E21 idle speed

I just put an engine in my 1978 320i. I got the engine from a wrecked 78 with 85000 on it and the engine was running pretty well, but now that I took it out and put it in the other car, it idles at about 2500 rpm. It starts right up, idles for a few seconds and then the idle speed increases quickly to about 2500. I can't find any vacuum lines that appear wrong. What could cause this and how can I fix it?

If it has fuel injection the bypass valve that opens when the engine is cold is probably stuck. And it also has some hoses that can become loose sometimes. So that might be your problem. The valve is like a disc shape thing between the valve cover and the plenum which and electric connection. Otherwise something is wrong with the fuel distributor or spme crapy ass warm up regulator and stuff.

If thats a carb. Check the choke and electric connection, your idle mixture, and I beleive there is some sort of warm up circut too in it. Its just a simple carb problem-rebuild the piece of crap or get a good working from a wrecker.

Wats up with such a low mlg? Whats the comression on it? 85000 thats nice