BMW E46 Rough Idle Repair – 3 Series M54 Engine

BMW E46 rough idle

BMW E46 Rough Idle Repair Time – 2 Hours

BMW E46 Rough Idle Repair

The BMW Repair Guide used this 2003 325ci for the following article. To see other repairs on our site using this actual car, please click on the image below!

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.

Parts, Tools and Supplies


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

Parts and Supplies
BMW E46 DISA valve
BMW E46 idle control valve grommet
BMW E46 idle control valve

        1. Remove the right side engine cover using a pick and a 10mm nut driver as shown below. bmw fuel pressure test
        2. Remove the cabin air filter cover by unsecuring the 3 twist screws that mount it to the filter housing.
          bmw fuel pressure test BMW E46 blower motor
        3. Using a torx T30 bit remove the three screws securing the filter housing to the fire wall. Remove the filter housing from the fuel pressure test BMW E46 blower motor
        4. 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 e46 blower motorbmw e46 blower motor
        5. 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.BMW E46 intake manifold
        6. Disconnect the Mass Air Flow (MAF) sensor.BMW E46 intake manifold

          One of the quickest ways to get yourself in trouble on a DIY repair is to forget to reconnect wiring harnesses and hose connections. It is a very common mistake that can turn a 30 minute repair into hours of frustration! To insure this doesn’t happen on your next repair, mark all important connections with a bright colored tape so you don’t miss them during reassembly. Be sure to write down where the connection goes as well.

          bmw e46 intake manifold

        7. Using a flat blade screwdriver, loosen the hose clamp connecting the air intake boot to the air box.BMW E46 intake manifold
        8. Remove the air box from the engine compartment.BMW E46 intake manifold
        9. Remove the vacuum line from the intake boot.BMW E46 intake manifold
        10. Remove the DISA valve electrical connector. The release spring is on the back side of the connector.BMW E46 intake manifold
        11. Using a T40 torx bit, remove the two screws anchoring the DISA valve to the intake manifold. Grasp the DISA valve and carefully remove.BMW E46 intake manifold BMW E46 intake manifold
        12. 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).BMW E46 intake manifold
        13. 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.BMW E46 intake manifolBMW E46 intake manifol
        14. Disconnect electrical connection to the throttle body. You may need the help of a flat blade screwdriver to get it loose.BMW E46 intake manifoldBMW E46 intake manifold
        15. 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.BMW E46 intake manifold
        16. Next move down the wiring harness and remove the 10mm bolt using a nut driver or socket and wrench.BMW E46 intake manifold
        17. Next, the bottom throttle body mounting bolt must be removed. Use a 10mm socket wrench with extension.BMW E46 intake manifold
        18. Finally, remove the 10mm bolt anchoring the engine wiring harness to the idle control valve.BMW E46 intake manifold
        19. Grasp the idle control valve and pull it out of the intake manifold.BMW E46 intake manifoldBMW E46 intake manifold
        20. Locate the idle air valve rubber grommet and remove with a pair of long reach needle nose pliers.BMW E46 rough idle BMW E46 rough idle
        21. 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 idleBMW E46 rough idle


        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.

        Repair finished
        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.