Adjusting idle mixture bypassing computer

I am seeing several cars from the early 90's that are idling rich and we can't figure out what the problem is. After checking the simple things - plugs, vacuum hoses and connections, next idea was the computer was not getting the right signal from the mass air flow sensor. Swapping that out didn't improve anything.
All we really need to do is manually adjust the idle mixture, but as far as I can tell this is not possible due to all the controls coming from the computer.
Anyone run across this before and have an idea what to look at next? Or how to bypass the computer and adjust the idle mixture
Thanks in advance.
Bob
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Guv Bob wrote:

bad temp sensors - could be 3 of them bad IAC, MAT, MAP, MAF bad O2 sensors - could be 4 of them bad injectors air leak between intake and MAF blown pressure regulator
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On 2/10/2012 11:45 AM, Guv Bob wrote:

I'd suspect the IAC myself...
--
I'm never going to grow up.

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Thanks, Peter. Looks like I'll need to price out some parts and start swapping the out. I'm not that up on emissions systems. Found this... http://www.autoshop101.com/forms/h60.pdf
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