Please help! Having issues with my porshe.
 

Hey all,
New to the porshe community. I have a 79' 911 SC. Car ran fine when I bought it. Now all of a sudden the nightmare has began. When I start the car it runs great at 2000rpm and above. Below that wants to stall, runs rich, backfires, sputters, etc... Don't know if its a cold start issue. Ive checked for vacuum leaks. Ive replaced the O2 sensor. Replaced the fuel pump relay. now Im scratching my head. Also at cold start the idle goes up and down on its own. Once the motor is warm it runs rough and wants to stall. Thanks for any input. Will

'79 shouldn't have an O2 sensor. Post an engine number.

On the door jam it states 10/79. On the registration it states 1980. So did an 80' have an O2 sensor? because I changed one.

post a picture of your engine. with the info provided there is no way we can really help you

Have you change the fuel filter ?
Check your ignition wire set (in the dark ).
Check your spark-plugs.
Check the fuel pump.
Check the injectors.
Check the ignition head.

Look under the passenger seat if you see a box bolted to the floor you have an 02 sensor. Do you see an air pump on the left side of the engine? If you do you don't have an 02 sensor.

You need to get a set of gauges to look at the CSI system pressure. Could be the air valve.
Do you have a copy of Bentley for the SC?

Porsche.....not Porshe....sorry, I couldnt stand it :)

How did we miss that? O.K. no more FREE advice until the O.P. learn to spell the name correctly.

Do you call it a Por-sha or a Porch? Be careful how you answer this question, you can have the rest of the 911 owners on this forum p.o. with you.

backfire indicates a lean condition.

Welcome to the Forum!

You will find just about everything you need to know on this site by using the search feature. Any problem you have, someone else has also had it and the Pelicans on this site have been very generous with their knowledge. The solution to nearly every problem can be found here with photographs to help illustrate.

In my humble opinion, this is the best website on the Internet for a Porsche owner who wants to repair his/her own car. Also if I have to bring the car to a shop for jobs understandablely beyond my capabilities, I have some idea how to explain what I think may be the problem.

I purchase parts from Pelican to support the site. And, I bought a copy of Wayne's 101 Projects which is a fun read and a great way to get acquainted with the car.

Please take out your digital camera and show us your car! We LOVE pictures here. The engine picture that surflvr911SC was asking for will tell us which motor is in your car. A 1980 should have a 3.0 liter engine with CIS that does not use an 02 sensor, but it may have been replaced with a 3.2 (which would need an 02 sensor if it has Motronic ECU).

Don't worry... You are in the right place to find the answers you seek. Anything mechanical can be repaired. :)

Welcome willum....tough room...tough room.

Sounds to me like a mixture problem. I think you should check all your adjustments. Start with your timing, then idle speed, then fuel/air mixture.
Did you leave your car out in the rain? Sometimes mine would do it after a good rain. Now I have a garage. yeah!!

i have a 1982 it's 3.0 it has a o2 sensor!

My 1980 3.0 also has an o2 sensor.

That's because 1980 is when the O2 sensor was added, at first he said it was '79. I think that it's been clarified now that he has a MY 1980 and probably has the stock '80 3.0 w/ O2 sensor.

We just needed to know where to start.

I was looking for an engine number, not an engine picture. But yes, we do like pictures.

Kinda sounds like a vacuum leak somewhere... check the other posts for likely leak areas & hot to test. Check your hoses of course to make sure they're not disconnected or cracked.
Welcome to the forum...

regards,

jlex.

Ok everyone, cool your jets! I know its Porsche. Just a misspell. I will take pictures right now and get them posted. To answer most questions..... It does have an O2 sensor. It does have the O2 sensor box under seat. It recently had a tune up, points, cap, plugs. I checked for vacuum leaks, but I can check that again. I don't know if I have a K injection or if its a CIS injection. One other thing to add that may help, if I idle up to 2000 rpm and hold it there, sometimes the rpm will rev on its own, I take my foot off the throttle and the car runs perfectly fine after that point. Then an hour later you start it again and its back to running rough. ??? Thanks for all the input. Will

cis is k jetronic they are one in the same

Along those lines, did it backfire just before it started behaving strangely? Could be a cracked airbox. Not uncommon. Has a popoff valve been installed? It would look like a little toilet seat under the air cleaner.

Well first off, welcome! And since you bought the right kind of 911 (SC), welcome to the plot. Email me for more info on that one.;)

Now, about your problem... not to discount any other suggestions, but are your clock and dome lamp operating normally. Your problem kind of sounds like what happened to mine when the fuse blew on that circuit. It affects your CIS as well. Anyway, should be a quick check.