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Author Topic: Idle Air Control Valve  (Read 3597 times)

Kiwimagic

  • Jr. Member
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  • Posts: 63
    • 1990 SA SOHC, 1991 SA Verde DOHC, 1994 XR2 Turbo
Idle Air Control Valve
« on: June 29, 2021, 08:38:16 PM »

Hi All
I have a problem with my 1994 SE Turbo.
It stalls and will not restart until I remove the battery lead from the battery and then replace it again.
It will do this several times before it eventually stays running.
There is a noise coming from the IAC Valve which stops when I take the battery lead off..
Could be a solenoid opening and closing rapidly.
Seems to be worse with a cold engine.
This problem has only started since I fitted the Rocket chipped ECU.
Could it be a over boost problem. If so how do I remedy that ?
Im a bit reluctant to swap the ECU's over again as they are a pain to get to.
Any other suggestions ??

cheers
kiwimagic.
« Last Edit: June 29, 2021, 08:45:14 PM by Kiwimagic »
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greywolf27030

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    • 1991 XR2, 1992 XR2, 1993 XR2
Re: Idle Air Control Valve
« Reply #1 on: June 30, 2021, 04:00:33 PM »

The solenoid on the IAC is to increase idle speed when the A/C is turned on. Disconnect and see it that is the problem.
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Jack Byrd

Aus Capri

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    • 1989 Capri Turbo
Re: Idle Air Control Valve
« Reply #2 on: July 01, 2021, 04:21:31 AM »

You can bypass the IAC valve, disconnect the hoses from it and block the pipes. It will probably idle lower but you can raise the idle slightly on the throttle body. When I installed a chipped ecu (not a rocket chip) fueltronic chip I had problems with the solinoid valve thing in the vacuum line running to the fuel pressure regulator. It kept making it run lean. I just removed it and ran a vac line straight from the manifold to the fuel pressure regulator  and it sorted it out.

It may not be your problem but it's easy to remove it and see if it is the problem.

Hope you get it sorted soon!

Dave Robbo
« Last Edit: July 01, 2021, 04:23:33 AM by Aus Capri »
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Kiwimagic

  • Jr. Member
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  • Posts: 63
    • 1990 SA SOHC, 1991 SA Verde DOHC, 1994 XR2 Turbo
Re: Idle Air Control Valve
« Reply #3 on: July 04, 2021, 07:00:21 PM »

Hi
I have noticed a couple of things in my investigations.
1/. When the engine is running the revs occasionally drop off to around 500rpm and them pick back up to around 900 to 1000 rpm.
2/. When this noise is coming from the ICV and the engine will not fire ,When I disconnect the battery there is a quite a loud noise like a relay or solenoid opening or closing from around the MAF area.
Is the IAC controlled by the MAF ??

cheers
kiwimagic
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Rocketman

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    • 91 BPT AWD Capri & 1991 XR2
    • http://www.werbatfik.com
Re: Idle Air Control Valve
« Reply #4 on: July 04, 2021, 08:34:15 PM »

Swap the ECU back out. For testing you can just lay the ECU next to the console, you don't need to fully install it - just get it close enough to plug in.
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1.8L Turbo All Wheel Drive Capri... the "GTXR2"


Kiwimagic

  • Jr. Member
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  • Posts: 63
    • 1990 SA SOHC, 1991 SA Verde DOHC, 1994 XR2 Turbo
Re: Idle Air Control Valve
« Reply #5 on: July 07, 2021, 12:12:30 AM »

Ok...... There is more

I have fitted a "Y piece between the fuel filter and the fuel rail. 1 arm is to a pressure gauge and the other 2 arms have taps on them so I can shut them off individually to check for pressure leaks from both sides of the fuel line.
After running running the engine I have shut off the fuel from the filter and then in turn, fuel to the fuel rail. Both sides held pressure for quite some time but eventually lost pressure. But it took over 1 hour to do this. So I assume the injectors and the non return valve on the fuel pump are working reasonably well.
The next day.
Tried to start the car and no start until I realized that I had not opened the tap to allow fuel to flow. So opened the tap but car would still not start.
Ah..... There was that noise from the IAC .
After disconnecting and reconnecting the battery the mystery noise and no start problem gone .
Car starts and runs OK.
So the noise, and the "no" start condition both occur after trying to start the car without fuel pressure in the fuel line .
But why ???
Fuel pressure regulator problem ??
This is connected directly to the fuel rail and there is only a vacuum hose connected via a solenoid valve between the inlet manifold and the Fuel pressure regulator.
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greywolf27030

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    • 1991 XR2, 1992 XR2, 1993 XR2
Re: Idle Air Control Valve
« Reply #6 on: July 07, 2021, 08:22:57 AM »

I was thinking that fuel pressure isn't maintained in the system after the engine is shut off.
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Jack Byrd

