Idle Control Valve (Error Code 33)

Symptoms;

- Lumpy Idle (~0 - ~900rpm)
- Cutting Out When Clutch Depressed

I'd like to begin by saying that this is my first Impreza and I may have made things more awkward for myself or the process longer so anybody who knows better please do step in. I won't be offended by any alternative methods.

I wrote this guide as my ICV was faulty and after a couple of hours searching the net I had no luck. I am new to Imprezas and don't know my way around the engine bay so I thought this would help others who needed to sort this problem.

This replacement was on a '98 JDM Import Version 4 STi - it may not be the same process for earlier or later models.

Step 1 - Identifying the Idle Control Valve

When stood looking at your engine bay, the ICV is located to the right of the throttle body on top of the inlet manifold. It has a pale brown cover and grey connector clip attached;



Step 2 - Disconnect the Battery!

Always disconnect the battery before working in your engine bay, especially when removing electrical connectors and coolant/fluid lines.

Step 3 - Remove the Intercooler

I found that the easiest way to access the bolts on the back of the ICV was to remove the intercooler. This consists of;

3x Jubilee Clips
2x 12mm Bolts

Firstly, undo the jubilee clip that connects your dumpvalve (or standard recirc valve) to the intercooler and remove. Then undo the top clip that holds the intercooler to the throttle body, and lastly undo the jubilee clip on the turbo outlet;



Now that is done all that is left are two 12mm bolts (circled below) that hold the intercooler in place. Undo both of these and lift it out of the engine bay. It will require some wriggling and tugging but you'll get there.



Step 4 - Removing the ICV

This consists of;

3x 10mm Bolts
2x Hose Clamps (you'll need pliers)

For this part you must unclip the grey connector from the ICV. One that is done there is a big air line from the induction pipe that runs to the top of the valve, remove it.

In the picture below you can see the connection for the big air line at the top (pointing diagonally top-right), the two coolant lines (mid-lower left and mid-lower right) and two of the 3 10mm bolts (top left and bottom right), the third bolt is obscured by the air inlet;



The two coolant lines running to the ICV need removing so be careful, if you're too heavy handed you'll spray coolant everywhere. Use the pliers to slide away the hose clamps and gently pull away the coolant lines. I blocked them off with the 2x 12mm bolts from the Intercooler bracket.

Now all that is left are the 3x 10mm bolts holding the ICV to the Inlet Manifold. Two on top and one on the bottom right corner as seen in the picture above. A 10mm socket with an extension bar will do the job.

Here are the bolts removed;



You will have noticed that the bolts are different lengths. The longer two are the top bolts and the shortest is at the bottom - it's important you remember this when you refit your replacement ICV.

If you don't have a replacement gasket be very careful when removing the old one. It's not recommended to reuse it but I managed to carefully seperate mine from the fauly ICV without damaging it.

Step 5 - Refit your New Valve

Congratulations, you have successfully removed your ICV. Fitment is in reverse order.

If you find that your car is suffering from white smoke from the exhaust after this replacement, the gasket between the ICV and the inlet manifold has failed and is mixing coolant into the inlet.