Chrysler Repair: Hesitation when ac is on., shadetree mechanic, haynes manual

Question
Recently I had hesitation on my 1999 Voyager. I have 114,000 miles.  When I replaced the spark plugs I noticed a huge improvement but I still have hesitation, jerking when I use the ac.  When the ac is not running the van does not hesitate. I recently listened to the engine when It was parked in the driveway with the air on and it seemed like it clicked and then the engine changed speeds. I believe its an ac problem. Any help would be appreciated. Thanks
Mark

Answer
Hi Mark,
The engine controller is involved with the A/C in actually initiating the compressor clutch to activate the compressor when you turn it on at the control panel. It is programmed to increase the idle speed as well to take into account the drag of powering the compressor. The click you heard may by the clutch releasing and the subsequent decline in the idle speed, and the reverse when the A/C clutch is set again. The A/C cycles because the pressure in the refrigerant system rises and falls with usage and must be maintained in a fairly narrow range and this is done by cycling the compressor. All that said, it doesn't explain the hesitation, except to recongize that some of the engine output is being taken up by the compressor when you have the A/C activated. It could be that the compression has decreased on one or more cylinders so there is just less power output. A test with a tester would tell you the answer.
The Haynes manual lists these possibilities for hesitation (stumbling) on acceleration: spark plugs fouled, fuel filter clogged, malfunctioning fuel supply or injector system, malfunctioning engine control system, EVAP system leak or malfunction, alternator output low or excessive. So you might want to review those against your maintenance records and check those items that are straightforward for the shadetree mechanic.
Roland