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Throttle Housing Replacement
 
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Pelican Technical Article:

Throttle Housing Replacement

Nick Czerula

Time:

3 hours3 hrs

Tab:

$300 to $700

Tools:

Set of sockets T40 Torx socket, flathead, Phillips screwdrivers

Applicable Models:

BMW Z3 Coupe/Conv (1996-02)

Parts Required:

Throttle housing, throttle housing gasket, TPS, IACV, gaskets, O-rings

Hot Tip:

Work with a cool engine.

Performance Gain:

Car will run well.

Complementary Modification:

Inspect intake air ducts and replace if necessary. Replace air filter.

The digital motor electronics (DME) engine management system in BMW Z3 vehicles may be equipped with one of two different throttle systems:

  • 4-cylinder engine and 6-cylinder M52 engines (1990--2000 models) are equipped with a conventional throttle cable connecting the accelerator pedal to the throttle housing.
  • M52 TU and M54 engine (2001--2002 models) are equipped with an electronic throttle (drive-by-wire). There is no throttle cable. Instead, potentiometers in the accelerator pedal module (PWG) communicate pedal position directly to the engine control module (ECM). Two separate signals, one signaling pedal position and the other indicating rate of pedal movement, communicate driver demand on the system. Based on pedal position and movement, the ECM communicates throttle opening to the throttle housing at the intake manifold. 

A faulty throttle housing can cause a number of problems for your BMW Z3, from a check engine light to a rough or surging idle. Before you condemn your throttle housing, be sure to inspect all the intake air ducts. They should be well-sealed and free from cracks or tears. Check the function of your Z3 crankcase breather valve and inspect all breather hoses. If a breather hose cracks or fails, the air leak can cause a rough idle or engine stalling. On electronic throttle vehicles, inspect the throttle housing electrical connector condition; the pins have a tendency to lose tension. The best way to check pin tension is with a pin fit kit. However, as this may not be available to you, you can visually inspect the pins and see if they are spread open or bent. 

I'll also go over some notes on replacing the idle air control valve and throttle position sensor on 4-cylinder models.

To avoid marring the paint and trim, work with a plastic prying tool or wrap a screwdriver tip with masking tape before prying out body or interior items.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches. 

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability. 

Vehicle models change and evolve, as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Models with 4-cylinder engine:
4-cylinder models can have two throttle housings.
Figure 1

4-cylinder models can have two throttle housings. One for the cruise control (yellow arrow) also referred to as the intermediate throttle, and the primary throttle housing (green arrow). Only vehicles with cruise control will have the intermediate throttle housing. If you donÂÂÂ't have cruise, you will have a single intake air boot and a single throttle housing.

Using a flathead screwdriver, loosen the secondary air pump inlet hose clamp.
Figure 2

Using a flathead screwdriver, loosen the secondary air pump inlet hose clamp. (green arrow)

Then remove the secondary air inlet hose from the air filter housing by pulling it straight off.
Figure 3

Then remove the secondary air inlet hose from the air filter housing by pulling it straight off. (green arrow)

Next, you will unclip the three air filter housing retaining clips.
Figure 4

Next, you will unclip the three air filter housing retaining clips. (green arrows). One of the clips was hidden beneath the secondary air inlet hose. You will have to reach in behind air filter housing to access it.

Disconnect the intake air sensor electrical connector by pressing the wire release tab and pulling the connector straight off.
Figure 5

Disconnect the intake air sensor electrical connector by pressing the wire release tab and pulling the connector straight off.

Working at the air flow meter, twist electrical connector counterclockwise to disconnect.
Figure 6

Working at the air flow meter, twist electrical connector counterclockwise to disconnect. (green arrow). Then loosen the air flow meter hose clamp (yellow arrow). Once loose, remove the air filter housing from the engine compartment.

Now, you can loosen the front boot hose clamp (green arrow) and remove it from the intermediate throttle.
Figure 7

Now, you can loosen the front boot hose clamp (green arrow) and remove it from the intermediate throttle.

Disconnect the intermediate throttle housing position sensor electrical connector by pressing the wire retainer and pulling off sensor.
Figure 8

Disconnect the intermediate throttle housing position sensor electrical connector by pressing the wire retainer and pulling off sensor.

Then, loosen the hose clamp at the rear boot (green arrow).
Figure 9

Then, loosen the hose clamp at the rear boot (green arrow). Once loose, pull the intermediate throttle out of the boot.

With the intermediate throttle removed, you now have to remove the throttle cable from the housing.
Figure 10

With the intermediate throttle removed, you now have to remove the throttle cable from the housing. Start by closing the throttle by rotating the throttle lever to 100%, then remove the cable end (green arrow) from the lever by pulling it straight out. Once the cable end is removed, remove the cable from the bracket by releasing the two retaining tabs and pulling it straight out. You can see this vehicle has had the cable tabs broken (yellow arrow) and someone used dum dum to secure the cable in. This cable will have to be replaced because the retaining tabs are broken.

