Chrysler Repair: Possible electrical problem with Chrysler Saratoga., chrysler saratoga, ais motor

Question
Hi.. I have strange problem with Chrysler Saratoga -92, with the 3.0 v6 engine. This problem arised first some time ago, when there was some basic maintenance being done to the car. The symptoms were irratic idle and noticable change in the power of the engine. Since we suspected an electrical problem, we replaced the map-sensor, and the coolant temp. sensor. This didn't seem to help, and as i checked, there was no error codes, when made the key-turn test. However, somehow this problem went away when we were fiddling with the power cables of the car. Suddenly the power was back, and also the idle was normal, around 600rpm pretty constant. After this, the car was driven normally for a while and it was working the whole time. Well, the problem came again now, with exactly the same symptoms, again after a maintenance being done to the car, drivebelt replacement, to be exact. We went and replaced the oxygen sensor, since we still suspected an electrical problem considering the same symptoms. However, this didn't help. I have checked the codes are given from the computer, except the 55 which should be end of codes. So, these things being done.. Do you have any suggestions for testing something or so? I thought of tps as one thing to test, but im not sure, if it has effect on the fuel mixture on idle? Since my assumption is, that the mixture isn't right considering the symptoms. And i forgot to mention that the ais-motor was also cleaned when the problem first appeared. I have a voltage-meter handy incase i could test something.. So i would appreciate any help you might have for me here.. Thank you in advance for your reply.. :)

Answer
Hi Ville,
I am always interested in the historic concidences of various changes with function of the engine. Your suspicion of an electrical intermittancy is worth pursuing by shaking the various harnesses with the engine idling to see if you can effect a change. Also you might rethink the steps in the recent maintenance as to whether any of them would have tampered with cables or mechanical functions.
The throttle position sensor is a factor, one of many, in the control of the engine even at idle. It should have a voltage output of less than 1 volt with the throttle fully closed (orange/dark blue wire), and the voltage should rise smoothly as you open the throttle.
Unfortunately there so many other possibilities for erratic idle and loss of power that I am reluctant to just give you a long list which is going to be difficult to accomplish.
An irratic idle can be caused by a vacuum leak, so it is worth while to check all the vacuum hoses using the underhood sticker as a road map. Another possibility is that the egr valve is not closing tightly when at idle due to a build up of crud inside the valve. That valve is supposed to be taightly closed at idle and at full throttle.  Also check the vacuum hose and electrical connection and wires to the solenoid that is associated with the valve. The air filter being clogged is a possibility but tht wouldn't usually be an on-again off-again sort of thing so I wouldn't expect that to be your problem. The fuel pressure might be worth verifying: 47 psi. And as always it would be worth inspecting the timing belt for wear/breaking down if it is getting high in its mileage of use. Spark quality might be assessed to see if the coil is weak: (back away the tip of the distributor's detached center wire (beginning from an initial 1/4" gap from a engine ground surface, while cranking the engine) to see if the spark quality is good and if any arcing occurs at the coil tower as you increase the spark gap.  
There are many other possiblities but these are the most likely ones.
I have a feeling that your skills are such that this is one you will figure out. Let me know when you do!
Roland
P.S. What body style is the Saratoga (a Van?).