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Does anyone know anything about why my idle drops when I turn the rear window defogger on. Its really starting to annoy me. and I would like to see if there is a solution to it. Thanks in advance

Does car die/shut off? That is normal for idle to drop down since there's more load on alternator/electrical system. How low does it idle?

Yes but the engine should then rev slightly higher on its own to accomodate for the load and bring the idle back to normal (hence why big electrical loads waste gas). I believe a bad or stuck IAC would cause this.

I've had this same problem in one of my mx-3's for years... it's really not so bad for me since my idle is high anyways (over 1000) so I actually use it as an IAC so when I press it, it will drop the idle 2-300rpm

Mooneggs wrote:I've had this same problem in one of my mx-3's for years... it's really not so bad for me since my idle is high anyways (over 1000) so I actually use it as an IAC so when I press it, it will drop the idle 2-300rpm

mine has been idling at about 900rpm and the idle screw is turned all the way down and the TPS is adjusted. So lately I have been just hitting the defogger at it will drop down to the 650-700rpm range where it should be. But then everytime the car is re started the defogger turns off. and It is also not the correct way to make the car idle perfect. I will try changing the IAC tomorow as it sounds like it would cause the problem

My defroster turns off when you turn off the car as well. Correct me if I'm wrong but I thought that's the way it is on mx3s?

mx3autozam wrote:

Mooneggs wrote:I've had this same problem in one of my mx-3's for years... it's really not so bad for me since my idle is high anyways (over 1000) so I actually use it as an IAC so when I press it, it will drop the idle 2-300rpm

mine has been idling at about 900rpm and the idle screw is turned all the way down and the TPS is adjusted. So lately I have been just hitting the defogger at it will drop down to the 650-700rpm range where it should be. But then everytime the car is re started the defogger turns off. and It is also not the correct way to make the car idle perfect. I will try changing the IAC tomorow as it sounds like it would cause the problem

oh interesting mine is set the same way IAC all the way down, tps adjusted... definately post up what you find out - maybe I can get mine to work correctly too!

I think the idle will only go up if you select A/C. I'm going to pick up my modded 120amp alt this week. I want to see if it makes a difference with idle when I select stuff. I'll post back. If your idle screw is completely in and your idle is still high sounds like your TB is leaking, possibly a slight vac leak some where. Have you take the screw/pin out to see if any dirts in there or if the pin is maybe bend?

it's always been this way, idle drops when you hit rear defrost. the ecu does not compenstate. that's been a lil trick for a long time now for those with idle bouncing problems.. hit rear defrost and it goes away

ahhh more people coming out with the same problem! I have tried:
Different TPS
Different IAC (both cleaned with GUNK whilst stimulating the IAC)
Different manifolds - straight neck and curved neck

No luck!

what can it be...
bad grounds (though I have a grounding kit)
dying alternator?
corroded wiring
something different about a ZE IAC? cancel that, I'm running a k8 IAC atm
vacuum issues? I've always questioned the gaskets with my outlaw thermos...

And finally my red car with stock k8 DOES compensate for the demist, and idles beautifully regardless of extra load.

A good battery usually helps, make sure you alt is giving full juice ( I ve had alts giving 1/2 juice but not on my mazdas)

If that doesnt work maybe your RW def is drawing too much current, but that would be rare.

GL

I used to have this problem big time (to the point of stalling.. and it did stall once).

While it is still slightly lower then it should be, it's not that bad.

my solution?

replaced the fuel filter and ran some seafoam through the injectors.

marcdh wrote:ahhh
what can it be...
bad grounds (though I have a grounding kit)
dying alternator?
corroded wiring
something different about a ZE IAC? cancel that, I'm running a k8 IAC atm
vacuum issues? I've always questioned the gaskets with my outlaw thermos...

And finally my red car with stock k8 DOES compensate for the demist, and idles beautifully regardless of extra load.

it's not a dying alternator or bad grounds..
maybe old wiring - who knows
I don't think the IAC matters... I've used several different TB's including bored ones and it makes no difference

I think maybe it has to do with either vacuum or the ECU we are using (KL36 for me) I suppose I can find out this weekend if I try my kl36 in the other car...

Bump!

Im having the same problem as you mooneggs. Its really wierd, but has to be an electrical problem.

Has anyone fixed this issue???

bleh I got tired of trying to diagnose that soecific problem.. not my idle is all crazy, one day it will be high,. another low LOL oh well... lol other than that it drives ok lol