My First Problem...
 

Here's the scoop...

'82 911SC...worked fine until after this weekend, now once at operating temp. the idle will surge to almost stalling to around 2k RPM, then down to almost nothing again and then it'll stall...one thing I did notice is that if I remove the oil cap it'll run...strange...the only thing I have done is I added 1-quart of oil because she was a little low after 3k miles...

:confused:


edit:

jmohn made a good point below and I was aware of this, so shoot away :)

Don't be offended, just checking, you do know you must check the oil with the dipstick (forget the gauge in the dash) when the engine is at operating temp. and running on a level surface; and that the correct reading on the dipstick is halfway between the low and full marks. Right? Lots of others have made the mistake of adding oil when they shouldn't, overfilling can cause a variety of problems the most common being oil getting into the intake and causing a lot of smoking and other possible running/idling problems.

Jerry M
'78 SC

jmohn...knew that, but thanks (I should've posted that)

there is no smoking, etc. either...

If it runs fine w/ the oil cap off, you may be running way rich when the cap is on. The SC oil tank vent is routed to the CIS boot. When the cap is off you are allowing more air into the intake that by-passes the air sensor plate. Just my guess given the information you provided. Try to lean it out a bit.. OR! your O2 sensor failed and now what was normally compensated by the Lambda circuit is now not.

If you engine start but stall at idle you should check the following

Air flow sensor plate position
Fuel Pressure
Clogged fuel injector(s) (do you use a cleaner regularly?)
AAR Faulty
Vacuum leak intake manifold spary carb cleaner and see if it affects the idle
Faulty full throttle switch or incorrectly adjusted (1980-1983)

In addition to what SOUK already told you.

Schuey, my 79 did the same. John Walker diagnosed it, just as Souk said as a rich condition. Try leaning it out a bit.
Best,
Mark

If it was running fine before this weekend leaning it out may help but the problem is still there. I would try to find out what is causing the rich condition before leaning it out.