Loosen the clamp at the throttle housing air boot (green arrow), then remove the air boot from the throttle housing.
Figure 11

Loosen the clamp at the throttle housing air boot (green arrow), then remove the air boot from the throttle housing. You will have to disconnect the large vent hose that goes to the side of the air boot.

Next you have to remove the vacuum hoses (green arrows) at the throttle housing.
Figure 12

Next you have to remove the vacuum hoses (green arrows) at the throttle housing. Start by pulling off the smaller hose.

Then pull the large hose off.
Figure 13

Then pull the large hose off. If it will not come off easily, use a flathead screwdriver to lever it off. Be careful not to damage the hose while levering it off. Once the vacuum hoses are removed, disconnect the electrical connectors by pressing the wire release tab (green arrows) and pulling it straight off.

Working at the top of the throttle housing.
Figure 14

Working at the top of the throttle housing. Loosen the flathead screw (green arrow) for the cable cover.

Once the screw is loose, lift the cover up and remove from throttle housing.
Figure 15

Once the screw is loose, lift the cover up and remove from throttle housing.

Now that you have access to the throttle cables, use a pair of needle nose pliers and release the throttle cable ends (green arrows) from the throttle housing lever.
Figure 16

Now that you have access to the throttle cables, use a pair of needle nose pliers and release the throttle cable ends (green arrows) from the throttle housing lever. Squeeze the plastic ends together gently, to release from the lever.

Then remove the cable ends from the lever through the openings (green arrows) provided.
Figure 17

Then remove the cable ends from the lever through the openings (green arrows) provided.

Next remove the four 10mm throttle housing nuts (green arrows).
Figure 18

Next remove the four 10mm throttle housing nuts (green arrows).

With the nuts removed, slide the throttle housing off the mounting studs to remove.
Figure 19

With the nuts removed, slide the throttle housing off the mounting studs to remove.

Lay the throttle housing on its side and remove the three T27 Torx fasteners (green arrows) from the cable bracket.
Figure 20

Lay the throttle housing on its side and remove the three T27 Torx fasteners (green arrows) from the cable bracket. Then remove the cable bracket from the throttle housing.

When installing the new throttle housing, be sure to replace the profile gasket (green arrow).
Figure 21

When installing the new throttle housing, be sure to replace the profile gasket (green arrow). Install throttle cable bracket to housing. Then install housing to intake manifold. Next, snap the cable ends into the lever, be sure they are properly engaged.

When installing the air boots, be sure all the molded arrows align (green arrows) on the boots.
Figure 22

When installing the air boots, be sure all the molded arrows align (green arrows) on the boots. This will ensure proper alignment. Reverse remaining steps for reinstallation.

A few notes about the throttle position sensor (TPS) (green arrow) and the idle air control valve (IACV) (yellow arrow) on the throttle housing.
Figure 23

A few notes about the throttle position sensor (TPS) (green arrow) and the idle air control valve (IACV) (yellow arrow) on the throttle housing. To replace the TPS, simply remove the two Phillips head screws, remove the sensor and install the new one. Be sure to replace the sealing O-ring. The sensor does not need to be adjusted or calibrated, it is self-adjusting. The IACV has been known to cause many idle issues, stalling and noise. If you have a no start condition, but slightly opening the throttle allows the engine to start, the problem might be your IACV is stuck closed. If you have a whistle at idle, this could be from the IACV valve also. Replace the valve for both problems. To do so, remove the two T27 Torx fasteners, remove the valve then install the new valve with a new gasket. 

Model with 6-cylinder engine:

Disconnect negative (-) battery cable. See our tech article on Battery connection notes.
Remove the air filter housing assembly.
Figure 24

Remove the air filter housing assembly. Remove the 10mm fastener (green arrow), then disconnect air flow meter electrical connector (yellow arrow). Now loosen the air flow meter clamp (red arrow) and lift the air filter housing out of the engine compartment.

Working at the top of the intake air duct, pull vacuum hose connector out of duct.
Figure 25

Working at the top of the intake air duct, pull vacuum hose connector out of duct.

Working at intake resonance valve, disconnect electrical connector (yellow arrow) by pressing wire release tab and pulling straight off.
Figure 26

Working at intake resonance valve, disconnect electrical connector (yellow arrow) by pressing wire release tab and pulling straight off.

Working at intake resonance valve, remove two T40 Torx fasteners.
Figure 27

Working at intake resonance valve, remove two T40 Torx fasteners. (green arrows)

Remove resonance valve from intake manifold.
Figure 28

Remove resonance valve from intake manifold.

