idle drop when turning on headlights

[TI-driftin]

Any ideas why my idle drops when i turn my headlights on?

I just replaced the battery and autozone tested my alternator and said it was good. I used to have some idle probs but i replaced the hoses and my intake boot and that pretty much took car of my idle problem. Although i didn't replace the ICV. Occasionally i still have a slight idle bounce when i come to a stop light.
Is it possible that the ICV needing replaced could affect my idle dropping when i turn my headlights on or is it something else?

[cooljess76]

Originally Posted by TI-driftin

Any ideas why my idle drops when i turn my headlights on?

Is it possible that the ICV needing replaced could affect my idle dropping when i turn my headlights on or is it something else?

Possible, yes. Likely, no. First off, do you have an aftermarket stereo system with amps and subs? If so, try disconnecting the system from the battery, or simply pull the fuse and see if the problem persists. Second, are your headlights OEM or aftermarket such as Depo's, ZKW's or Apexcones? Shouldn't matter either way as the bulbs draw close to the same amount of power, but there may be an abnormal drain somewhere in the system if you've swapped them out. Also, your alternator might test good even though it's on it's way out. If it's the original alternator, there's a good chance that the brushes and/or voltage regulator are worn. If you have a multimeter, check that it's putting out a steady 13.5v-14v at the back of the alternator, then check the voltage at the battery. 11v-12v IS NOT ENOUGH. Sometimes shops will see that it's putting out 12v and say that it's good when in fact it requires a little more juice for our cars. Finally, I would recommend checking your main engine ground. It's just behind your passenger's side front wheel well. You'll have to access it from under the car. There's a wire that connects the passenger side motor mount to the chassis. Check the continuity of that wire, maybe take it off and clean it with a wire brush. Check continuity of all the wires in the vehicles charging system for that matter and report back. Good Luck.

[Bobbak]

Originally Posted by TI-driftin

Any ideas why my idle drops when i turn my headlights on?

I just replaced the battery and autozone tested my alternator and said it was good. I used to have some idle probs but i replaced the hoses and my intake boot and that pretty much took car of my idle problem. Although i didn't replace the ICV. Occasionally i still have a slight idle bounce when i come to a stop light.
Is it possible that the ICV needing replaced could affect my idle dropping when i turn my headlights on or is it something else?

trust me check your spark plugs

[TI-driftin]

Originally Posted by Bobbak

trust me check your spark plugs

I got brand new plugs and wires and engnition coil and ECU and and and. haha sorry. They all went out at the same time because i had a gasket leak and got oil in the spark plug area. But what i was getting at is i had this problem before i changed my plugs.

Cooljess,
Sounds like all of your advice is right on. makes sense. I will try to disconnect my sub amp first and see what happens. Its a class D so i think it draws quit alot of juice. Plus i dont remember having the problem before having the amp in there. I'll let you know what happens.

[TI-driftin]

ok i disconnected my power wire that runs to my amp and i still get the idle drop when i turn my headlights on. I didn't use a multimeter to test my alt but my stereo has a volt meter on it and it says 13.2 when running and 12 something when off. I guess the only thing left is to check the engine ground.

[xxxJohnBoyxxx]

Originally Posted by TI-driftin

ok i disconnected my power wire that runs to my amp and i still get the idle drop when i turn my headlights on. I didn't use a multimeter to test my alt but my stereo has a volt meter on it and it says 13.2 when running and 12 something when off. I guess the only thing left is to check the engine ground.

How much of a idle drop?

It is normal for a slight drop in RPM since when you turn on the lights it causes the alternator to take more HP to spin it to keep up with the amperage demand. 13.2 volts is acceptable. My car drops about 50 rpm when I turn my lights on and I have no electrical issues.

[TI-driftin]

not sure. I'll check tonight. I think its more than 50 though. One time it almost killed my car when my fan came on but its not that bad anymore.

still gotta check the engine ground too.

[xxxJohnBoyxxx]

Originally Posted by xxxJohnBoyxxx

How much of a idle drop?

It is normal for a slight drop in RPM since when you turn on the lights it causes the alternator to take more HP to spin it to keep up with the amperage demand. 13.2 volts is acceptable. My car drops about 50 rpm when I turn my lights on and I have no electrical issues.

Well I'm quoting myself because I gave bad information. 13.2 volt is not acceptable. I have the same problem as you. My car charges at exactly 13.2 volts and I have the idle drop with lights on and voltage goes to 11.6 volts. Additionally my windows stop about half way up on auto up for the past year. I started thinking about it and checked my battery and it was not fully charged. A fully charged battery will read 12.7 volts with no load on it. Mine is around 12 volts with no load. It is not the battery since it is new. I put a charger on it and it fully charged the battery. After the charge it was 12.7 volts with no load. Now the windows work correctly after the charge with engine not running, first time in 1 year. I think it's the regulator in the alternator going bad. I believe the voltage should be between 14 to 14.7 volts when driving which neither of our cars are doing so the battery never gets a full charge. I'm sorry for giving the bad information (the worst thing you can do in a forum) but I believe you need to replace your alternator as do I. All my grounds are perfect but still check yours before you purchase and change the alternator...Thanks, John Smith