Kiwimagic

  • Jr. Member
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  • Posts: 63
    • 1990 SA SOHC, 1991 SA Verde DOHC, 1994 XR2 Turbo
Re: Idle Air Control Valve
« Reply #7 on: July 08, 2021, 03:58:12 AM »

I have checked for a fuel pressure leak between pump and injectors and fuel filter to injectors  Fuel pressure (40 PSI) is maintained for over 1 hr after engine stopped on both sides..
It starts Ok after car has been sitting over night sitting. So I assume there is still fuel in the fuel line but just not under pressure.
Problem occurs when there is no fuel flowing when trying to start the engine. (Tap in fuel line closed)
Lots of air but no fuel condition. Must trigger something somewhere which causes the IAC solenoid to flutter.
When I open the fuel line tap, and disconnect and then reconnect the battery the noise (sounds very similar to a fuel injector working constantly) stops and car starts and runs OK.
There is no noise coming from the injectors only coming from the IAC.
When engine is running all the injectors work (tick) fine. 
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Aus Capri

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    • 1989 Capri Turbo
Re: Idle Air Control Valve
« Reply #8 on: July 08, 2021, 12:36:16 PM »

Check the flap in the air flow meter is moving freely. With the key in the on position you can turn the fuel pump on and off by opening and closing the flap. If the flap dosent move when your trying to start the car your fuel pump won't turn on.  Maybe it's a bit sticky and sometimes dosent want to open.
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Kiwimagic

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  • Posts: 63
    • 1990 SA SOHC, 1991 SA Verde DOHC, 1994 XR2 Turbo
Re: Idle Air Control Valve
« Reply #9 on: July 08, 2021, 11:27:52 PM »

Ok.....
I thought the info on cleaning the MAF sounded like a good idea. Couldn't do any harm.
So before I pulled the MAF out I unplugged the connector on the side.
Tried starting the engine. Nothing, Nada
When I disconnected and then reconnected the battery I had my Stethoscope on the main relay beside the radiator over flow reservoir.
AH !!!!! That is where the clunk is coming from when I disconnect the battery.
So that activates the IAC which stops the engine from firing.
But why I ask ???
Something is tripping that main relay.
Could it be the MAF as Aus Capri suggested.
Time to pull it out and clean it.
More investigation required.
« Last Edit: July 09, 2021, 12:38:02 AM by Kiwimagic »
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Kiwimagic

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  • Posts: 63
    • 1990 SA SOHC, 1991 SA Verde DOHC, 1994 XR2 Turbo
Re: Idle Air Control Valve
« Reply #10 on: July 09, 2021, 12:36:38 AM »

Mmmmmmm
After thinking about what "Au Capri" said about the MAF malfunctioning and not turning on the fuel pump.
Using the yellow two pin female connector under the windscreen wiper motor I made a jumper lead and put it in place.
With the key in ACC position the fuel pump worked and ran non stop..
Noise still coming from IAC,
Started engine, and it fired up straight away.
Removed the jumpers,
Engine starts every time now even with the noise coming from the IAC.
Once engine is running no noise from IAC.
Turn off engine, no noise from IAC.
Noise seems to be caused by a "NO" start condition.
   when engine is starved of fuel. (tap in fuel line closed)
   when coil is disconnected. (lead from dizzy unplugged)
   when MAF connector is pulled. (connector unplugged)
etc......
More investigation required.
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greywolf27030

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    • 1991 XR2, 1992 XR2, 1993 XR2
Re: Idle Air Control Valve
« Reply #11 on: July 09, 2021, 06:57:12 AM »

This is all very interesting information.
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Jack Byrd

Kiwimagic

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  • Posts: 63
    • 1990 SA SOHC, 1991 SA Verde DOHC, 1994 XR2 Turbo
Re: Idle Air Control Valve
« Reply #12 on: October 02, 2021, 07:52:41 PM »

I have removed the engine from the car. 
General clean up and fitting of the hybrid (VJ11 / VJ14) Turbo.
IAC Problem.
I have flushed the air connections on the IAC. When cold I can blow air through them. Then heated the unit up using a heat gun. The air connection was then shut off. When it cooled down again air could be blown through. So it seems the function of the IAC works fine. I have not as yet checked the electrical connections. Not quite sure how to do that, but working on it.
I did notice that the hose water line that comes from the heater unit via the firewall to the "J" tube did have two serious kinks in it that severely restricted the water flow. The person who replaced it just used a straight piece of water hose not a shaped "S" type. Each bend had collapsed and blocked off the flow. Hopefully this fix will cure the problem. Fingers crossed.
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greywolf27030

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    • 1991 XR2, 1992 XR2, 1993 XR2
Re: Idle Air Control Valve
« Reply #13 on: October 03, 2021, 09:54:15 AM »

Is the water passage though the IAC clear and is the hole in the block for the water clear?
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Jack Byrd