2002 Bonneville RPM/Voltage fluctuates while idling
Hi, Im new to the forum but have been searching it most of the past 2 weeks. I recently purchased a 2002 Bonneville SE for my sister in Arizona and drove it back to Ohio 2 weeks ago. When I was leaving AZ the car stalled at the first red light I hit, then drove strong for 2000 miles over 2 days with no problems. Since I delivered it to her it has stalled a few times, always while stopped or stopping. When starting the car, it idles roughly. I see the RPM fluctuate between 700-900, and when the RPM dips I notice the Voltage dipping below 14 and the lights dim. Once you start driving it it doesn't have any problems, I drove it for 14 hours straight during my trip with only 2 breaks. She has had similar results, while on the highway or driving at a decent rate the car runs great.
After searching and scouring these forums I see the camshaft position sensor as a possible culprit but all the posts I have read mention their cars stalling while driving, while this one seems to only stall when stopping or stopped. I have read that the PCM controls idling under 1200 RPM and the CPS is integral in this, any way to test this out? Is the CPS still located below the water pump on an 2002, all the times Ive seen it mentioned it was on older models. Perhaps the MAP sensor?
Some other backround on the vehicle. I bought it from a dealer who got it at an auction around February from what the carfax said, so it was most likely sitting around all year. We added a bottle of fuel injector cleaner each of the last 2 tanks, but again, no missing or hesitation on this car once its rolling, its all during startup/idling.
One other note, I am hearing a loud rattling noise coming from what I think is the compressor for the ELC (behind heat shield directly above the muffler), it seems to be working but is making a loud noise 30 seconds after each engine start. Any ideas on that? Thanks in advance-Bill