How do I test the Idle Control Unit

[Vanagonjohn]

I took my baby to a local vw shop and he said that my Idle Control Unit was bad and the why my van rev's up then down then up then down when in park and neutral.

[kshbaja]

Easiest test is to disconnect it and see if behavior changes.
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1986 Westfalia

[Colonel_Brown]

Swap in a working one and see if your idle hunting disappears, otherwise the only other way I've heard is "it should hum" when at idle.

I had this issue myself... It was caused by a number of unrelated problems that in turn made my idle too high >1100RPM. According to the Bentley when the idle gets too high the ECU will cut off fuel to the injectors ergo engine RPMs drop --> then ECU gives the all clear and FI restarts --> RPMs return to a high idle --> ECU shuts down fuel pump --> RPMs drop --> etc. etc. etc.

Long story short, is your idle too high?
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'84 Vanagon GL (1.9L) - "Colonel Brown"

[Vanagonjohn]

Thank for the input so fast. I will disconnect it and see what happens. My idle is right on I think where should it be.

[kshbaja]

You might have trouble with a cold start with it disconnected but once it warms up it should be fine. I had this same issue.
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1986 Westfalia

[Vanagonjohn]

So I played with my idle and now the problem is gone I ran for the last 10 min. And it didn't happen anymore. Thanks to everyone that posted.

[kshbaja]

You might want to consider resetting your base idle and timing based on the Bentley procedure....or just let a sleeping dog lie! Often time folks will attempt to fix what is actually a timing or MAF problem by adjusting the idle. Without resetting everything, the 3 or 4 variables involved are never correct.
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1986 Westfalia