Could it still be a Vacuum Leak?

[M3Fan]

87 325e.

Symptoms: Cold idle is great. Dead steady at 700RPM. Warm idle sometimes fluctuates/wanders about 200 RPM up and down in a consistent rhythm. This fluctuation stays perfectly consistent in rhythm and 200 rpm scope with no load on the engine if I rev it up to just about any RPM. So if I hold the gas pedal to a 3000RPM, it'll wander there from 2800 to 3000 back and fourth consistently.

It does not always do this, but it's fairly consistent. What have I tried? I have inspected all vacuum hoses. They look pretty good. I have replaced my valve cover gasket and rocker plugs. I have replaced the coil, wires, plugs, cap, rotor, timing belt. I have adjusted the valves. I have replaced the air filter, and cleaned out the throttle butterfly and IAC valve with TB cleaner. Still, this problem creeps up every once and a while. Very weird.

[jlevie]

If the ICV is clean enough that the vane moves freely, it could be bad or the Idle Control Module could be bad.

[iX-treame]

Also check the vacuum lines running to and from the ICV

[M3Fan]

Since the symptoms are also present at any RPM, wouldn't that take the idle circuit out of the equation?

[jlevie]

It should, but if the TPS is bad (shorted idle switch) or the ICM is bad, the ICV could still be a player.

[Cravo]

My m42 has the same symptoms... replaced the ICV, replaced/checked all vac hoses, replaced the TPS and still does it... any suggestions?