75 TS: Misbehavin'..FOUND IT!

[David Masters <david@domain.elided>]

Lars, this is great news.  It just goes to show that the same old problems keep
coming up, and people should KISS when diagnosing problems.

A few questions remain in my mind, so please give me a moment more.
Did you find that the idle ever hunted up and down?
Would the kangarooing only happen when you tried to drive away?
Had you done a continuity test on the TPS?

My feeling was that the idle switch is responsible for the hunting idle 
in conjunction with a slow idle-speed-controller, but that the poor running 
you experienced is due to the rotors having lost their correct resistance 
due to the goo melting on the top of the rotor.  You said that you had 
already soldiered up the wire in the 6 wire connector, so it can't be that,
even though the symptoms are perfect!

Determining why the goo on the rotor melts is a problem for another day, and I have 
concerns about the oil feed to the distributor on the front of the engine. Has 
anyone looked into that area?

When I cleaned my TPS some years back, it was rust that had caused 
my problem, judging by the colour of the discharge.  I had a definite, 
reproducible problem with continuity on the TPS at idle.  After WD40 it
was gone.

Cheers,
david


 Lars said ....
Hello out there!
I'd like to share this recently found knowledge.
This summer I had some problems with the engine,
At idle it worked perfect, but sometimes, when hot weather,
I pressed the gaspedal it acted like kangaroo, with clutch
pressed the rev was oscillating vigoursly. Release the throttle to
idle position and tried again, then the malfunction was gone.
And sometimes, when driving at constant speed, there was just no power
at all,
the enginge became totally cut-off with no response to throttle.
Pressing the clutch and letting the rev decrease to idle speed did it,
after that I
had power as usual.
Very annoying.
I never found it, it became atumn and the symptom dissapeared.

Today, I did some garage-work. Replaced the dist caps, rotors and
ignitioncables.  And I also took the butterfly apart, drained the
cooling fluid so
it could be removed from the intake manifold.  I recalled what David
wrote recently,
about the idle switch. I found that the lid of the switch couldn't be
prised off
without damaging the cover, so I made two small holes in the plasic
cover and sprayed
WD-40 inside. What came out was dark coloured. I'm not sure if it was
some kind of grease
that was supposed to be inside, or just dirt. Lower throttle axis
bearing leaking, letting oil-water mix
from the crankcase vent in?
But, the main point is, that after that operation the engine turned into
a kangaroo again, and I
could clearly hear that the switch one time out of five didn't say
"clic"
So, finally, I've found the cause for this summers misbehaving!
OK, maybe I've destroyed the switch but it was defenitively not good
before.

So, This is the behavour when the idle switch is bad, and
the switch can be failing intermittent and temperature depending.

Soon on the road again ;-)
Lars A
75 TS 1990

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