it is causing the injectors to run lean.  It could be the mass airflow sensor, or the Throttle position switch.

Do what Olaf suggests to eliminate the fan circuit.  Then if the idle increases as temperature increases, your problem would be mechanical and you should check the other components I mentioned.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

7Back to top Go down   Fast idle after fan starts Empty Fast idle after fan starts Wed May 05, 2021 8:17 pm

daveyson

daveyson
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Is this a fast idle after the fan starts, or the fan starts after a fast idle? Because it would be normal for the fan to start after a fast idle in city traffic. 

If so, an air leak could cause a fast idle when the engine gets warm, so that would be another place to look.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

8Back to top Go down   Fast idle after fan starts Empty Re: Fast idle after fan starts Fri May 07, 2021 5:07 am

nino

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Could it be aftermarket no name temperature sensor to send rich signal when temperature aproach 100 C? Anybody with experience on non original sensor? Thanks all

    

9Back to top Go down   Fast idle after fan starts Empty Re: Fast idle after fan starts Fri May 07, 2021 6:04 am

92KK 84WW Olaf

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@nino wrote:Could it be aftermarket no name temperature sensor to send rich signal when temperature aproach 100 C? Anybody with experience on non original sensor? Thanks all
Ah, that is likely to be your problem. Did the issue only happen after changing the sensor?


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 37,190 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 39.885miles.

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

10Back to top Go down   Fast idle after fan starts Empty Re: Fast idle after fan starts Sat May 08, 2021 6:24 am

nino

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Olaf, I dont remember if it happen after sensor change two years ago.
But I noticed that battery is weak, 12,01 Volts. One cell was empty. It doesnt receive current on idle, after idle run its impossible to start again. Could it be the cause of erratic idle? (yes Iam stupid)

    

11Back to top Go down   Fast idle after fan starts Empty Re: Fast idle after fan starts Sat May 08, 2021 8:35 am

moriarti

moriarti
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@nino wrote:Could it be aftermarket no name temperature sensor to send rich signal when temperature aproach 100 C? Anybody with experience on non original sensor? Thanks all
Remove IT bin IT fit GENUINE BMW UNIT.Dont fit POOR quality parts, False economy my friend   roundel roundel


__________________________________________________
1984 k100 rs red/black VIN  0004449
    

12Back to top Go down   Fast idle after fan starts Empty Re: Fast idle after fan starts Sat May 08, 2021 9:22 am

Laitch

Laitch
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@nino wrote: One cell was empty. It doesnt receive current on idle, after idle run its impossible to start again. Could it be the cause of erratic idle? 
After you install a new battery—which you should certainly have on your immediate schedule because what you have now is junk—you'll find out.


__________________________________________________
1995 K75 81,000 miles
Fast idle after fan starts Usa-lo10
    

13Back to top Go down   Fast idle after fan starts Empty Re: Fast idle after fan starts Mon May 10, 2021 6:13 am

nino

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Finally it was dirty starter motor with almost dead brushes. It tortured battery (charging) which is 4 years old but still usable. Anyhow I ll change it tommorow. 
Thanks all

    

14Back to top Go down   Fast idle after fan starts Empty Re: Fast idle after fan starts Mon May 10, 2021 9:05 am

Laitch

Laitch
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Thanks for the update. Fast idle after fan starts 112350


__________________________________________________
1995 K75 81,000 miles
Fast idle after fan starts Usa-lo10
    

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