When car is fully warmed up and i turn my headlights on, i get the infamous hunting idle bouncing from 900 rpms to 1200 rpms. then when i turn the headlights off, it stays at a steady 900. I replaced the 3 main grounds (motor, trans, batt) and cleaned the surfaces and also tried 2 diffrent IACV which i sprayed both with carb cleaner and the problem still persists.

Also, when i rev the motor in neutral, it either takes a while for the rpms to get back to idle or drops down just below idle, revs back up a little then goes to idle. Already tried bleeding the coolant, tested the tps with a multimeter and tried 3 different map sensors and just got a brand new o2 sensor and CTS. HELP PLEASE!!!

 

First thing that pops into my head is voltage regulator.

Not sure about your second issue. Last time you did a tune up? Any CELs thrown?

 

^In think having the alternator tested would be a good idea.

What car do you have???

Also clean the IACV. Any CEL codes?

 

how would i go about testing the voltage regulator? last time i did a tune up was about 9 mo. ago but haven't drove the car for 6 months. the tune up was new spark plugs/wires, dist. cap and rotor, fuel filter and air filter (on stock airbox intake). for the 2nd issue, it doesn't really take that long for the idle to drop back to idle, maybe like 2 seconds.

I was thinking about testing my alternator but wasn't really too sure how to test it. How should i test it myself besides going to autozone ect. and having them test it? Also i tried 2 different IACV and cleaned them both before i tested them. I have code 41 (o2 sensor heater wire) I had one of those universal 4 wire o2 sensors that i needed to cut and splice together but i just bought a new BOSH o2 sensor that hooks straight up to the connector without cutting wires or anything but still throwing code 41. I'm thinking of buying a DENSO brand to see if that works.

Sorry forgot to mention its a Eg hatch with d16z6 swap on po6 ecu LOL. its just my daily driver.

 

Your Fast Idle Valve is out of adjustment. (this is the one on the bottom of the throttle body). Take it off, remove the two screws on it and turn the "plunger" clockwise until it stops and re-install.

 

Sorry forgot to mention, i cleaned and tightened the FITV also. I don't think that the problem though since its mecanically operated. idle bounces only when headlights are turned on. HELP!

 

you think code 41 (o2 sensor heater wire) cause this problem?

 

Hunting idle always says IACV to me. But then many factors are tied into the operation of the IACV.

The IACV exists to compensate for engine loads associated with accessories (lighting, A/C, etc.). It's like a little ECU controlled throttle valve that opens when your idle drops.

Not saying thats it, but maybe.

More than you ever wanted to know about the Honda IACV

http://www.gassavers.org/showthread.php?t=6478

 

The surging idle only happens when headlights are ON. Take your car to an auto parts store and see if they can check the alternator in car. Otherwise you have to remove it and take it to them for testing. It won't hurt to clean the IACV.

 

Also check whether 7.5A dash fuse 15 is blown.

 

forgot to mention that too lol. check all fuses under hood and under steering wheel by removing them one at a time and double check with a multimeter for continuity. I'm going to an autoparts store tomorrow to test the alternator.

 

well, alternator checked good. anymore guesses as to what else it could be?

 

bump!

 

bump again..idle still fluccuating when headlights on. it mostly happens only when the car is warmed up and headlights on. once i turn them off, it idles perfectly at 700 rpm's

 

I still say you have a charging system issue. Otherwise you might want to check the IACV and clean it even though the 2 are not really connected. Also the FITV if you have one.

 

Pull the air intake off to expose the throttle body. With the engine warm and idling, turn the headlights on to cause the idle fluctuation. Use you finger to cover the hole/port inside the throttle leading to the IACV. Does this stop the fluctuation? Do the same for the hole/port leading to the FITV.

 

Ron, i plugged the FITV port with my finger and idle was still hunting but it still had sucction. when i plugged the IACV port, the car died.

OFF TOPIC: is an 0bd0 alternator inter-changeable with 0bd1?

 

Bump

 

If the FITV pulls air when the engine is hot, then it needs to be cleaned and adjusted. When this is fixed, then set the base idle speed (see FAQs sticky). If the fluctuating idle problem continues, then the next step is to troubleshoot the alternator FR wire circuit.