Query on iacv 95 940 t

[Cam205]

Have a no idle issue so have temporarily twisted the throttle cable to have a steady idle. Its past the ‘click’ of the tps.

Ive removed the bosch iacv and cleaned it and also tested it by adding 12v to it. It closes and when power removed it opens about 3mm. Is this normal operation?

Im tempted to buy a new one but for the money of a new bosch unit I wanted to ask and check if it sounds dud or are there other possibilities? All hoses are in great condition.

The ‘door/flap’ that moves in the iacv itself has lots of score marks on it and looks to no be able to open enough due to being old work. When I apply 12v should it open or close fully in either direction?

Are the cheaper iacv units worth a shot or should I stick with a bosch unit?

Thanks in advance.

 

[bobxyz]

Unplugged, the inner sleeve should have ~3mm opening - it's a limp mode. With power applied, the sleeve should rotate from slightly open, to closed, and then to fully open. You can use a finger, or small wooden stick, to rotate the sleeve manually. You can clean it with MAF cleaner, but stay away from carb cleaner/ brake cleaner.

 

[Cam205]

Unplugged, the inner sleeve should have ~3mm opening - it's a limp mode. With power applied, the sleeve should rotate from slightly open, to closed, and then to fully open. You can use a finger, or small wooden stick, to rotate the sleeve manually. You can clean it with MAF cleaner, but stay away from carb cleaner/ brake cleaner.

Ok thanks for the input.

I cannot move it any further open than the 3mm limp mode with quite a bit of force.

 

[hessam69]

What about the throttle body?

It is just as responsible for idling as the IAC valve

 

[Cam205]

What about the throttle body?

It is just as responsible for idling as the IAC valve

What about it? Ive adjusted it so I can have a steady idle at the moment and it seems to work fine other than not idling.

Im not overly familiar with the b230 throttle body workings. Are you suggesting I pull it out and clean it etc?

The car was idling fine up until about a week ago. I assumed the idle control valve that seems to be stuck would be causing the issues Im having.

 

[hessam69]

The throttle body and IAC valve both control the idle.

If the throttle body has never been removed to be cleaned, it will surely be blocked up, especially the tiny channels that allow bypass air through when the butterfly is shut.

Those are what the two brass vacuum line nipples are connected to.

 

[Cam205]

The throttle body and IAC valve both control the idle.

If the throttle body has never been removed to be cleaned, it will surely be blocked up, especially the tiny channels that allow bypass air through when the butterfly is shut.

Those are what the two brass vacuum line nipples are connected to.

Excellent. Ill look into that tomorrow.

Appreciate the write up.

 

[Cam205]

The throttle body and IAC valve both control the idle.

If the throttle body has never been removed to be cleaned, it will surely be blocked up, especially the tiny channels that allow bypass air through when the butterfly is shut.

Those are what the two brass vacuum line nipples are connected to.

Removed the TB and both holes were clear and clean. I sprayed some cleaner through them to be sure. It looked really clean in there.

So is this pointing more towards the IACV then?

 

[2manyturbos]

Removed the TB and both holes were clear and clean. I sprayed some cleaner through them to be sure. It looked really clean in there.

So is this pointing more towards the IACV then?

Maybe, indirectly. Have you checked whether your TPS is actually working? Not just hearing it click. Does it actually turn on/off? The TPS itself is the wear item in the idle control system. Those are actual contacts like a set of distributor points turning the IAC on and off. A sudden failure of the car to idle these days usually ends up being a failed TPS. The switch is ~ 30 years old unless it has already been replaced.

 

[Cam205]

Maybe, indirectly. Have you checked whether your TPS is actually working? Not just hearing it click. Does it actually turn on/off? The TPS itself is the wear item in the idle control system. Those are actual contacts like a set of distributor points turning the IAC on and off. A sudden failure of the car to idle these days usually ends up being a failed TPS. The switch is ~ 30 years old unless it has already been replaced.

This was my other concern as my Peugeot 205 Gti uses the same tps. Is there a way to test it with a multimeter? Or a more rudimentary way while on the car? Unplugged it today obviously to remove TB and forgot to plug it back in and results were the same connected or not. The car also runs perfectly at all throttle positions. Is my assumption correct that the TPS only really measure 0-50-100%?

 

[hessam69]

Yes you can test it with a multimeter, the readings should change as you turn the throttle

You can also bridge the middle and any of the outer two pins (with the connector not connected) and the idle should should come down. If it doesn't, the TPS is faulty

 

[2manyturbos]

Yes you can test it with a multimeter, the readings should change as you turn the throttle

You can also bridge the middle and any of the outer two pins (with the connector not connected) and the idle should should come down. If it doesn't, the TPS is faulty

That is not how the TPS works on LH 2.2 or 2.4. One circuit controls the IAC. The other circuit tells the ECU that the throttle is wide open. Both are simple on/off switches. Noting in between on the sweep of the throttle. When the throttle is closed the TPS circuit is closed turning on the IAC. Right off of the throttle closed position the switch opens turning off the IAC. At wide open throttle the other circuit is closed telling the ECU the throttle is wide open. That is used to clear a flooded condition. Wide open throttle with the starter being cranked turns off the injectors to clear a flooded engine.

 

[Cam205]

That is not how the TPS works on LH 2.2 or 2.4. One circuit controls the IAC. The other circuit tells the ECU that the throttle is wide open. Both are simple on/off switches. Noting in between on the sweep of the throttle. When the throttle is closed the TPS circuit is closed turning on the IAC. Right off of the throttle closed position the switch opens turning off the IAC. At wide open throttle the other circuit is closed telling the ECU the throttle is wide open. That is used to clear a flooded condition. Wide open throttle with the starter being cranked turns off the injectors to clear a flooded engine.

Thanks for the clarification. Tps seems to be doing its job so I have ordered a new Iacv. Hopefully it sorts the issue out. The car in question is in fantastic condition and all the contacts have clean and clear greased connections so hopefully its just a dud iacv.

Appreciate the help thus far to all involved. I will report back once the new part arrives.

 

[apollokid]

That is not how the TPS works on LH 2.2 or 2.4. One circuit controls the IAC. The other circuit tells the ECU that the throttle is wide open. Both are simple on/off switches. Noting in between on the sweep of the throttle. When the throttle is closed the TPS circuit is closed turning on the IAC. Right off of the throttle closed position the switch opens turning off the IAC. At wide open throttle the other circuit is closed telling the ECU the throttle is wide open. That is used to clear a flooded condition. Wide open throttle with the starter being cranked turns off the injectors to clear a flooded engine.

TPS doesn't turn ON and OFF the IAC, the IAC is controlled by the LH with PWM and its degree of opening continues to change during driving and not only at idle or when TPS opens or closes the circuit.
The TPS switch it is just one of the input that the LH uses to know when throttle is fully closed or not but the opening degree of the IAC is a function also of other inputs (rpm, engine load, climate and if I'm not wrong also vehicle speed)

P.S. the switch for WOT I remember that is used on NA engine but on turbos is ignored.