Porsche Parts Catalog Porsche Accessories Catalog Porsche Technical Articles Porsche Tech Forums
 
  Search our site:    
View Recent Cars  |   Cart  | Project List | Order Status | Help    
 >  >
Air Flow Sensor Repair and Replacement
 
Bookmark and Share

Pelican Technical Article:

Air Flow Sensor Repair and Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$850

Talent:

**

Tools:

17mm wrench, 5mm Allen, 10mm wrench, razor blade, flathead screwdriver

Applicable Models:

Porsche 944 Turbo (1986-89)

Parts Required:

New air flow meter

Hot Tip:

Work gently with the internals of the sensor

Performance Gain:

Proper running motor

Complementary Modification:

Change air filter

The air flow meter or air-flow sensor on the Porsche 944 uses a barn door type sensor that opens and closes. The movement of the barn door moves a wiper arm across the conducting strip of a variable potentiometer. This strip has an electrical current running through it from the DME computer. As the barn door moves, it moves the arm on the sensor strip. This process changes the voltage sent to the DME.

While the air flow sensor can fail over time, it is a very expensive part. That said, it is a good idea to check it for the most common and simplest of repairs before just replacing it. The most common fault is that the wiper arm tends to wear a groove in the conducting strip over the years. This can cause stumbling as it moves and improper signals being sent to the DME.

While you can work on the AFS or AFM while it is in the vehicle, it is a very sensitive part. So it is best to remove it and take it to your bench. If you are going to be replacing it, it must be removed along with the air box.

Begin by opening the hood and having a look at the engine.
Figure 1

Begin by opening the hood and having a look at the engine. The air box is located in front of the engine (red arrow) with a cold air intake running to the left front fender area (yellow arrow). The air-flow sensor is under the lid and intake tube (green arrow).

Remove the two flathead screws connecting the air box to the intake tube (red arrows).
Figure 2

Remove the two flathead screws connecting the air box to the intake tube (red arrows).

Remove the tube by lifting it up and pulling it out from the grommet it sits in within the inner fender (red arrow).
Figure 3

Remove the tube by lifting it up and pulling it out from the grommet it sits in within the inner fender (red arrow).

Remove the three fasteners securing the air box lid to the base (red arrows).
Figure 4

Remove the three fasteners securing the air box lid to the base (red arrows).

Disconnect the line running to the turbo pipe with a 17mm wrench.
Figure 5

Disconnect the line running to the turbo pipe with a 17mm wrench. Note that there are two washers (red arrows) that need to be replaced if you remove the line.

Disconnect the clamp over the pipe by reaching down and unclipping it.
Figure 6

Disconnect the clamp over the pipe by reaching down and unclipping it. Then remove the lid. Next use a flathead screwdriver and loosen the hose clamps on both ends of the pipe (red arrows).

Remove the pipe from the engine (red arrow).
Figure 7

Remove the pipe from the engine (red arrow).

Remove the three fasteners on the air box mounts (red arrows).
Figure 8

Remove the three fasteners on the air box mounts (red arrows).

Disconnect the wiring for the air-flow sensor.
Figure 9

Disconnect the wiring for the air-flow sensor. Use care when working with the connection; make sure the wire is released before removing it (red arrow). These connectors get very brittle with age. You do not want to damage it.

Use a flathead screwdriver and loosen the clamp holding the air-flow sensor to the tube (red arrow).
Figure 10

Use a flathead screwdriver and loosen the clamp holding the air-flow sensor to the tube (red arrow).

Slip the air box and air-flow sensor back out from under the intake tube and up and out from the motor (red arrow).
Figure 11

Slip the air box and air-flow sensor back out from under the intake tube and up and out from the motor (red arrow).

To remove the air-flow sensor from the air box, remove the three 10mm bolts from the top of the air box (red arrows).
Figure 12

To remove the air-flow sensor from the air box, remove the three 10mm bolts from the top of the air box (red arrows).

Turn the air box over and remove the single 10mm bolt from the bottom (red arrow).
Figure 13

Turn the air box over and remove the single 10mm bolt from the bottom (red arrow).

Separate the air box (yellow arrow) from the AFS (red arrow).
Figure 14

Separate the air box (yellow arrow) from the AFS (red arrow). Make sure to replace the gasket between them (green arrow).

Looking into the air-flow sensor, you can see the barn door that swings open and closed as air flows through (red arrow).
Figure 15

Looking into the air-flow sensor, you can see the barn door that swings open and closed as air flows through (red arrow).

The plastic lid on the housing is held in place by a bead of silicon sealant.
Figure 16

The plastic lid on the housing is held in place by a bead of silicon sealant. Use a razor blade and carefully cut the sealant away (red arrow).

With all the sealant removed, carefully pry the lid up and off.
Figure 17

With all the sealant removed, carefully pry the lid up and off. Remember, the lid has been on a long time, so take your time removing it and do not break it! The lid is not sold separately. You cannot have dirt and debris getting into the workings of the sensor.

Before replacing the unit, check the wiper arm (yellow arrow) and the conducting strip (red arrow) for grooves and build up.
Figure 18

Before replacing the unit, check the wiper arm (yellow arrow) and the conducting strip (red arrow) for grooves and build up. You can clean the conducting strip with a pencil eraser, but make sure to use a very light touch. You can clean the wiper arm without disassembling it by slipping a piece of paper under it and then using a small piece of Emory cloth to clean the contact point. 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 02:46:48 AM