Chrysler Repair: Idles too high/fast, spray nozzle, air leaks

Question
I have a 1997 chrysler LHS. I replace the idle controle, idle air controle,oxygen sensor, and MAP sensor. But it still idle around 2000 rpm. Trouble code 12 Says problem with the battery connection. Direct battery input to controller disconnected within the last 50 ignition key-on cycles. Is this something I can fix or do I have too let a service personel handle it?

Answer
Hi Jesse,
Save all the old parts that you replaced because I suspect that most of them are good. The trouble code 12 just means that the battery was either disconnected recently or it has a loose or corroded connection at one of its clamps, but that has nothing to do with fast idle.
The most likely reason for fast idle is that you have an air leak into the intake manifold from one of the vacuum hoses connected to it or one of the sensors or actuators that are bolted to it. When air leaks into the intake manifold it dilutes the mixture which is sensed and compensated for by increasing the gas input, the result is just as if you opened the throttle via the gas pedal, a faster idle.
So what you need to do is look at the sticker on the underside of the hood which shows you all the hoses and items related to the intake manifold. Use the sticker as a road map and look at all those devices and and both ends of all the hoses and check along the length of the hoses for any cracks where air could leak in. You might get a can of spray starter fluid, and put a very tiny spray (if you can change the spray nozzle to one that would allow you to use a straw to better localize the spray) at each joint or object connected to the intake manifold while the engine is idling; and when you do that and the idle goes even higher for just a few seconds you have located such a leak. But don't spray any more than for a fraction of a second and don't spray it on the exhaust manifold because you can start a fire with anything more than a tiny squirt.  It is a very sensitive way to find a leak. But be very careful.
On the battery, remove the - post first and clean it and then the + post. Then put the + post clamp back on. Then finish by putting the - post back on. There is a wire brush and some battery compound in a tube you can buy at the auto parts store to clean the terminals and the clamps. Be careful not to short the + post of the battery to any metal object so as not to be burned.
Roland