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Non-Varioram Idle Stabilization Valve Replacement
 
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Pelican Technical Article:

Non-Varioram Idle Stabilization Valve Replacement

Time:

1 hour1 hr

Tab:

$300 to $540

Talent:

**

Tools:

7mm socket

Applicable Models:

Porsche 993 Carrera (1995)
Porsche 993 Carrera 4 (1995)

Parts Required:

Idle Stabilization valve

Hot Tip:

Clean the old one to see if the valve is at fault

Performance Gain:

Proper idle

Complementary Modification:

Oil Change

The Porsche 993 uses an idle control or stabilization valve to smooth out the idle. The idle valve controls the amount of air that bypasses the throttle valve and is variable to allow precise adjustments. The valve consists of a double solenoid; one for opening and one for closing the valve. A power supply is connected to both solenoids and the ground side of each solenoid and is connected to the DME. When the DME needs to change the position of the valve, it activates the solenoid by switching the solenoid to ground with a duty cycle signal, which creates a magnetic field that pulls the valve to the new position. The duty cycle value affects the position of the valve and therefore the amount of the air bypassing the throttle valve.

The idle control valve is expensive so before replacing it make sure you perform all neglected maintenance and check things like your O-2 sensors, injectors, MAF sensor and give the throttle body a good cleaning. Some of the problems like stalling on deceleration and stall stops can be caused by a dirty throttle body. The idle stabilization valve is also sensitive to ground faults so make sure to check and clean your grounds especially at the battery and under the driver's seat.

While lots of people will tell you that you can simply clean the heck out of the valve with carb clean and reinstall it; this is not a good long term solution. If you clean the valve and it helps fix the problem then you know that the valve is at fault and it should be replaced. Putting a valve that has been soaked in cleaner back into the vehicle may save you a few dollars upfront but the cleaner will eventually eat through to the coil wraps in the valve and lead to failure, and can on occasion lead to an electrical spike getting back to the DME. If cleaning the valve solves the problem that is a good diagnosis that it needs to be replaced.

The idle stabilization or control valve is located on the top of the motor in the center of the manifold (red arrow).
Figure 1

The idle stabilization or control valve is located on the top of the motor in the center of the manifold (red arrow).

Begin removal by squeezing in the metal clip on the wiring connection (red arrow) and pulling the connection off the valve.
Figure 2

Begin removal by squeezing in the metal clip on the wiring connection (red arrow) and pulling the connection off the valve.

The hose clamps can be in all kinds of positions depending on who worked on the motor last, and sometimes they are not in a position that you can get a screwdriver on (red arrows).
Figure 3

The hose clamps can be in all kinds of positions depending on who worked on the motor last, and sometimes they are not in a position that you can get a screwdriver on (red arrows). Use a 7mm socket and loosen the rear clamp first.

Pull the pipe towards you and off the valve and move it off to the side.
Figure 4

Pull the pipe towards you and off the valve and move it off to the side. Using the 7mm socket loosen the rear hose clamp (yellow arrow). You may have to slide the valve out from its rubber mount (red arrow) to help get the rear hose off the valve.

The hoses are different sizes so it is almost impossible to install it wrong but on the non-Varioram motors the arrow should point towards the rear of the motor.
Figure 5

The hoses are different sizes so it is almost impossible to install it wrong but on the non-Varioram motors the arrow should point towards the rear of the motor.

While lots of people will tell you that you can simply clean the carbon out of the valve with carb clean and reinstall it; this is not a good long term solution.
Figure 6

While lots of people will tell you that you can simply clean the carbon out of the valve with carb clean and reinstall it; this is not a good long term solution. If you clean the valve and it helps fix the problem then you know that the valve is at fault and it should be replaced. Putting a valve that has been soaked in cleaner back into the vehicle may save you a few dollars upfront but the cleaner will eventually eat through to the coil wraps in the valve and lead to failure and can on occasion lead to an electrical spike getting back to the DME. If cleaning the valve solves the problem that is a good diagnosis that it needs to be replaced.

Check the condition of both rubber hoses (yellow arrows) and lubricate the rubber grommet the valve sits in before installing the new one (red arrow).
Figure 7

Check the condition of both rubber hoses (yellow arrows) and lubricate the rubber grommet the valve sits in before installing the new one (red arrow). Installation is the reverse of removal and make sure that the valve is installed so the arrow is pointing towards the rear of the vehicle.

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