Idle problem... well maybe...

[yontzie]

okay.. i have a mx-3 with a DE in it.... when i rev it up, even just a little. the idle comes back down and rests on 1100 RPM then after about 2 or 3 secconds it drops to 550 or 650... is it normal for it to stay at 1100 for a secc.?? just currious... PS. my buddy with a mx-3 ZE has the exact same thing.

[jmdearras]

I believe that is normal, to reduce emissions.

[navymx3]

My car runs normally at about 12-1500k rpm when its not surging....how do I lower the idle speed? I really have no idea, the idle screw is all the way down. advice?

[Newfie_dan]

to adjust the idle set screw you need to jumper pins 10 and ground in the diagnostic connector, thats the little black box by the firewall. You won't be able to set it with just the idle screw as the IAC will compensate for it. I would check for vac leaks and stuff and make sure the tps is adjusted right before adjusting the idle though. You may just be covering up the source of a problem if the idle is normally at 1200-1500 for you.

[navymx3]

So the black box has a bunch of plugs in it right? A bunch of fuses? how do you do that? because when I first got the car, it was idling around 1k, and Im not sure what happened.
And, would messing with the idle screw mess up the fuel air mixture? Would that cause a funky rpm? if so, how would i adjust that?

[Newfie_dan]

the black box is about 2inches square, its right up by the brake booster drivers side top of it should say diagnostic on it, some do some don't. It has a bunch of little squares in it use a paper clip or jumper wite to jump pin 10 to pin ground in that box, there should be a sticker with the pin numbers on it under the cover. Like I said check the other items on the list first, checking for vac leakas with a can of carb cleaner or throttle body cleaners spraying that along all the vacum lines and the throttlebody to see if the idle changes if it does then fix the vac leaks first. Top off your coolant when the car is cooled down, these cars are tempermental for coolant level affecting the idle. Make sure the throttle position sensor is properly calibrated then move onto the idle adjustment. Also make sure your idle air control valve is clean, remove the intake tube and open the throttle plate by hand and spray lots of it wherever you see black, especially the 2 ports are the lower portion of the throttle plate you will see which I am talking about when you look at it.

[navymx3]

I think I may have found the problem that my car started surging idle again...I blieve my IAC cable came unplugged?
here is a pic of a mx3 93 k8 engine i found on the net...its not mine, i havent taken a pic of it yet. but it should do?

its not the best quality..i did some MS paint to point out things im curious about.

[Newfie_dan]

Idle air control valve is located underneath the throttlebody has 2 small coolant lines and 1 electrical connector going to it. Your CAI as you call it is not in fact a true cold air intake, all you are getting from that is warm engine bay air. despite what other ppl may have told you, you do get more flow through it but without a bigger exhaust system the gains are very limited. Other than that you do have the right names on the locations of parts. A haynes manual or a good owners manual should hel you identify the locations of most all the parts in the engine bay.

[Daninski]

First, you can first remove the neg from the battery, depress the brake pedal for 15-20 secs. This clears the ECU memory and starts fresh.
Set your idle screw about 3 turns out to start with. With TEN and GRD jumped (can use a paper clip) start the engine then whenit's warmed up screw the idle screw in until the engine starts to die then screw it out to 650 rpm. Your done. Once you've done this shut the engine off, remove the jumper, start the car and let it run for a good 15mins so the ECU can relearn the new settings.

Question: The engine still has the K8 intake. Try to find a millenia intake, bigger runners. Better performance.

[navymx3]

Where is the ground? and where is the TEN where I jump the 2? And that isnt a pic of my specific engine. I put up a bunch of pics of mine in the "curious of what these parts are" thread.
And my idle screw, I have it turned to the right as far as it will go...is that bad? because what i saw was that turning it clockwise lowered the RPM.

[navymx3]

Just did a makeshift diag test with paper clip in the TEN and GND, and my engine light did a long pulse, and 2 short pulses. From what I read in the online manuel, that means my throttle position sensor either, "Throttle position sensor connector, Wiring from TPS to the ECM, Or TPS itself".
Expensive fix? could me cleaning out my throttle body with a whole can of carb spray really damage it? or maybe a wiring is not fully connected?

::Edited::
I was messing around with my car last night at work, a couple of my co workers were helping me, and came up with a possible answer...
When I was cleaning out my TB with Carb & TB cleaner, its possible that since TB cleaner doesn't dissolve rapidly like brake cleaner does, it could have drained down to the IAC, and possibly clogged it up, or is blocking the signal. So this weekend I am going to completely take off the throttle body, and take the IAC off, and clean it out with brake cleaner and compressed air, to get all the possible fluids and gunk out. So hopefully this will get the IAC working properly again.
I also have a video of my car running, and its very odd how, even when I unplug my MAF...the car is still working? wtf? Check it out. (Just click the image and it will brign you to the video.

[Newfie_dan]

With no maf the car will still run but in default or limp mode. If its working right you will not get any throttle response and it should throw a check engine light for sure. Check your coolant level as well, wait for the car to be cooled off and then pop the cap on the filler neck passenger side of the engine. If the coolant level is low it can trigger a surging idle and no check engine light. That sensor needs to be totally immersed in coolant to get proper readings and tell the ecm what idle to be run at. Carb cleaner or tb cleaner will not gum up the idle air control if you started the car when it was still wet as it will get sucked into the intake manifold, if there was a lot of gunk in the t/b then some of it could have settled in the iac. Carb cleaner usually won't damage the iac but thats not to say that some brands don't have some damaging chemicals in them. I usually prefer t/b cleaner as that stuff is a little gentler on seals. I am dealing with a surging idle like yours now after doing a thermostat and rad cap swap out. I am gonna check my coolant temp sensor later this week when I got time to see if the resistance is right on it or not. Seems like I am not getting great heat from the car either but mind you its damn cold here in canada as well lol, in -25 celsius thats -13 fahrenheit I get that surging idle once I am warmed up and I know my coolant level is full.

[Newfie_dan]

ok well I figured I would add this little update, I checked the resistance on my coolant temp sensor at 150 degrees fahrenheit and it was 316 ohms. Not the 1.84k-1.42k ohms I should have seen so its time to change that out. One thing I did note is that once I switched the heater to recirculte the air in the cabin it got much warmer than using the colder outside air only problem I ran into was my windows freezing up on the inside when highway driving. So I am gonna chalk my lack of good warm heat up to the cold ambient temp outside.

[Newfie_dan]

I figured I would update you guys on the car, so I installed the new coolant temp sensor and dialed in the idle again since it was out of whack with the new sensor in. Idle is much better, sits at 650-750 steady now and she idles down to normal much faster than before with very little hesitation at 1000 rpm when I stop, it sits at 1000 for a few seconds then drops to 650. Before the new sensor I had to wait like 30 seconds or so for it to drop or drag it down with the clutch. No more dragging it down now. I am quite happy with the results, I will keep you guys posted once the temp drops again to see if there is any difference in the colder weather.