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I am pulling codes for my engine indicating a faulty idle control valve. The vehicle at idle seems to hunt jumping between about 800rpm and 1100rpm. It happens maybe every 20 seconds.

If I accelerate moderately to about 2800rpm or over, and suddenly let off the throttle I will get a backfire out both banks and exhausts.

Engine is a V8 BMW M62.

If so can I clean my ICV or does it require replacement?

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2 Answers

The ICV (Idle Control Valve) can be cleaned once removed.

But, it should *not* cause the vehicle to backfire. It sounds like you're dealing with a large vacuum leak. Here are some things that you should have a look at.

After checking for any obvious vacuum leaks around the top of the motor, the Vanos & Crank Case Ventilation System should be next on the list. Make sure to check for leaks at the CCV on the rear of the intake manifold (requires removal of the intake manifold if you need to replace it). Also, the gasket behind the Throttle Body. Below I've added diagrams of the systems and their associated hoses.

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Shown here is the Vanos to Crank Case Ventilation. The CCV located on the back of the intake manifold is located behind #7 (it is not numbered in this diagram). Number 5 is located underneath the Intake Maniforld.


vanosccv

This pipe is aluminum and has internal valves to allow forced air into the cylinder heads


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Diagram of the Air Pump and it's associated hoses.

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Try just spraying Seafoam through it with the vehicle running - you don't even have to take it off. That usually fixes it. If not, you could try taking it off and cleaning it thoroughly, but if the Seafoam didn't solve your problem I think there's a good chance something is wrong with it beyond just being dirty, so you might end up having to replace it.

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