Next, remove the intake air ducts from throttle housing.
Figure 29

Next, remove the intake air ducts from throttle housing. There are two hose clamps to loosen, one at idle valve (yellow arrow), the other at throttle housing (green arrow). Reach below duct with a 6mm nut driver, (near engine mount) and loosen clamps from below. Once loose, remove duct from engine.

Follow the engine oil dipstick tube down toward engine mount.
Figure 30

Follow the engine oil dipstick tube down toward engine mount. Remove dipstick tube using a 13mm fastener (green arrow), then rotate dipstick tube away from throttle housing.

Working next to throttle housing, remove three 10mm nuts and bolt from wiring harness junction.
Figure 31

Working next to throttle housing, remove three 10mm nuts and bolt from wiring harness junction. (green arrows)

Next, disconnect idle air valve electrical connector.
Figure 32

Next, disconnect idle air valve electrical connector. (green arrow)

Pull the wiring harness junction from your intake manifold and lay aside.
Figure 33

Pull the wiring harness junction from your intake manifold and lay aside.

On early models with M52 engine (MS 42.
Figure 34

On early models with M52 engine (MS 42.0). Disconnect the throttle housing cable by pulling up and out of rubber retainer (green arrow). Vehicles with MS43 engine software do not have a throttle cable.

Remove the idle air valve T40 Torx fasteners.
Figure 35

Remove the idle air valve T40 Torx fasteners. (green arrows) On early models with M52 engine (MS 42.0): Remove throttle cable mounting bracket from engine.

Then pull idle valve out of the intake manifold and remove.
Figure 36

Then pull idle valve out of the intake manifold and remove. Depending on how long the valve has been in the vehicle, it may be stuck to the rubber hose it mounts in. If this is the case, gently work the valve side to side as you pull it out.

On early models with M52 engine (MS 42.
Figure 37

On early models with M52 engine (MS 42.0): Reach down next to the throttle housing and fully open the throttle using the plastic lug on side as shown (yellow arrow). Disconnect the throttle cable by pulling ball end down and out of the throttle lever (green arrow).

On early models with M52 engine (MS 42.
Figure 38

On early models with M52 engine (MS 42.0): Disconnect the throttle housing electrical connector (green arrow) by rotating counterclockwise until it pulls away from the throttle housing.

Next, disconnect the throttle housing electrical connector.
Figure 39

Next, disconnect the throttle housing electrical connector. (green arrow) This photo shows a late model MS43 engine software. To disconnect, squeeze release tab and pull off throttle housing.

Remove the throttle housing fasteners.
Figure 40

Remove the throttle housing fasteners. (yellow arrows) Then remove the throttle housing from your engine. To install throttle housing reverse removal directions. Use the following notes:

Remember to replace throttle housing gasket.
Figure 41

Remember to replace throttle housing gasket. (green arrow)

On early models with M52 engine (MS 42.
Figure 42

On early models with M52 engine (MS 42.0): Adjust throttle cable by twisting knurled section (yellow arrow) on vehicles with MS 42.0. Late models MS43 engine software: Perform throttle adaptation as described below.

Be sure that all electrical connectors are properly seated.
Figure 43

Be sure that all electrical connectors are properly seated. Listen for an audible click when connecting. On early models with M52 engine (MS 42.0), align white arrows on electrical connector and throttle housing when installing. (green arrows) Adjusting throttle cable MS 42.0 If you havenÂÂÂ't replaced the throttle cable and only replaced the throttle housing, you donÂÂÂ't have to adjust the cable. I have included the procedure in the case you need it. The following steps highlight basic throttle cable adjustment: Adjust throttle cable so that at idle (accelerator pedal at rest) the cable has a small amount of play where cable attaches to throttle lever. The maximum amount of play you want to achieve is 3mm (0.125in).

To adjust, rotate adjuster (green arrow) located at end of throttle cable housing.
Figure 44

To adjust, rotate adjuster (green arrow) located at end of throttle cable housing.

You also have to adjust cable at full throttle position.
Figure 45

You also have to adjust cable at full throttle position. You will need a scan tool that reads engine data stream, specifically throttle angle (green arrow). On vehicles with manual transmission: Turn ignition key to ON position, press accelerator pedal to floor (full stop). Throttle angle should read 80° - 84°. On vehicles with automatic transmission: Turn ignition key to ON position, press accelerator pedal until pedal reaches kickdown stop. Throttle angle should read 76° - 80°. On vehicles with automatic transmission: Turn ignition key to ON position, press accelerator pedal past pressure point of kickdown switch. Throttle angle should read 84° - 88°. On vehicles with automatic transmission: Turn ignition key to ON position, press accelerator pedal to floor (full stop). Throttle angle should read 100° or 100%. Throttle housing adaptation MS 43 Turn ignition key to ON position for 10 seconds, (do not start engine) Next turn ignition key to OFF position for 10 seconds. Start engine

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Page last updated: Wed 12/7/2016 02:07:04 AM