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

[pjrose@servtech.com (Phil/Judy Rose)]

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

Phil

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        Phil Rose
                        E-mail: pjrose@servtech.com
        Judy Rose
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