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Took off idle actuator hooked up to power and it simply vibrates - nothing moves? Seems like it's stuck? Car won't start. Is something supposed to move inside?
 

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The idle actuator is a rotating drum that varies, according to input voltage, the opening so the car idles around 800 rpm. Being that it gums up over time, just take some carburetor cleaner and clean it throughly. Clean up the contacts on the end with some fine steel wool and everything should work fine. You will be amazed at the amount of black gunk that comes out of that unit. The rotating barrel in side should move freely.
 

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Discussion Starter #4
Thanks

I have sprayed some in it and it still isn't moving. I am hoping over night might help.
 

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Here is what I sent you in email today:

Idle Actuator Control spring loaded rotary vane doesn't move until engine is started. My car starts up just fine with plug to it disconnected. It has nothing to do with starting car. I got a CEL with it disconnected but it still idled fine. It is used to set idle when you are slowing down at light, etc., not in starting car. Once I hooked it up again and restarted CEL went out.

You said you rewired/replugged it didn't you? Brown wire must be going to pin closest to intake and black wire goes to back pin closer to false firewall. Did you try to start engine with it disconnected?

I started my car with my IAC still in place and disconnected and my connector hooked to another IAC just laying on top of intake with key on rotary vane in it was closed. Once my engine started vane opened up all the way while my engine's actuator was disconnected and engine idled fine with no power to it.

As far a checking rotary vane and spring in yours you need to push shiny vane sideways against spring tension with a long pick (scribe) or narrow screwdriver towards what looks like to edge of vane because opening in vane actually on opposite side.

BACK TO YOUR NO START PROBLEM. Since car was hard to start before all this started and If coolant temp sensor wiring hooked up and no broken wires or slipped female terminals in 2-wire Bosch connector plug and same goes for 3-wire Bosch plug for RPM/Timing sensor you need to check both coil wire ends for corrosion and 1K ohm resistance and also pull distributor cap, check rotor for 1K ohms and condition of end tip. Also check inside dizzy cap for good center spring loaded carbon button (not worn out) and check 6 terminal contacts inside cap for corrosion.

Good Luck report your findings.
 

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Not sure I quite agree with all of that Steve. AFAIK, the actuator is used to control idle speed during all phases of operation. The fact that when you started your car with an external IAC plugged in, and it went fully open, suggests that the ECU wasn't happy with the idle speed and was trying to pick it up by adding some air. With no drive applied, these devices actually go slightly past their nominal closed position and allow some air flow. I take this to be a fail-safe design feature. Certainly, in colder climes, the IAC does an important job of adding air as the motor warms up. Unless ambient is very warm, I'd say a stuck one of these would make starting reluctant, unless some throttle was applied. The IAC also adds some air when the A/C clutch is active to hold idle speed.

Proof of this would be to monitor the drive waveform as the car is started and run. The drive is a PWM signal going to ground, so if you monitor the ECU side of the connector with the IAC in circuit (and assuming a solid 12V supply to the other terminal), you should see a square wave of roughly 12V amplitude with a varying duty cycle. At a guess, I'd expect it to be 60%-70% low at startup when cold, falling to maybe 40-50% low during normal idle. I've never looked, but it may well drop to nearly zero as soon as the throttle is opened. I'm not running Motronic on my 164 motor any more, so can't confirm (or refute) this. My 155 V6 has a slightly later ECU and a 3-wire IAC, so it's probably pointless using that as a comparison.

Quite agree about the way it rotates and reveals the air passage though ;) and they are prone to clogging up with sludge. They can be easily tested off the car too, just connect 12V across the pins, observing polarity, and it should open up nice and wide.

HTH, and as Steve says, tell us what you find.
 

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My car starts with IAC disconnected and nothing plugged into connector. Don't need IAC to start and just idle just as once engine up to operating temp you don't need coolant temp sensor to start car BUT YOU NEED IT COLD to be the cold start "injector/choke".

Try it sometime when engine warm and try it with IAC disconnected, too. I, also am from MO when it comes to this stuff so usually test it out first, then post.
 

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I agree cold starting without fully functioning IAC is difficult but as you say with a little throttle application it appears he was able to get car started if I understood his email correctly. I am shipping him one today to test in his 164 to see if it corrects his cold starting problem.

You are correct also about off "fail safe" position in that when "fully" closed the vane edge on opposite side from side that that opens via computer control it is very slightly open. That is why I can start my 164s with connector off when engines warm without hitting pedal slightly.

I think because it is showing slightly open in off position people think that it opens further from slightly open side and since rotary vane is spring loaded and really moves other way they think it is stuck when they can't get it to move.
 

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Found this waveform in a 'car data' CD. It also says that the duty cycle at idle is 30-50%. What it doesn't talk about is the IAC/idle control strategy.

Anyway, that waveform in case it's of any interest...
 

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Bosch documentation I have, states that start-up is controlled by varying the injector pulses and ignition timing.

What it does not say is that if there is no control of the IAC at startup you get the default 'fast idle'. (this is a supposition by me)

At no time in the documentation does it mention start-up and IAC in the same paragraph.
 

