450slc replaced cold start valve - still a problem

Hello, Yesterday I had a problem that sounded like it could only be the cold start valve. So, I replaced it today. Now I seem to have a different problem in the same area. My timing is a little high at 45 @
3000rpm with full vacuum, so I'm going to drop it a hair, shooting for 42. After replacing the cold start valve, I still had a high idle (about 2,000rpm). I started to adjust the idle down and I was just 1/2 turn from all the way in. So, I started backing it out. As soon as I did that, it started surging... 1 sec at 2,000rpm, 1 sec at 500rpm... on and on.
Any ideas on what might cause this? Thanks in advance, Tim
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Did you replace the cold start valve or the slide valve ?, I thought I read yesterday that you have a 1974, if you do you need to replace the slide valve, or/and look for other vacuum leaks. Martin. Autobahn Auto

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Martin, Thanks for the advise but I'm lost now. I don't know what the slide valve is. Can you describe it and tell me where to look for it? I've looked everywhere for vacuum leaks and can't find any but I'll keep looking and check evey hose on the car. Thanks, Tim
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OK, The valve is mounted on the very center fron of the intake manifold, even with the air filter on the engine you see a 2 inch tall cylinder looking piece that is connected to with 2 hoses (1inch diameter) to the manifold, the 2 hoses are on the opposite from each other the way they enter the slide valve. The valve itself is mounted with size 10mm wrench screws, speaking of wrench, Bill ditmire (wrench99) mentioned to tab on the valve while the engine is operating temperature and see if the idle goes down (he didn't say all that, but I just did). He didn't call it a slide valve but he responded to your cold start valve that way and I know he meant the same thing I did. A cold start valve wouldn't make your engine idle high. Keep us posted, copy to my e-mail so I don't have to come here everytime :-). Martin. Autobahn Auto
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I'll be interested in knowing what the final solution is. My car (73 SLC) has a similar problem, but not nearly as severe as yours.
Steve

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Hey guys, Thanks to wrench99a and bnzmn600. You were both right about my problem. I misunderstood in the first post from wrench99. I saw the description but when I told my parts guy I wanted a "cold start valve", his book and computer showed what I would have called a "cold start injector". So when I replaced it, it didn't quite do the job. Today I replaced what my parts guy called an Air slide valve and it worked like a champ. The car runs like a dream. now all I have to do is blow out the carbon from running (in the past) with burnt points and timing about 30 deg off. Thanks a bunch guys, you sure know your stuff! Tim Dodson - Roswell, GA
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