BMW E46 Rough Idle Repair Time – 2 Hours
If your 3 series is showing rpm fluctuations when holding the accelerator at a constant speed, or if the engine rpm in your car repeatedly drops and then recovers when idling, then it may be time for a BMW E46 rough idle repair.
We say it in most articles we write, so excuse us for being redundant. But for many of us our Bimmers are unfortunately getting old. Ok…insert your sad frowny face emoji here.
When Bimmers get over ten years old, its time to face the facts that many engine parts are going to need replacement, especially in the air intake system. The intense heat of the engine compartment, compounded by the age and “wear and tear” of the vehicle, plays havoc on the hoses, boots, gaskets and valves that make up your BMWs air intake system.
A BMW E46 rough idle repair is a fairly simple job that requires replacing your DISA and idle control valves. If you are interested in what the DISA and idle control valves do, please refer to our rough idle repair article for the BMW E60 5 series where we go into a more in depth discussion.
The BMW Repair Guide recommends replacing both valves when performing a BMW E46 rough idle repair. Since both parts have a maximum life span of approximately 100,000 miles, if one is failing most likely the other is ready to go as well. Do yourself a favor and spend the extra money and replace both parts.
10mm nut driver
10mm socket with ratchet and extension
T30 torx bit with extender and ratchet
T40 torx bit with extender and ratchet
Flat blade screwdriver
Long reach needle nose pliers
- Remove the right side engine cover using a pick and a 10mm nut driver as shown below.
- Remove the cabin air filter cover by unsecuring the 3 twist screws that mount it to the filter housing.
- Using a torx T30 bit remove the three screws securing the filter housing to the fire wall. Remove the filter housing from the vehicle.
- Using a T30 torx bit, loosen the two bolts securing the metal bulkhead cover (the bolts are attached to the cover and should not be able to be completely removed). Remove the bulkhead cover from the car.
- The next step in the BMW E46 rough idle repair is to remove the air box from the engine compartment. Use a 10mm nut driver or socket wrench to remove the two air box mounting bolts on the left side (driver’s side) of engine compartment.
- Disconnect the Mass Air Flow (MAF) sensor.
- Using a flat blade screwdriver, loosen the hose clamp connecting the air intake boot to the air box.
- Remove the air box from the engine compartment.
- Remove the vacuum line from the intake boot.
- Remove the DISA valve electrical connector. The release spring is on the back side of the connector.
- Using a T40 torx bit, remove the two screws anchoring the DISA valve to the intake manifold. Grasp the DISA valve and carefully remove.
- Using a flat blade screwdriver, loosen the hose clamp anchoring the top hose of the intake boot to the idle control valve. Pull the top hose off of the idle control valve being careful not to bend or tear it (there is a screw below it we need to get to in the next step).
- Using a flat blade screwdriver, loosen the hose clamp anchoring the intake boot to the throttle body. Pull the intake boot off of the throttle body and remove from vehicle. You will notice from the photo below we damaged our intake boot during removal. This boot had 140,000 miles on it and ripped apart during removal. If this happens to you, order a new boot here.
- Disconnect electrical connection to the throttle body. You may need the help of a flat blade screwdriver to get it loose.
- Now it is time to loosen the engine wiring harness so the idle control valve can be removed from the manifold. Start by removing the top two T40 torx bolts.
- Next move down the wiring harness and remove the 10mm bolt using a nut driver or socket and wrench.
- Next, the bottom throttle body mounting bolt must be removed. Use a 10mm socket wrench with extension.
- Finally, remove the 10mm bolt anchoring the engine wiring harness to the idle control valve.
- Grasp the idle control valve and pull it out of the intake manifold.
- Locate the idle air valve rubber grommet and remove with a pair of long reach needle nose pliers.
- Remove the idle control valve mount by sliding the valve out of the rubber retaining sleeve. Note the position of the valve in the mount during reassembly.
BMW E46 rough idle repair reassembly – simply follow steps 1 through 20 in reverse order. Make sure the idle control valve grommet is correctly seated in the intake manifold so you have a nice tight fit with no leaks.
If you have any questions or comments, please feel free to contact us. And congratulations for Doing It Yourself!
The Repair Difficulty Level displays graphically how challenging the repair is, from easy to advanced. Easy repairs usually require very few tools, have short repair times and do not require jacking and supporting the vehicle. As the difficulty level rises, expect the repair to demand more time, specialized tools, and better understanding of mechanics to complete the job.