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Discussion Starter #1
I have a '79 450sl with 210K on the engine. The problem I'm having is that the car has a miss at idle. The number 5 cylinder is the culprit. Compression is still great on all the cylinders including #5. I have replaced the plugs, wires, distributor cap and rotor, and even the injector for #5.

I also notice that the car seems to run lean, as the plugs do not even get brown. I suspect a vacuum leak, but am having a hard time isolating it. I doused the engine with both carb cleaner, looking for a spot that would cause the idle to change and pinpoint a leak, but so far nothing. When I put my hand over the throttle plate and try to "choke" the engine, it takes a long time to die out, thus making me wonder if something is cracked or broken under the intake manifold...

Any ideas??
 

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the boot/various seals under there are prone to cracking.. Have you taken a vacuum reading off the back of the intake manifold?

Jonathan
 

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Discussion Starter #3
I will certainly give that a try. I've just ordered all the rubber seals and hoses for the upper and lower intake, as I've found the intake hoses to as fragile as glass.
 
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