Your Symptoms Sound Very Similar to My Symptoms?:
POs experienced very infrequent symptoms of feeling like running on less than 6 cyls......I experienced very infrequent idle problems over a 6 month period after I acquired the vehicle.....mostly highway miles so it happened about every 100th traffic light when stopped ..... then as I tried to shake the bugs out the frequncy increased....always thought it was cheap or low octane fuel.......finally stalled a few times and no started a few times .....ignition switch finally went, but i could start her remotely (wired trigger remote).
I shook so much of the wiring around when I was trouble shooting the no start due to the ignition switch that I increased the frequency. So now she would start with the new switch but ran like crap.....most of the time....however sometimes she would run good.....tried everything.....fuel filter, both fuel pumps, fuel pressure regulator, voltage regulator, coil, cap, rotor, plugs, throttle control switch, computers, ICM module, relays, alternator, ground cable, afm rebuild .....all to no avail.....in fact the more i did the worse it ran.....intitially I had checked the CTS (coolant temperature sensor) everything checked out okay. Resistance values corresponded to specs at various temperatures. However, i discovered that there was an intermittnet open circuit in the CTS circuit at the connector from the wireharness to the CTS right on top of the engine and right in front of my face all the time. If it were a poisonous snake i'd be dead right now.
The wiring looked okay intially even the open shrink sleaving with the resistor soldered into the circuit about 2 inches back from the connector. solder joints looked good as did the wiring.....resistor according to my research had been installed on 84 - 633 CSIs post production I believe at dealers to correct a lean condition. I noticed that resistor was further up the wire harness and in the shrink sleeving not in the boot on the connector as described in the research. I always kept going back to this point....as it looked suspicious all along but now my curiosity and desperation kicked in the survival skills so I took my razor blade out and carefully slit the rubber boot that covered the connector wire harness transition and as I gingerly removed the boot, behold an even smaller resistor appeared and the wiring, solder joints, resistor, and resistor leads practically dissentigrated in my hands as the 20 years of corrosion within the confines of the boot(not completely moisture proof by the way)caught up with her.
The resultant intermittent open circuit caused the problems all along. Any open circuit or partially open circuit in the CTS loop of the ECU feedback system is going to cause these type of problems .....so check the wiring, connections, etc. very carefully.....I would recommend using a continuity meter and checking the entire lenght of the harness while simulating vibration conditions by shaking the wire harness around. I think this circuit is the culprit to many of the problems experienced on this board as the symptoms are always the same and the attempted solutions always seem to be unfruitful or only temporary ....just shutting the hood on this vehicle is enough to jostle this circuit into performing correctly or incorrectly....amazing but true if you have a loose wire or slightly corroded connection .... Check it out to be sure!