ahyc84

All emission crap removed, so i assume it should be running rich. It keeps doing this even after idling for an hour. It bounces between 1000-1300rpm. This is a turbo 13b btw.

I've thought it was the TPS, replaced that with one that's tip top in spec

I also thought it was vacuum leak for the longest time. But i've hooked up my air compressor to the piping right after the turbo pumping 10psi. I dont hear any leaks. I assumed any leaks that can cause it to have bouncy idle would have some sort of sound at 10psi. I've checked this probably around 5 times now thinking i must have missed some sound.

So with those 2 main thing nailed down, i'm taking a stab at the tuning or possibly some sort of wiring. Now here's the MAIN thing that really entertains me.

When the oil are all warmed up and all at a stage where a normal car would idle normally, it does the usual bouncing thing of course. HOWEVER, when i press the clutch pedal down just a tad. (Not enough to have any actual pressure on the pressure plate. This is basically the free playing area of the pedal before you feel any pressure) The bouncing idle stops and it idles perfectly between 1000-1100rpm. It'd idle perfectly until i release the clutch pedal pass the area you'd feel pressure from. Ya i know this is still a little high.

So in another word, as long as i keep a foot on the clutch pedal keeping it out of the pressure less area, the idle stays at 1k. Any master knows what's up with this, or anyone has dealt with this before? Is there some sort of sensor at the clutch pedal\line somewhere that might have a bad ground or something?

Once it's warm enough, i'm gonna tear the interior apart again and redo the big mess of wiring, and standalone going in soon. So i'm trying to figur out what other possibilities it could be before causing more trouble by tearing it down haha


thx for any help
-Adrian

Kouta

This exact thing happened to me. Press down the clutch bairly and the bouncing would stop.
I loosened my throttle cable in hopes to drop the idle to something sub 1000rpm when it was steady... and it went away... so i rechecked my tps and rechecked my timing just to be safe. I have no idea if its the same thing for you... just saying what finally killed mine.

ahyc84

hm. loosen the TB cable as in the adjustment on the actual cable and not on the TB? like the 2 adjustment hex on the cable before it attatches to the throttle body?

cuz now that u mentioned it, i think i might have touched that at one point or another when my upper intake manifold was taken off many time to find a leak heh. I'll give that a try tomorrow after work. My neighbor would kill me for starting my car right now.

I completely forgot about that adjustment on the cable, since i was implanted with the idea that I only have 1 idle adjustment after doing the TB mod and emission removal.

thx dude. will get back on this with result tomorrow


this still doesn't really explain the whole pressing clutch and idle smoothing out thing....

classicauto

iTrader: (3)

so when you press the clutch down that little bit.......does it JUST become a solid idle? or does the RPM drop to 750-800 and idle?

HAILERS

The function of that lower clutch switch isn't really that clear in the fsm (S4).

It's a dual function switch. When depressed it puts 12v on a wire in the Cruise Control Unit if you have one, and disengages the cruise if in cruise.

The second function is to send a 12v signal to the ECU pin L (S4). Why? and What it does isn't clear to me. We know that the AWS or that approx 3000rpm for 17 seconds can be avoided by depressing the clutch pedal, so it would seem to have something to do with engaging/disengaging the AWS. That makes sense because you wouldn't want to jump in the car, fire it up an drive it right away with the engine at 3000 rpm. It sort of cancels that AWS for 17 seconds out for that case scenario.

In other words I'm not 100 percent sure of all that 12vdc signal does internal to the ECU other than the AWS.

If your thermowax and fast idle cam still exist, then I'd see if they are holding the throttle linkage open and not letting the Primary throttle plate return to full close.
Also if the water thermowax still exists on your car, make sure the water is flowing thru it to make the thermowax work right.

One thing you might try is to pull the plug off the bac and see how much the idle drops and how much less bounce you get if you do that. In fact I'd try that first.

Removing the airpump, acv, cat etc does not effect the fuel mixture.

RETed

Rich AFR's will NEVER cause a bouncing idle.
Too much fuel will cause lower idle to the point the engine will die due to fouled spark plugs.
You're barking up the wrong tree if you think the engine is running rich at idle.



-Ted

ahyc84

JUST solid idle at 1000-1100rpm ish.

heh, all of these are gone. It's a turbo s4 13b with no emission controlling devices, and or any sort of car warming convient gears like the thermowax. Basically as bare as it could be to make it stupid for driving on the street heh

ya i know too rich owuld just drown it out n e ways and backfire and what not. It does that occassionally idling. It's just one of the thing i figured i'd mention since this could all be possibly a tuning problem with a bad sensor or something.

1980's 7

Don't mean to Hi-jack but...

I have a similar problem. It's just the opposite. The car bounces(not really bouncing, but HmmmmmmHMmmmmmHMmmm erratically) around 200-300ish but when I step on the clutch pedal it raises up to around 500-600rpm. And if I turn on the AC it goes up even more, it still can't reach 750 but it does settle down a bit.

ahyc84

ok so a lil update.
I did the throttle cable thing on the cable adjustment itself rather then on the throttle body, played with that, barely did any difference. Got the car to idle a little lower though. Still bouncy.....

Sooooooooo since i remebered someone mentioning about the sensor for the clutch, i got under the dash, and unplugged the bitch. The car no longer does the bouncy thing. yay improvement. BUT it still idles a little rough. So i'm assuming my clutch sensor is a dead pos. w/e, i don't use cruise control, it's not even installed. I need the car completely warm before driving it anyways.

The rough idle jumps around in a range of about 250rpm. This depends on the position of the Idle Mixture Variable Resistor though. Rich = lower idle, lean = higher idle. I could get it to bounce as low as 700-900ish, or as high as 1000-1200. This isn't like the regular interval bouncy thing from before unplugging the clutch sensor. The thing is though, when i get it to the richest setting, I have to go WOT for the car to start. Or else it'd just keep cranking but not fire.

I then took a look in the FSM for the spec of the variable resistor, apparently pin A-C & B-C should be 0.5-4.5k ohms
Guess what!
A-C is completely dead. Stays at like 5ohms or something regardless where i turn the resistor.
B-C is sort of in spec, but it goes lower then 0.5, and it goes as high as 5.1


so in the end, another broken piece. arrrrrrr. Sending an email to the mazda dealership to get a price. Hope it won't be too much.
I think Microtech LT10 controls the idle mixture though. Gonna have to double check on that.

ahyc84

ok um. went outside again to chk some stuff, the car fired up with out having to go WOT. Idles at between 680-800rpm. Isn't that still a little rough? I know rotaries idle bounces around a little more then the piston ones considering the piston idle just stays dead on at 800rpm or so.

When i had to go WOT to start the car, the engine was all warmed up. Let the car cooled for like 20min before i started again just 5 mins ago, and it fires up fine. hm

ctsupacat

I had a fluctuating idle issue myself when my car was stopped and the clutch was engaged. I called a rotary specialist and he suggested the clutch switch might be bad. Turns out I had a broken spring in my clutch switch which is located behind the clutch pedal. All you have to do is unscrew the clutch switch from the pedal and open the switch using a flat screwdriver. Inspect the switch, clean it with alcohol and make sure the spring is in one piece. If not replace the spring and you should be fine. Or you can just purchase a new clutch switch- shouldn't be that expensive.
Also make sure your idle is @ 850 rpm in neutral after the car is warmed up (drive for 10 minutes). adjust idle screw at top of manifold with black rubber cap. Clockwise to idle down... and counter-clockwise to idle up.

My idle is PERFECT now!