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Lets see if I get this right...if the car starts using only fast idle by controlling the injector pulses and timing, then the IAC is wide open. So when you turn the key on, the IAC should go to full open until it goes to closed loop and then vary according to the air/fuel needed to maintain idle speed. Right?
 

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yes on start it should be part way open. 100% seem a bit much but it might be.
when there is no power it goes to a limp mode and is open quit a bit on my car it will idle very fast like that.
it is what I like to say past closed to the point is opens again on the other side.
the rubber where is mates to the intake seem to be a spot for leaks. when that gets hard and the IAC move a bit it can leak causing strange idle problems. I would think starting would be easy with it unpluged.
I ran with it unpluged at first untill I wired up mine. but I run my own ECU.
I have it set to open 75% at -40°C and 65% warm for starting
it runs around 50% for normal idle on my car.
 

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So with a malfunctioning IAC the system may not start?
Possible not sure, but as I said my car started and idled with wire disconnected and IAC just setting in intake with hose hooked up.

Have you had your IAC off intake and hooked up to wire connector and turned on key to see if it opens part way? The one I sent you today does that.
 

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..... but I run my own ECU.
I have it set to open 75% at -40°C and 65% warm for starting
it runs around 50% for normal idle on my car.
Ditto. I have mine set to open to pretty much the same figures on my motor. Idle when warm is 49% on mine, but who's arguing over 1% ;) I also have mine set to increase the opening by 1% when the A/C clutch is pulled in. ECU controls this as well. When warm, my ECU uses timing to stabilise idle.

My memory of how the motor behaved with a fully functional Motronic was as follows; Crank - couple of turns later the engine would fire and immediately adopt a fast idle. This would then settle down to normal target as it warmed up.

If you had an IAC that was stuck on the truly closed position (rather than the fully relaxed state) I'd be surprised it if would idle unless you have an air leak beyond the TB or someone has adjusted the throttle abutment screw. Starting without added throttle would be difficult too I suspect......but try the IAC Steve has sent you and put us out of out misery please ;)

If this goes on much longer I'll be tempted to put a scope on a car I'm going to see this Saturday.....in fact, I think I will, just for the sake of understanding. OK, how does that sound? Any interest folks? I'll be working on a stock 164 motor with stock management. I'll take my 'scope and do some tests - any requests?
 

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Discussion Starter #17
Iac

I hooked mine up (Bosch connector only) and it did nothing - except make a humming sound. I will wait and see if car starts when I receive another IAC from Alfisti Steve.

:cool:
 

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I hooked mine up (Bosch connector only) and it did nothing - except make a humming sound. I will wait and see if car starts when I receive another IAC from Alfisti Steve.

:cool:
Try reverse the polarity! There is a coil inside. When there's current passing through the coil, a magnetic force will force the inside drum to rotate in one direction. You will not see any movement if the rotation is towards a direction that is already restrained (by the spring and some stop perhaps). The humming noise could be from some very small back and fore vibration.

But before you do this, use a small screwdriver and put it inside the air inlet side (not the sharp edge side) and see whether you can rotate the inside drum. I advise not to use any tool through the sharp edge side since the sharp edge and the drum surface can easily be damaged. This will jam the movement of the drum. If the drum does not move smoothly, try clean it with some carburetor cleaner (with the electrical side up to avoid the possibility of getting cleaner inside the electrical side). After it is dried, I usually put a couple drop of light weight oil inside for lubrication.

For the 12V(valves) IAC, there's two pins at the connector. A constant 12V(volt) is applied to pin 2 and the ECU grounds pin 1 to get the coil/drum to rotate. Since this is digital control ECU, it is easier for the ECU to issue ON and OFF signal than trying to set a certain level of opening. So the ECU will pulse (by grounding pin 1) at varying frequency to control the "duty cycle". There is a procedure that you can watch the IAC in action (see self-diagnostic Procedure B, 1-4-1-2). This procedure will activate the IAC and show you the IAC at 1 second idle and 1 second max speed continuously.

The later 24V IAC has 3 pins and there're two coil loops inside.
 

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I hooked mine up (Bosch connector only) and it did nothing - except make a humming sound. I will wait and see if car starts when I receive another IAC from Alfisti Steve.

:cool:
Please, please you need to verify you don't have wires hooked up backwards in connector before you hook up my IAC because as I remember you telling me you did some kind of wire repair earlier.

Remember brown wire goes to pin closest to intake and black wire goes to pin closest to false firewall.
 

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As threatened, I put a 'scope on the IAC drive wire on a stock 12V motor yesterday. Video is up in the usual place. http://www.youtube.com/v/fNEvgsgB4AI



From this, it's possible to see what happens on startup.

Ignition on - IAC gets roughly 20% open demand
Crank the motor - IAC gets around 90% open demand
Engine fires - IAC signal drops to around 50-70% open, as required, to maintain target idle speed.


But, the big question....is that bloody car starting properly yet?? ;)
 
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