For some reason, I've found that the idle will jump & keep its idle a little above normal when I turn the headlights on. Nothing TOO noticible, but its there.

This also happens when I have heat on.

Can someone tell me why this is? It doesn't really affect any performance, I'm just curious to find why the lights affect the RPMs.

 

your charging system is failing under the load of your headlights, so the pcm tells the rpms to ramp up so the alternator will run faster.

check your battery and alternator for proper function.

 

If my charging system such as the alt/bat fails, will my battery light turn on?


Modified by tpot90 at 10:19 PM 5/5/2008

 

humm... My car does this as well. How do you check the charging system? I always thought mine was good.

 

This is normal behavior. The headlights are a large current draw and your charging system needs to ramp up output to supply the lights, which you see as a small increase in your idle speed. I'm not sure that you would see a similar increase when you turn the heat on, unless you're in defrost mode which turns on the A/C.

 

Right, under normal conditions, your ECU will signal your IACV to raise your idle when operating requirements dictate. This is most noticable when you do thinks like turn on your AC or sometimes even when electrics are turned on or the steering wheel is turned while parked. some of these things may simply be the engine idling faster from changing mechanical drag (like the power steering)?

In any case I wouldn't be worried unless it bogs and/or dies, indicating a too low idle or a problem with your IACV or ECU...

sohc