OK, but did you check the Fuel Pressure Regulator vacuum hose right after you shut the car off?

If your car is still exhibiting a significant change in idle speed or quality when you remove the oil filler cap, you almost certainly have a vacuum leak. That is why I keep asking you to look at vacuum related components, and suggest the propane test for leaking gaskets.

You may have other problems, too, but you should NOT be able to change the idle quality by opening the oil filler. That is not a normal condition.

Still, there may well be something I am overlooking here. I'll see if I can find some better qualified help for you.

OK, got some help from a smarter mechanic.

Is your car losing oil between changes? Do you notice any smoke out the tailpipe? The reason for asking is that worn intake valve stem guides and seals can create a connection between the intake manifold and the crankcase that might explain or contribute to the idle problem. It could throw off the vacuum/pressure balance that the PCV valve is trying to maintain at idle.

But this kind of wear would not normally be expected at 83K miles. Did you buy this car new? Do you know the oil change history, or of any overheating incidents?

i baught the car off my grandmother the car was babied i baught the car with 56k miles tune up once a year oil chance every 3k miles no smoke out the tail pipe only when cold but thats like condensation. i checked the vaccum hoses coming from the fuel pressure regulator no fuel in them. i really have no idea and neither do any mechanics im gunna do the propane test tomarow.

Here is what better mechanics have to say about your problem:

If it turns out that you have a leaking lower intake manifold, the propane test will only reveal a breach from an intake port to the atmosphere. If the breach is between an intake port and the underside of the manifold (crankcase), the propane test will NOT reveal this. The lower intake manifold gasket commonly fails on these cars, but usually results in coolant in the cylinders and oil. If you are still running your original upper intake manifold, it is time to change it and your lower intake gaskets anyway. See this info: http://www.bonnevilleclub.com/forum/...e=article&k=38

what are lim seals lower intake manifold? the propane test showed nothing this morning then i tried it with carb cleaner and nothing.

Yes, sorry about the jargon. LIM= Lower Intake Manifold

So it would appear the gaskets are not leaking to the atmosphere. Did you go around the throttle body UIM (upper intake manifold) seal too? If you cannot detect any change all around the outsides of the intake seals, then I would do the compression tests dry and wet (wet = with several squirts of oil on top of the piston through the spark plug hole to temporarily seal the rings) like willwren suggests and see what you get.

i checked around the throttle body and around the intake manifold , and nothing. But it does sound like air is leaking neer the pcv even though its all sealed up. It might just be the belt though im not sure. i will go out in do a compression test in a few minutes and see what turns up.

You can isolate the sound you are hearing near the PCV valve by using a length of hose. One end placed to your ear and the other near the PCV or other areas until you can tell which is making the sound.