Violently cyclic idle - MC engine

Phil Payne quattro at
Mon Sep 13 08:48:44 EDT 2004

> Basically the idle problems occur due to ISV, Throttle Body screw(o-ring), WOT/Idle Switch
wiring or switch adjustment, air leaks and lastly and leastly the ISV Relay itself as I have
not seen one go bad.

Well, we got a new one - none of the above apply - though I haven't changed the ISV controller

I have four ISVs in stock.  My usual method of testing is to apply a PP9 battery across the
while blowing through - no leakage without voltage, instant leakage with.  With the PP9, the
plunger moves about 2mm.

I've also tested the return spring tension - all the same.

I plugged the throttle body screw with Blu-Tack.  You can usually hear a throttle body leak,
no matter where it is.  Nothing.

The WoT switch was replaced with a functional Type 2 about six months back - it clicks
positively at idle.  The whole throttle body was dismounted, degreased and relubed at the

No air leaks - pulling the dipstick causes an instant stall.  The crankcase breather hose is
collapsed - waiting for a new one.  But it's been like that for a while.

  Phil Payne
  +44 7785 302 803

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