idle drops when AC on

[Spades]

When I turn on the AC the idle drops about 500 RPMs and sometimes stalls. According to another site the idle is supposed to raise to 850 from 750 when turning on the AC. So far I've inspected the IPS (ground), TPS (logger values), ISC (resistance check), and throttle cable adjustments, and all seem to be fine. What other components are involved in maintaining idle? Car has no other idle issues when AC is not being used.

Currently, I have my idle set to 1300 so when i turn on the AC it will drop to ~800 but its getting annoying and Id like to correct it the proper way.

 

[1gDSM4g63]

The best bet it that you need to change your battery or check one your alternator.

 

[moto x]

I would get you alternator checked. Also check the B+ and ground of the alternator.

 

[Spades]

My alt puts out 14.1V, tested at the battery

 

[Spades]

I just thought of something... I wonder if my idle is actually normal when the AC is "ON", and maybe instead, I've got a high idle problem when the AC is "OFF"

 

[winterftbl]

I had the same problem and I changed my battery and alternator and now the problem is fixed. Hope that helps. Winter

 

[pdc]

I had the same symptoms. I changed out the ISC and problem solved.

 

[jongreene]

Try a new isc or atleast a working one, it sounds like its not compensating for the extra load.

If your near a junkyard you could pick up a few for free 99.

 

[Spades]

OK i ran some tests today, I monitored my logger at idle with AC off, and the ISC reads 11%, with the AC turned on it jumps to 30% which tells me the ECU is recognizing the AC being turned on. I then ohm'd out the coils of the ISC and each read 29-30 ohms, I also disconnected the ECU and ohm'd it from the harness to make sure the wires are good from the ECU all the way to the ISC, and they check out good as well. Then I checked my voltage with the AC on and its at 13.7V so I dont think its my alternator either... Im stumped

For you guys replacing the alternator or ISC and fixing your problems, were your original parts checking out good? I really dont want to go guessing and spending on an alternator, battery, or ISC as those are expensive parts to be experimenting with, especially when my tests are proving that my parts are fine

 

[BoostedinSoFla]

http://www.dsmtuners.com/forums/newbie-forum/275095-ac-fan-idles-fine-ac-fan-off-idle-surges.html

I'm having kinda the same problem. My ISC checked out fine though. I'm stumped too. I might replace the BISS though.

 

[tqmx1]

The ICS has a ball bearing inside it. If it dies and locks up the ICS is a dead player no matter how good it ohms out.

With that the only thing to do is a bit of junkyard hopping and get a replacement.

A lot of and our brother HYUNDAI have the same unit. don't tell anyone.

 

[Eclipsegst2312]

Double check all the terminals and cables for clean a good tight connections. Make sure you belts are all in good order and that the pulleys spin well. Start with the easy stuff and step by step eliminate things

 

[Spades]

PROBLEM SOLVED!!! I got lucky on this one, I actually moved on from this problem since the cold season is here and figured I'll look into it some other time, meanwhile I remembered a while back that my EGR thermovalve was bad and I joined the hoses together, well this weekend I decided to plug it instead, I thought nothing of it so I didnt even start the car when i finished, next morning when i went to work I started the car and seemed like no difference, then when I exited the fwy my idle was suddenly up to 1400RPM!!! On my way home same thing 1400RPM so turned down the BISS to about 900RPM and all seemed good....Then something dawned on me, I went to check on the idle with the AC "on" and the idle rose up about 100RPMs, exactly how its supposed to act. My ISC was fine all along as verified by my resistance check.
So here is the conclusion...my idle is not perfect yet, at times its slightly higher than normal depending on coolant temps (like after a long steady cruise) but this may be the result of the ECU having to relearn its parameters or fuel trims.

Ill update again in a couple days of any changes, but so far so good!!!