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Intake Air Ducts Replacement
 
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Pelican Technical Article:

Intake Air Ducts Replacement

Nick Czerula

Time:

2 hours2 hrs

Tab:

$50

Talent:

***

Tools:

Set of sockets (10mm), wrenches, flathead screwdrivers, 6mm nut driver

Applicable Models:

BMW Z3 (1996-02)

Parts Required:

Intake air ducts, hose clamps

Hot Tip:

Work with a cool engine.

Performance Gain:

Car will run well

Complementary Modification:

Change engine air filter

The digital motor electronics (DME) engine management system in BMW Z3 vehicles receives input signals from a variety of sensors in order to meter fuel and regulate ignition timing. The most important sensors are as follows:

  • Mass air flow (MAF) sensor ahead of the air filter housing detects the mass and temperature of air entering the intake.
  • Engine coolant temperature (ECT) sensor detects coolant temperature at the cylinder head.
  • Crankshaft position (CKP) sensor detects crankshaft TDC position.
  • Camshaft position (CMP) sensor(s) detect cylinder firing position as well as camshaft timing advance or retard.
  • Engine knock sensor(s) detect preignition or detonation.
  • Oxygen sensors detect oxygen content (and therefore engine combustion efficiency) in the exhaust stream.
  • Accelerator pedal sensor detects driver input for power and acceleration.
  • Radiator outlet hose coolant temperature sensor detects the temperature of coolant leaving the bottom of the radiator.

The mass air flow (MAF) sensor is suspended in the engine intake air stream before air enters the air filter housing. The sensor's element (a thin film of metal, the so-called hot-film sensor) is heated electrically. The ECM monitors its temperature. Fluctuation in the amount of current needed to maintain a steady temperature in the film indicates fluctuations in the mass of air flowing through the intake. The ECM uses this information to calculate the volume of fuel to inject.

The MAF sensor is attached to the air intake using rubber ducts. When an intake air duct cracks or tears, extra air may be routed around the MAF sensor. Therefore the MAF sensor signal becomes unreliable. Air entering through the tear in the duct is unmetered. The engine management system cannot calculate fuel injection based on it. Engine drivability may suffer. Or you may have a rough idle, or hard start or a malfunction indicated light (MIL or Check Engine light) that is ON with fuel trim faults. 

Be sure to inspect your intake air ducts each time you service your vehicle. This will uncover problems you can prevent by replacing dry rotted or cracked air ducts.

When replacing your intake air ducts, replace them in pairs. If you are removing both and only one is cracked, it still makes sense to replace both.

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 have two intake air boots to worry about.
Figure 1

Models with 4-cylinder engine: 4-cylinder models have two intake air boots to worry about. The front boot (green arrow) tends to wear in more obvious spots, (inside the bellows) while the rear boot (yellow arrow) cracks in not so visible spots. I suggest replacing both as a set.

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

Models with 4-cylinder engine: 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

Models with 4-cylinder engine: 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

Models with 4-cylinder engine: 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

Models with 4-cylinder engine: 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

Models with 4-cylinder engine: 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

Models with 4-cylinder engine: Now, you can loosen the front boot hose clamp (green arrow) and remove it from the intermediate throttle.

Then, loosen both hose clamps at the rear boot (green arrows).
Figure 8

Models with 4-cylinder engine: Then, loosen both hose clamps at the rear boot (green arrows). Once loose, pull the intermediate throttle (yellow arrow) out of the boot. You can leave the cable connected, just lay it aside. Next, pull the boot off the main throttle housing to remove.

This photo shows a crack in the rear boot (green arrow).
Figure 9

Models with 4-cylinder engine: This photo shows a crack in the rear boot (green arrow). Normally not visible unless you remove the boot to inspect it. This is why I suggest replacing both at the same time.

When installing the new boots, be sure all the molded arrows align (green arrows) on the boots.
Figure 10

Models with 4-cylinder engine: When installing the new boots, be sure all the molded arrows align (green arrows) on the boots. This will ensure proper alignment. Reverse the remainder of the steps for installing your new boots.

Models with 6-cylinder engine:
This photo shows intake air duct damage.
Figure 11

Models with 6-cylinder engine: This photo shows intake air duct damage. The duct has dry rotted and cracked (green arrow). The vehicle duct was replaced and had fault codes for fuel trim bank 1 and bank 2, Lean.

Remove the air filter housing assembly.
Figure 12

Models with 6-cylinder engine: 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 13

Models with 6-cylinder engine: 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 14

Models with 6-cylinder engine: 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 15

Models with 6-cylinder engine: Working at intake resonance valve, remove two T40 Torx fasteners. (green arrows)

Remove resonance valve from intake manifold.
Figure 16

Models with 6-cylinder engine: Remove resonance valve from intake manifold.

Next, remove the intake air ducts from throttle housing.
Figure 17

Models with 6-cylinder engine: 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.


With duct removed from vehicle, mark orientation using paint marker. This will help get the ducts back into correct position when reinstalling. Loosen hose clamps and separate ducts. Install new ducts in the same position as old, using your mark. Then reassemble intake air ducts and air filter housing in reverse order of removal. Check that ducts, hoses and electrical harnesses are routed as they were before and check that air ducts are properly sealed.

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Comments and Suggestions:
vaiarii Comments: HI ! I have a bmw 316i 2000 year and I would like to order two intakkes air boots for my 4-cylinder engine.
So do you ship to French POlynesia ! can i hva the price of the part please !

Sincerely,

Vaiarii
August 12, 2014
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- Nick at Pelican Parts
 

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