940 Non-Turbo

Posted here a week or so back about erratic idling. I've now changed all the hoses (except one that still looks good) and the intake manifold gasket and there is improvement in the idling but not yet perfect. About the intake manifold gasket, I like to know the reason or causes for the oil content around the edge on the second cylinder hole and also in the same area of the old gasket when I removed it. Is there a cylinder leak or what?

About the idling, when cold the rpm would still drop and struggle to keep itself from dying out only to bounce back and then drop and up again. I notice the engine does this at least twice in the morning before steadying out.

After that, rpm will still flicker. though better than before. The rpm needle now bounce between 800-900 instead of 700-900 previously. But the sudden (though intermittent) drop to 500 is still there though frequency has somewhat reduced. I notice this happens also whenever the air cond engages or disengages itself while at traffic stop and whenever I engages or disengages the gear. Apparently a change in engine load caused the rpm fluctuations.

Is this a Throttle switch failure symptom?

Thanks all, especially to Ringlee for suggesting the I check the vacuum. Things have improved but I would still like to get it back as before.

Laozong