You guys are great, that said (I know cyber-diagnosis is you get what you pay for) here goes and I am sorry about length, but here are the facts:

I have had my 81 vette for about a month. General around town (St. Louis) driving and a little on the highway (10-15 miles at a time). Car runs great and smooth for the most part, except for today.

Took the car down I-55 for about 35-40 miles and decided to take the long way on an old state highway through several municipalities back to St. Louis, pretty drive, wide and curvy.

I may have one or two problems that may or may not be related. It is about 94 right now and decided with tops off to turn on a little air going down the Interstate. Engine ran just a bit past 200, no problems there right...always runs a bit hotter with A/C on.

Oil Temp ran quite a bit higher than around town (with A/C on of course) Just below the 250 mark.

Anyway, when I got off of the Interstate the A/C was turned off and the oil temp dropped to the next mark below 250 (????-Don't know what that mark is supposed to be (1/2 of 250???).

Well at the first light that I had to stop at I thought the car was going to die so I put it in neutral and it brought up the idle a bit. At green shifted into drive and away we went (had my 7 1/2 year old daughter with me). This kept happening....A/C was off. It never got better and has not happened before. I suspect either timing, Idle or vaccum problems, maybe worse. When I got it into my garage still had a rough idle until I brought the RPM's up just a bit.

The RPM's at rough idle were about 5000, I think it should run about 7-9K, right. By the way it ran as smooth as a top on the highway going and coming.

Any questions, comments etc., to tell my mechanic???

Thanks, as always......

Wes From St. Louis

 

I am hoping you mean rough idle at 500 not 5000.....there could be numerous things that could be wrong. I would first check for vacuum leaks, that is the most likely. I just reciently had a similar problem with my '71, it would rough idle after I replaced the spark plugs with a step colder. I put the old plugs back , same problem. After some troubleshooting, I found out that the ignition coil was bad (Arizona heat, I suppose). I replaced that and all was fine! I wouldn't think its anything major, but it woould be good to check it over.

 

I would start looking for vacuum leaks. There a myriad of vacuum connections on vettes and any one could be causing your problem.
It sounds like that could be your problem as damaged vacuum connections are not really noticeable at higher rpms.

 

Sorry about the 500/5000....fat fingers. What are the temps supposed to run at. I thought first that vacuum was a problem. Why doesn't/didn't that happen when I drive around town for an hour or so???? Any guesses?

Thanks as always..............

 

Bill Fisher in How to hot rod small block Chevrolets advises oil temperature should not go over 270. However this is probably in racing conditions.
More research on the internet might turn up more info. As far as why didn't you have the rough idle problem before, from your post it seems that this was the first really long run on a car you have owned for a short time.
You're probably just uncovering someone else's less than adequate repair work or it was just time for that whatever to break. When I got my '80
I replaced all hoses ,belts, and whatever else I could find that looked suspicious. I even found that the vacuum advance was faulty (hole in diaphragm).