Violently cyclic idle - MC engine

[Phil Payne]

> >Occasionally the idle goes into a _VIOLENT_ cycle - quite agressively cycling between ca.
1050
> >rpm and 1500 rpm.  Cycle is around 1Hz.
> >
> >Only code is 2312 (temperature sender) - I've tried three now and still get the code, but
the
> >harness has been butchered at some time so I need to restore it.  I plan on diving in
> >tomorrow.

> What's the system pressure and control pressure doing during these
> cycles.

Don't know - the meter is going on in a few hours.

> The MC controls idle speed via air bypass only or does it use the
> ignition?

Air bypass only - I have a lead made up to measure current trhough it and I'll try that.  It
was set up for 430mA only about a month ago.

> Check the WOT and throttle idle switch- maybe the idle switch and/or WOT is
> intermittently shorting causing false WOT/non-idle conditions.

Nope.  Swapped the WoT switch.  Doesn't eliminate the harness, though.

> Also check the warm up regulator - if that was wacky ( power, bi-met strip issue)
> the control pressure could be cycling.

Not at 1Hz.  BRUM-BRUM-BRUM-BRUM - like I was hitting the pedal once a second.

-- 
  Phil Payne
  http://www.isham-research.com
  +44 7785 302 803