RPM's DROP when turn on headlights?!? This normal??
 

I JUST realized this today. Turned my car on. Let it warm up. Idle at like 600RPM. I flick the headlights on and RPMs drop to like 300, car feels like it's gonna stall, then it catches itself, and goes back up to normal idle.

And I just had my alternator replaced with new belts!!

BTW, the same thing happens when I rev my engine with the headlights on. RPM's come CRASHING downward; feels like the car's gonna stall, but it never does. hmmmm....

:gotme:

Anybody know what's up with my max??

yea my car used to do that check the base idel... unplug the tps... start the car... adjust he IACV to ~650 rpm no load

yea what he said...

Cleaning your TB will resolve this issue. off topic, how much did it cost to replace alternator?

$400. parts and labor. i think i got ripped off.

BTW, i already cleaned my Throttle Body. Didn't help.

yea u got ripped off... considering the fact that the alternator is pretty easy to intall

actually this is how you adjust idle.

How to adjust IACV -

Warm the engine up to operating temp.
Turn off the engine.
Disconnect the TPS.
Start the engine and adjust the idle speed using the stop screw on the throttle body to 650 RPM's.
Turn off the engine.
Reconnect the TPS and restart the engine.

If the IACV is working correctly your idle should be correct. If it's a bit low, try adjusting the screw on the IACV bypass to get your idle speed to ~700 in neutral with no load. (no load means no lights or A/C)

the top screw on the throttle body? *runs outside and and pops hood.... returns to computer* Um, maybe i'm blind, but which screw is that? can't seem to locate it. What color is it? Any pics?? Thanks.

it's not on top of the tb. The iacv screw is on top of the iacv though. The tb screw is where the throttle linkage is it prevents the butterfly from closing fully.

If you just had your alternator replaced, and then it started doing this, I'd check your belt. Sounds like it may be too tight, causing too much drag. And then when the ECU realizes the idle is dropping too fast, it bumps the idle up. I'd loosen the belt slightly and see if it still does it. If it still does it, then I'd adjust the IACV. The belt only needs to be tight enough that it doesn't squeal when cold at idle. Nissan has a way of checking belt deflection in the FSM, but I do mine by letting it squeal, then tighten slightly till the squealing stops. My accessories still operate properly, and I know the belt isn't too tight.
If you adjust the IACV to bump up the idle and the belt is too tight, you'll still most likely have a dropping idle. And the belt will still be too tight, prematurely wearing out the bearings in the alternator and compressor. Been there, done that.

Just something to check, and it's free.

Dave

hmmm... interesting. Recently had the belts replaced, and the other day when i started up my car, the belt was squealing like a biatch for about 30 seconds. so ur saying that i need to loosen the belt?

if ur new belts are squeeling take it back to who you had fix your car, they should adjust it for free. i know i payed 450 (yep got ripped off) and i got it back and it would squeel, so i took it back and they adjusted it and its fine now. also i am having the same problem as you with the idle droping and i had the problem on my old alternator so that leads me to believe it is somthing else.

-Tom

Couldn't one always just upgrade their electrical system?! What about changing to hot-guage wire for the grounds?! Wouldn't that help a lot with the drop in RPMSs?! Sounds like an electrical flaw to me....just a thought....