Porsche Parts Catalog Porsche Accessories Catalog Porsche Technical Articles Porsche Tech Forums
 
  Search our site:    
View Recent Cars  |   Cart  | Project List | Order Status | Help    
 >  >
Idle Speed Adjuster Replacement
 
Bookmark and Share

Pelican Technical Article:

Idle Speed Adjuster Replacement

Steve Vernon

Time:

4 hours4 hrs

Tab:

$350 to $550

Talent:

**

Tools:

Flathead screwdriver, 10mm wrench, punch, 6mm Allen

Applicable Models:

Porsche 944 Turbo (1986-89)

Parts Required:

Idle speed adjuster and hoses

Hot Tip:

Tap the manifold with a rubber mallet to free it up

Performance Gain:

Proper engine function

Complementary Modification:

Check for vacuum leaks

The idle speed adjuster on the Porsche 951 is an electrically controlled valve, which gets its input from the Bosch Motronic DME, which is linked to the KLR or knock regulator unit. The valve is fitted so that it bypasses the actual throttle body. The adjuster consists of a solenoid that controls a plunger/valve that variably restricts airflow. The electronic signal sent to the idle speed adjuster determines how much (or little) the plunger constricts airflow. The ECU can control the amount of air that bypasses the throttle when the throttle is fully closed, thereby controlling the engine's idle RPM.

The idle speed adjuster was developed to last the life of the vehicle, but we have seen a substantial amount of failure as the vehicles age. Before you replace the idle speed sensor you should check all of the hoses and connections to check for leaks first.

The idle speed adjuster is located under the intake manifold (red arrow) and cannot be replaced with the manifold on.
Figure 1

The idle speed adjuster is located under the intake manifold (red arrow) and cannot be replaced with the manifold on.

Before you remove the intake manifold you will have to loosen and remove the two hoses from the idle speed adjuster to the manifold (red arrows).
Figure 2

Before you remove the intake manifold you will have to loosen and remove the two hoses from the idle speed adjuster to the manifold (red arrows).

Remove the intake manifold (red arrow); please see our article on intake manifold removal for additional assistance.
Figure 3

Remove the intake manifold (red arrow); please see our article on intake manifold removal for additional assistance. With the manifold off you can see the idle speed adjuster (yellow arrow).

Use a 6mm Allen.
Figure 4

Use a 6mm Allen. Making sure it is properly seated, remove the single mounting bolt holding the ISA in place (red arrow). Note the hoses that attach to the intake manifold (yellow arrows).

Disconnect the vacuum hose from the idle speed adjuster to the brake boosters and vacuum canister (red arrow).
Figure 5

Disconnect the vacuum hose from the idle speed adjuster to the brake boosters and vacuum canister (red arrow). You can see in this photo that the hose to the intercooler to throttle body intake tube (yellow arrow) has already been disconnected.

Label and remove the electrical connection (red arrow).
Figure 6

Label and remove the electrical connection (red arrow). Use care when removing the connection, as they get fragile over the years.

You can now remove the idle speed adjuster (blue arrow) and the accompanying hoses.
Figure 7

You can now remove the idle speed adjuster (blue arrow) and the accompanying hoses. The red arrow hose goes to the intake throttle body tube, the yellow arrow goes to the brake booster/vacuum canister hose and the green arrows go to the intake manifold. Installation is the reverse of removal.


Bookmark and Share

  Search our site:    

View Cart & CheckOut | Project List | Order Status |  Help    

 

[Home] [Customer Service] [Shopping Cart] [Project/Wish List]
  [Privacy Statement]  [Contact Us] [About Us] [Shipping] [Careers]

Copyright © Pelican Parts Inc. -    DMCA Registered Agent Contact Page

Page last updated: Mon 12/5/2016 02:48:26 AM