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  #1  
Old 11-24-2014, 07:34 AM
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Strange Idle Problem

The idle on my 81 380sl drops and then immediately rises every 15 seconds or so when the the car is in P or N when the heater is off. However, if I turn the heater on or put the car in gear the idle stays steady.

I replaced the idle control unit with a rebuilt one twice now and the idle control valve seems to be fine. So, I'm assuming it has something to do with the fact that the AC compressor comes on when the heater does, and the effect this has on the vacuum advance and/or changeover valve. But I'm not sure how to correct the problem or even diagnose it. So, I was hoping someone here could tell me what to look for.

Thanks very much in advance.

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1981 380SL
Chassis: R107.045
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  #2  
Old 11-25-2014, 11:01 AM
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search auxillary air valve, or AAV that will get you started . I beleive yours is electronic so not sure it is adjustible
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2011 Porsche Cayman - Bond,James Bond
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  #3  
Old 11-26-2014, 06:31 AM
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Quote:
Originally Posted by meltedpanda View Post
search auxillary air valve, or AAV that will get you started . I beleive yours is electronic so not sure it is adjustible
i cleaned that valve not too long ago, but it didn't help. Plus, if it were the valve, you'd think that it would cause the idle to oscillate the same way when the heater and compressor were on or off. Wouldn't you?
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1981 380SL
Chassis: R107.045
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  #4  
Old 11-26-2014, 08:13 PM
meltedpanda's Avatar
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you would think so , but AC compessor on requires more HP and increase in idle , so it is possible , the heater piece is the mystery

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Ron
2011 Porsche Cayman - Bond,James Bond
Sadly MERCEDESLESS - ALways LOOKING !
99 E320 THE Queen Mary - SOLD
62 220b - Dolly - Finally my Finny! Sadly SOLD
72 450SL, Pearl-SOLD
16 F350 6.7 Diesel -THOR
19 BMW X5 - Heaven on Wheels
14 38HP John Deere 3038E Tractor -Mean Green
84 300SD, Benjamin -SOLD
71 220 - W115-Libby ( my first love) -SOLD
73 280 - W114 "Organspende" Rest in Peace
81 380 SL - Rest in Peace
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