Originally Posted by
Ricker
Therefore, I believe I need a new idle speed motor. Am I missing anything before I buy a new idle speed motor?
Sounds like your ISM is OK. It's clean inside and it hums when it should. I'd check for leaks first - see below - but will mention more ISM stuff first.
One more elec verif test for it: Unplug the connector from the top of the ISM. You can see the 3 male connectors on it. Check the DC resistance from the center male spade to each of the outer spades. It should be something like 10-20 Ohms to each outer one but don't quote me.
If you still suspect the ISM see if you can find a D owner nearby who'll lend you a known good one from their car or from their spares pile for a day or two.
Look for air leaking into your intake system. The usual culprits are already mentioned. Decel springs, throttle linkage, loose/cracked hoses or vacuum lines. Also check the injector seals, the distributor advance solenoid and the upper body of the ISM (its seal can crack near the connector). There are threads in this forum about the springs.
To find vac leaks have a mechanic run a smoke test for you if you don't have access to a good smoke machine. It takes less than half an hour.