The-T-Bar MGF Forum

I have been having odd engine idle problems with the engine warm.
Sometimes the the revs have been cycling between 200 and 1500 revs(Hunting). Sometimes staying at 1200-1500 revs, as if the 'choke was on'

There are a number of things that can cause the idle to stick higher.

You could have a sticky throttle cable.
You could have a sticking throttle body(usually only the plastic ones)
You could have a gunked up Idle Air Control Valve.

There are a few things that can cause hunting.

You could have an air leak on the inlet.
You could have a gunked up IACValve.

The probability for my symptoms seemed to point to the IACV. Now, there are two types fitted, the earlier one, which you can disassemble and clean; and the later one, which is one piece.

The Iac valve is also known as the STEPPER MOTOR.

Mine is the later version.

To access the valve you will need to remove the engine access panel See HERE.
Or HERE if you have Satur type hoops fitted.

Now you will be able to see the IACV on the inside of the inlet manifold.

First unclip the electrical connector.

The IACV is held to the inlet manifold with 4x t30 torx bolts.

The top two are accesible, but the lower two are more awkward. I managed to reach them all with a small 1/4 drive socket.

Now you can remove the valve from the inlet manifold. It is sealed to the inlet with an 'O' ring in the face of the valve. Ensure that it does not drop out, when removing it.

You can now separate the valve from its tubing by simply twisting and pulling. Leaving you with this.

It is possible to clean the internal piston and seat of the one piece IACV, by using spray carb cleaner directed into the orifices.






However my efforts in this direction resulted in the problem becoming worse, so I bought a replacement IACV.

Refit the valve ensuring that the 'O' ring is in place. Replace the four torx bolts. Refit the tubing, noting that the connecting tube has a mark to line up with the ridge on the valve.

Tighten the bolts and refit the electrical connector.

Start the car and check that the idle is stable before replacing the engine access cover.

The earlier IACV looks like this. It is removed/replaced in the same way.

It disassembles easily, allowing you to see what needs cleaned.

It should look like this.

david aiketgate wrote:


It is also a good idea to take off your air filter connection and spray this cleaner into the throttle body. This will clean up the induction internals.

Only do this when you have refitted the valve and can start the car, as you will need to rev the engine to prevent it stalling. Once the engine is ticking over smoothly again you can 'hide' the engine again

Just a quick update:- The symptoms have disappeared. Woohoo! An added bonus is that the tickover is now much smoother.

How fully move back the plunger of a monobloc IAC valve in order to clean it properly?
Is it true that when you turn the starting key in position II, the plunger moves back full open to help the engine to start?

Titanium wrote:

If you take off the valve from the inlet manifold but keep the electrical connection, you can get someone to turn the ignition to II and the piston will move enough to allow you to give it a good clean with carb. cleaner.