Question on a 1985 Pontiac Parisienne wagon

I recently inherited an '85 Pontiac Parisienne wagon (V8) with only about 100,000 miles on it. It was always garaged and generally only used for such things as road trips on summer vacations, so it appeared
to be in amazingly good shape.
Only thing is, it's turned into a maintenance nightmare, over things I *thought* would be no big deal - and now I have some questions.
Here's the story:
When I first got it, I was told that "last time it was due for plate renewal, it didn't pass the emissions test - and ended up getting a waiver, so that may need to be looked at". My first guess was that it probably just needed a good tune-up (new spark plugs, etc.), so I took it to a local Firestone dealer and had that done. When they gave it back to me, it was dying at every stop sign or light I came to, once it warmed up (but ran great when still cold). Took it back, and they finally came to the conclusion that while the tech. was cleaning some carbon deposits out of the intake manifold, a chunk of carbon must have fallen down in there and was causing the problem.
Ever since then, it no longer dies at lights, but it seems to be idling too low. My oil light flickers unless I very slightly press on the gas pedal to bump up the RPMs just a little bit, while I'm sitting at a stop sign or light. If I turn on my A/C, it makes a rather nasty grinding/rumbling sound at idle too (which again goes away as soon as I slightly depress the gas pedal).
I took it back again and complained, but they insisted there was nothing else they could do for me, and they "saw the oil light flickering too, but thought it was nothing to worry about".
I didn't have time to mess around with them any more at this point, so I let it go for a while. But then the plates were up for renewal, and sure enough, it failed emissions again! I went to a local mechanic right by my house and told him my story. He promised he'd figure it out. Well, after 4 or 5 trips to the emissions testing place and trying all sorts of things, he finally got it to pass by replacing the catelytic convertor. (He also pulled out the new plugs Firestone had just put in, claiming they used platinum plugs which were inappropriate for this type of vehicle, and swapped them with some regular plugs, and replaced the cap, rotor and wires.)
After all *this*, I *still* have my flickering oil light that nobody seems willing to address, and my rumbling A/C at idle once the engine is warm. And I'm practically convinced it's as easy to fix as making some kind of idle adjustment. Can someone advise me if this is something I can just turn a screw and do myself, or is this going to involve carburetor work or what? It's just not worth dumping more $'s in this thing!
Thanks! (Please reply on this newsgroup as my email listed is a fake.)
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First if you are going to drive a 30 year old car and have to rely on service shops to work on it you are going to spend lots of money and have lots of frustration. You need to find an old time mechanic who understands how these engines work. The oil flickering could be as simple as too light oil in the engine or a worn out engine. You need someone to do a complete check out of the engine for bearing wear, ring wear etc. You need to determine what the rpm at idle is before you can determine to increase it. If you plan on keeping the car get some books and start learning or a second job to pay for the repairs. Age has as much to do with problems as mileage and depending on environment maybe more.....

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Stupid Q., but have you changed the oil with a 10W30? I've had that exact same problem with a chev 305 and a ford 231, and exactly the same problem went away.
Vuarra
Quid quid latine dictum sit altum videtur. (That which is said in Latin sounds profound.)
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"Woody" wrote:

You mean 20 years old and that car has a chevy 305 or 350 engine which is a proven engine and very reliable. If your mech does not understand a small block chevy of that year he is not worthy of being a mech.
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If this engine is still carbureted I would think a carb kit is in order. It sounds like a needle-and-seat/float issue to make it run that dirty and idle that low (which would give you a flickering oil light).
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James, Thanks for the reply. You may be exactly right. I'll make sure they put 10W30 oil in at the next oil change, just to make sure Vuarra's suggestion isn't the answer - but I think it's more serious than that. (I know the last time it was in the shop, the mechanic mentioned that he "changed the oil a second time" in an attempt to get the oil light to stop flickering, and it didn't do any good. Maybe he just put 5W30 in both times - but you'd think, given the circumstances, he wouldn't have done so?)
It is a carbureted engine, and my folks told me a rebuilt carb. was put in the vehicle about a year before they gave it to me - and it's possible it was never really adjusted properly.
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