Why Idle speed can not keep up?
 

I have trouble to keep the idle speed stable on my 323 protege 1990 SOHC 1800CC, I don't know if it's normal or not. Today I check the RPM with and without accessories as follow:

Idle speed with all accessories OFF = 1000RPM
Idle speed with headlight ON = 930 RPM
Idle speed with headlight and high fan ON = 880RPM
Idle speed with headlight, high fan and air conditioner ON = 650RPM

At 650RPM with all ON the engine is very rough, but If I increase to 750RPM when turn OFF all accessories the engine will rev. up to 1200RPM.

I think the ECU should keep the RPM stable as other car I have. Is the ECU gone bad? or maybe the speed sensor is bad? or maybe other sensor?:eek:

Please help.

RE: Why Idle speed can not keep up?
 

1000 rpm excessive for no load and the way rpm continues to drop without any compensation points to a possible fault in the idle control system. The Idle Air Control valve on the throttle body should be maintaining a relatively steady rpm. That is it's sole purpose outside of elevating idle rpm when cold. Sounds like valve may be stuck and PCM is unable to compensate for increasing loads. Might try disconnecting IAC with no loads and rerun your test. If still no changes then would definitely suspect faulty valve.

RE: Why Idle speed can not keep up?
 

I know it's very fast idle, but if I set it at manufacturer spec. of 750RPM will kill the engine if turn on the air cond. Sorry I have bad english, but where is it located the Idle Air Control Valve and also what is PCM and where to find it? Thanks for your help.

RE: Why Idle speed can not keep up?
 

The idle air control valve is located on the throttle body housing. It is probably faulty due to age or carbon build-up and needs to be removed and cleaned. The PCM (Powertrain Control Module) is the engine computer.

RE: Why Idle speed can not keep up?
 

Thanks bkey71, I will try to locate the IAC valve tomorrow and let you know.:)

RE: Why Idle speed can not keep up?
 

I still can't indentifier the Idle Air Control valve, I attach a picture. need help.

[IMG]local://upfiles/2724/8E4A837703124C6AA8BB5FD8EE97B582.jpg[/IMG]

RE: Why Idle speed can not keep up?
 

I already takeoff the air intake parts, but is this the Idle Speed Control you're refering to?

[IMG]local://upfiles/2724/456C9F2879F1419A84F2FB1987157A33.jpg[/IMG]

[IMG]local://upfiles/2724/CDC2D347F8354A1AA2C3973799B28A65.jpg[/IMG]

RE: Why Idle speed can not keep up?
 

That is it in the bottom picture. It may be possible to clean, but more likely need replacing.

RE: Why Idle speed can not keep up?
 

It has no ohm at all, so I pressume coil is bad as the circuit is open, have search the web for parts B55120660 but it cost $430 + freight + import tax will end up to $800, so I will try to fix it myself if can, otherwise will return it to the engine as is, and try to live with the high idle RPM.:(

RE: Why Idle speed can not keep up?
 

Sounds like an internal open in the winding if you have an open circuit. Should be around 10 ohms. Dealer cost here in US is $321.75.
Have you thought about looking into a possible used parts as well. Did a little digging and there looks to be some good matches for other years that use that part #. Protege and 323 with either engine from 1990 to 1994 all use the same IAC valve. Also show the 1993 Mx3 with the 1.6l 4 cyl uses the same part. No other matches that I could find in miata, 626, mx6 etc. Might be worth a look though.

RE: Why Idle speed can not keep up?
 

babyhuey bkey71, I really appreciate your help, I'm very happy because I already fix the open circuit of the valve, now I got 12 ohms and it's working as it should be:

Idle speed with all accessories OFF = 750RPM
Idle speed with headlight ON = 750RPM
Idle speed with headlight and high fan ON = 740RPM
Idle speed with headlight, high fan and air conditioner ON = 850RPM
Idle speed when the engine is cool = 1200RPM

The reparing is not so easy, mainly because the winding coil and the brass contact was completely fill with pressure injection black plastic, as ignoring where the wires are located I have to engrave the plastic very slowly in order not to damage the small wires. Also in order to remove the coil from the valve casting has to be first remove the return coil spring of which was epoxy clued to a small spindle, for the removar have to use mototool and micro torch and some dentis tools.

I spend a day for this project, but it is worth every minute.:D

RE: Why Idle speed can not keep up?
 

Very good!

RE: Why Idle speed can not keep up?
 

You must have the patience of Job quinto555 but it paid off. Nice work.:D

RE: Why Idle speed can not keep up?
 

Hello, I'm having a similar problem with my mazdaspeed protege. Its a 2003 though and has 39k miles.The thing is that I purchased my car with agarrett28 and my car stalls after revinghard or driving a bit fast. The RPMsbottoms outafter releasing the gas and it sometimes shuts off. The idle is steady athalf athousand RPMwhen it turns on and all, so I think it might be something with the idle air control. It has beengarage kept fora few months maybe this is contributing? what I really hope to get answered is whether it is the turbotimer or something pertaining to the turbo so thatI can take to to someone who knows about turbos rather then a mazda dealer. Any help would be great, thank you.

RE: Why Idle speed can not keep up?
 

I recently purchased a 2003 mazdaspeed and have had nothing but problems, the car wasprobably run witha nitrous system.nearly stalls out while idling, factory idle speed is 700rpms. already replaced the O2 sensor, along with the MAF sensor, still no help, thinking possibly the idle control valve, any suggestions from anybody??