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Old 04-17-2008, 10:32 PM
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Join Date: Jul 2002
Location: gray ga
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Talking High idle

79 450Sl when I fist start my 450Sl it will idle about 1800 rpm's - takes about 5 minutes for rpm's to drop to 1000 - help

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Old 04-18-2008, 06:55 AM
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Location: Houston, Texas
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You have a number of small vacuum leaks. Check all of the rubber components on the engine such as; aux air hoses, injector holder O rings, vacuum lines, intake manifold seals - anything that seals air out of the intake system - a long list of things to check.
I got too many cars!! Insurance eats me alive. Dave

78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
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Old 04-18-2008, 09:27 AM
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Originally Posted by jr811 View Post
79 450Sl when I fist start my 450Sl it will idle about 1800 rpm's - takes about 5 minutes for rpm's to drop to 1000 - help


Check the Auxilliary Air Valve. It could be sticking open and that is same as having a vacuum leak. I had same high idle problem, but after cleaning AAV, idle is down to 700 in drive and 800 in neutral.
85 300D14 GLK250,72 350SL, 98 E320
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Old 04-19-2008, 10:55 AM
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Join Date: Dec 2000
Location: Battle Ground, WA
Posts: 576
Unfortunately, that is somewhat the nature of the beast - the '79 has that wax pellet idle air control that is operated by the engine's water temperature, and it takes a few minutes for the water to get hot enough to operate the pellet. Make sure your engine thermostat is in good shape, and that the engine temperature gage shows the engine is warming up. I think the wax pellet starts operating the idle control when the engine temperature reaches 140 degrees.
Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C
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