Strange RPM Drop
 

Ok, so if I let the car idle with nothing on (headlights, AC, etc) she purrs like a kitten. If I fire up the AC, the rpm's will drop to the point that sometimes it dies. The other day I'm sitting at idle on hot day, and the front cooling fans kick in...rpm drops then it starts hunting for idle. Today I discovered simply turning the headlights on will cause a drop of 200 rpm, then the hunting for idle begins again.

Certainly sounds electrical to me, but not knowing much about the electrical systems in these cars, I thought I'd better ask before I start replacing expensive electrical items.

Any thought would be appreciated.

your throttle body [idle air controll] maybe coked up.....a scan tool may help to see if its trying to move

Found an interesting article on the problem. Seems as if there is NO FIX for it.
ARTICLE

I think I've had something similar happen to me twice under similar conditions. It only seemed to happen on the initial start up if the A/C was turned on. It was nighttime, so my lights were on as well. The engine would idle very low and then raise the idle to 1000rpm or a little more and then drop again. I watched this happen three times in succession the last time it happened, and lightly tapped the gas pedal to make the idle rise a little over 1000rpm. The car seemed to idle normally after that. Certainly not a fix, by any means, but I figured I'd comment even though this doesn't appear to be a consistent problem for me.

It seems like it has to do with the engine being overloaded by having to run the A/C and lights, but I would think that with a strong battery, and just by design, the car should be able to handle that without nearly dying or struggling. However, I also am having an issue with my lights, both interior and exterior, flickering while the car is running or when activating lights by doing something like stepping on the brake, so I'm not really sure if that is related to the problem described in this thread in my case.

Have your alternator checked...sounds like it's not keeping up with the draw down on the battery.

Heya, jcb, if that was directed to me, that's currently in the works, as that was my suspicion from the moment I noticed the problem. :cheers:

Sorry to revive old post
 

Did a new alternator solve it?

I agree. I charge my battery every week or 2 and it needs it. Runs nicer when charged. Full voltage feels better with a/c running. The PO's wife drove it everyday to the gym (YOGA !!!) but at my home the car stays in the garage all the time with the battery discharging.

Try this first before taking your alternator off your cars to test.

Amazon.com: Equus 3721 Battery and Charging System Monitor: Automotive

When you suspect an electrical problem, it is not easy to tell if it is the battery or the alternator. This tool can help you determine which.

I like it so much that I bought extra and give it out as gift. :)

If you join Amazon Prime, the 2-day shipping is free too. (There are so many "free" things AFTER you pay!!!)

Thanks Mikehkang, Just got 2 in the mail today. (equus 3721). One for brother in law for xmas. The 3721 works good ! Charging at 14.01 @ 2k rpms