I have an 02 protege, when its idle in "drive" the rpm goes down to 600-650 and becomes rough.

However when i decide to turn the heat/cooler fan all the way up, the idle becomes smoother and goes back up to 900.

Guys I need a clue thanx.

 

Does the idling bounce up and down between oh, 600 and 800?
I don't know how familiar you are with your car yet but when you turn the dash setting to any defrost combination your a/c compressor comes on, and that bounces the idle around. Still it shouldn't be running too rough at low idle.
How long has it been since the spark plugs were changed?

 

Well also any time you turn on a device inside your car- heater, stereo, AC, hell even your lights to some extent- the power usage of your car changes. Which changes how your car idles.

Its perfectly normal

 

All i know, is that I stop at the red light the rpm is at 600 rpm and its rough.
I changed the plugs and wires 2 weeks ago.

one garage told me to go to the dealership. so i dunno

I dont think this is normal.

 

Check your EGR valve. It's a pretty common problem that causes rough idle. There's a how-to writeup
HERE on how to go about doing the removal and cleanup.

 

What brand of plug did you use?

 

I used NGK plugs and wires

 

Check all your hoses for vacuum leaks? It's an easy thing to overlook sometimes ..

EDIT: What he said VVV + check vacuum leaks & EGR buildup

 

Sorry misread the first post. A rough Idle isnt normal no. a change in the Idle when the heater is on compared to off is normal. Sorry though- as for a rough Idle- I am not 100% sure why. Plugs are good? fuel system is clean? Air filter clean? Oil changed? basicly maitenance isnt an issue?

 

I'd like to start with the simple things. Did you replace the wires one at a time?

Do you have a check engine light?

 

I had extremly rough idle on my 01 SE. Needle bounced up and down, heard sputtering. Had the EGR changed, so far the prob is over. Oh yeah I had the Check engine light on.

 

One way you can check for a sticky EGR by tapping it with a small hammer. If the idle comes back to normal you have the culprit.

 

The rpm doesnt bounce up and down, it just slowly goes down to 600-650 and the car is not crazy rough, its a slight vibration of the fact that its idling soo low. When I put the heat/ac fan all the way up the car idles at 850-900 and its very smooth...I just want it to be that way.

Ill check the egr and the hoses, thats all great advice.

 

I just delt with the same problem on our 2003 DX. Turns out, Mazda did a stupid thing with the design of the heating cooling system. When you turn the selector **** to FLOOR, or any of the DEFFROST settings, the AC will come on, but the AC indicator light DOESN'T come on. But if you listen closely, you'll hear the AC clicking on/off when it's on these settings. This bogs the motor down and caused our car to stumble when pulling to a stop.

I had Mazda look into it and they replaced the heater control valve (what ever that is) under warranty, but it continued to do the same thing. So they called Mazda Tech for advice, and that's when they were told that "the air conditioner was supposed to engauge on the FLOOR setting". It seems that Mazda had problems with the Protege's windows fogging up in the winter, so they added this "feature" to fix the problem.

The dealership ended up turning my idle up a little bit and I don't put the selector **** on the FLOOR setting anymore in the winter. That "fixed" it I guess.

Hope this helps!

 

What do you mean keep the setting on FLOOR?