Re: oil filler-cap effect on idle--how much?

[Phil and Judy Rose <pjrose@servtech.com>]

Phil payne wrote:

>>In message <v01530501b034b79cf1d7@[206.106.147.12]> pjrose@servtech.com
>>>>(Phil/Judy Rose) writes:

> I know the importance of minimizing any intake manifold leakage and thus
> had  replaced the dipstick's O-ring when I noticed that dipstick removal
> had no effect on idle. Now the idle sags momentarily when the dipstick is
> pulled. But how about the filler cap? When I remove it, the engine stumbles
> seriously, but seems to quickly recover--no stalling-out. Is this the
> expected behavior if the system is otherwise tight? I suppose if I'm
> loosening the cap somewhat slowly, the ISV may be able to compensate? '89
> 100

>>You have a vacuum leak that has been compensated for (by a lazy dealer)
>>using
>>the mixture adjustment.

>>What is supposed to happen is that the breathers from the engine should be
>>clamped off while the mixture is set, then they should be re-attached and it
>>should make no difference.  If it _does_ make a difference, find the leak.
[snip]

I went searching for a leak as suggested--actually just poking around
briefly here/there with propane and turned up nothing. However--lo and
behold--when I  re-tested (remove) the filler cap, the engine this time did
indeed stop--pronto! Only difference this time is that perhaps the engine
was hotter than before. Is a well-warmed engine likely to give a more-valid
(oil-filler) test than when not-so-hot?

Then, while idling around (mow the lawn my SO says!), I pulled the ISV
connector off, and the idle speed increased by a couple of hundred rpm (to
about 1000), which I assume indicates we have a working ISP? But when I
reconnected it, there was _no_ effect (reduction) on idle speed even after
waiting 20 or 30 seconds and even pulling a bit on the throttle to help
"reset" things. I shut down and restarted, and the idle was back to its
usual 750 rpm. Is that normal idling speed behavior for this sequence of
events ('89 100)?

Phil
'89 100
'91 200q in a few days

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