[VaSteve]

Hey all.
I need some help. Last weekend drove the SC to Baltimore. Ran great. Stopped to check the oil. Just a little above the lower dots. The car started running a little rough.

Today, drove about 2 miles and added a quart of oil. Drove for about a half hour and notice that the idle is rough again. I will come to a stop, it idles ~ 750 for about 20 seconds, pressure is about 1.25 on the scale and the oil gauge is now at the 3 o'clock position. Then, I can feel the idle drop to around 400-500, the pressure jumps around between 1-2 and the oil gauge climbs a little. I checked the stick and it's about dead center between the dots. Temperature appears "normal" around the 8:00 position.

I don't think the two are related, but I'm a little concerned. I read on Pelican or Wayne's book about adding too much oil and it really messing up the engine.

Anyone have any ideas? I really wanted to drive out to SP next weekend in the Porsche. If you have an idea, any time this week and a garage, please let me know. If you have an idea, please let me know that too.

Thanks, guys!
Steve

[Vicegrip]

First make sure that the oil level is right by using the method recommended in the owners manual.

You can also check your oil cap. Some (later years I think) 911s will idle rough if the oil cap is loose, the O ring is absent or bad and not making a pressure tight seal.

[Jim Richards]

Check for vacuum leaks?

[VaSteve]

Originally Posted by Jim Richards

Check for vacuum leaks?

I did a little reading. You're just looking for an excuse to do another drop.

I will check on both, hopefully tommorow. Re: checking for vacuum leaks....I'm a little leery of the part that said "have a fire extinguisher handy."


Ummm. One other thing.... Could putting in cheap gas cause this problem?

[type954]

... as long as it's premium cheap gas ....

[VaSteve]

Originally Posted by type954

... as long as it's premium cheap gas ....

No it was not. I think I'm going to start there. Though I did put in the minimum the manual said....

[GB83SC]

Make sure that you put the oil cap back on correctly and that it is all the way tight, if not you can get a vacuum leak at the oil cap.
Also make sure that the hoses that are attached to the oil filler neck are also tight.

[William Miller]

Cap is the first thing to check.

Always check oil when hot.
My oil gauge actually seems to work. Every car is different, but I can watch the level on the gauge increase once the car is warmed up. If I was to fill it cold it will be near the top of the gauge when it's warmed up.

I don't know if this is because of expansion, or it has to do something with the oil circulation pattern as the engine T-stat opens to the engine oil cooler and then the aux stat opens to the front oil cooler.

AS GB83 stated the mixture is effected (leaned) when you open the cap. It allows unmetered air into the system. The engine slows a little when it is lean. On some occasions (models) it will tend to stall. All of this is dependant on the condition of the engine and how the maitanance has been. And O' yea tempature and humidity. All have an effect.

The 83 SC's (USA 930/16 engine) have a computer to monitor and adjust the mixtures for these variations (Closed Loop)
79 and earlier US as well as ROW up to 83 have the K-basic CIS which use more crude means to adjust mixture to compensate for tempature only and enrich the ratio under load.

Mine is an 83SC ROW. I installed air/fuel meter and can watch as ambient conditions effect the A/F ratio. I can also see how the mechanical parts compensate for tempature. When I first start my car I can see it running rich and lean out as designed. I can also see that it runs lean for a while as it goes from warm (say 60 C , the top of the white box) to operating temp 85 C when the thermostats start to open.) My system leans out a little too soon.

If yours is a K-lambda (80-83 US SC) I would think the computer would compensate (Richen the mixture) for small vacuum leaks as well as when you remove the cap.

If that's the case then I would suspect the Oxigen Sensor.
There are a few tests that will pinpoint it. Can anyone with a computer confirm this? I'd like to learn more, but I don't have a K-lambda car to play with. Maybe unplug it and see if anything changes?

[VaSteve]

Well so far here's the diagnosis. When I checked the oil yesterday (according to the manual - when warm on level ground) I was 1 block from home (sloped driveway have I). Today I took the car out for a run to the dentist. Not a really long drive, but into normalish opertaing temperature range. I didn't seem to have the problem (it would dip a little in RPMs but nothing like yesterday). I think maybe when I put the oil cap back on, I must have put it back on tighter.

I will monitor the situation...I'm sure in case of a grand catastrophe, you guys won't leave me stranded on the way to SP, right, right??

For good measure, I filled up 1/2 tank of 93 octane with Techron. Too early to see the results of that.

[William Miller]

Glad to hear it's back to normal!