The 1998 BMW M44 engine is generally reliable, but like all motors, its components will develop issues over time. Common problems on ageing M44 engines are hesitation and rough idle. While there are many faults that can cause these symptoms, a likely culprit is the ICV or idle control valve. Cleaning the ICV to remove built-up deposits is simple and should be a part of every M44 owner's maintenance plan.
- Skill level:
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Things you need
- Flat head screwdriver
- 11mm wrench
- Can of throttle body cleaner
- Plastic bucket
Park the car on level ground and turn the engine off. Allow the engine to cool down if it is hot.
Open the bonnet. Loosen the screws on the hose clamps at each end of intake tube by turning them counterclockwise with the screwdriver. Remove the intake tube.
Remove the four 11mm bolts securing the throttle body by turning them counterclockwise with the 11mm wrench. Push the throttle body to the side, but leave it connected to the engine by its hoses.
Remove the five 11mm bolts securing the upper intake manifold by turning them counterclockwise with the 11mm wrench. Remove the intake manifold. You now have access to the ICV.
Remove the two screws securing the rubber strap on top of the ICV. Disconnect the electrical wire from the ICV by squeezing the clips and pulling the connection directly away from valve. Pull the rubber hoses on each end of the ICV free of their engine-side connections, but leave them attached to the ICV.
Remove the idle control valve from the car, along with the rubber hoses. Pull the rubber hoses free of the ICV.
Hold the ICV over a bucket and spray it generously with throttle body cleaner inside and out. Be sure to spray into the openings at both ends of the valve to reach the internal parts. Drain excess cleaner into the bucket.
Spray each of the rubber hoses inside and out with throttle body cleaner.
Allow the idle control valve to dry for an hour before reinstalling it.
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