1980 911 sc

HEY GUYS I RECENTLY GOT A 911SC AND SHE HAS HARD STARTS AND WHEN IT DOES FINNALY START IT HUNTS AT IDLE AROUND 550-900 RPM BUT MY MAIN PROBLEM IS WHEN I GIVE IT GAS IT POPS THROUGH INTAKE AND LACKS POWER.. BUT SEEMS TO RUN BETTER WHEN HOT, BUT STILL IS SLUGGISH... ANY HELP WOULD BE GRATE!! I RECENTLY PUT NEW PLUGS, PLUG WIRES,COIL,CAP AND ROTOR,NEW GAS, AND AJUSTED THE TIMMING TO 10 DEG BTDC..

Brett San Diego

Welcome to the forum.

Possible vacuum leaks, fuel pressure problem, and/or poorly adjusted mixture. After you rule out vacuum leaks, I would recommend checking your fuel pressures (system pressure and cold and warm control pressures), doing a valve adjustment, and then taking it to a shop that knows CIS Porsches for a baseline CO and timing setting. If I recall correctly, 1980 was the first year for oxygen sensors. I believe frequency valve issues might also cause or contribute to your symptoms. If it sounds like I'm speaking Greek, then you've got some reading to do about Bosch K-jetronic CIS. It has all been written before. No need for me to repeat it.

Brett

1980 911 sc

OK, well i just did a vacume test with a smoke machine and found no leaks. the fuel pressure is in the range of about 45 cold and 57 psi hot and ive played with the mixture alil with the set screw on the side of the fuel dist. but nothing changes. ok ill do some research on that stuff but can you point me in the right direction about frequency valve issues? also my car was shipped from germany new, it was never in the u.s will that make anything different than u.s sold models? some things i looked at on other cars of the same year and type looked differnt.
thanks

also i keep hearing that ajusting the WUR will help? how do you do that?

1980 911 sc

thanks

Brett San Diego

My 78 SC doesn't have a frequency valve, so I haven't had to pay much attention to that part. I'm sure if you search "frequency valve" you'll find a good education. It is the part that is responsible for adjusting mixture based on O2 sensor feedback. My understanding is your kind of intake backfiring is often associated with a lean mixture.

Try searching over on the pelicanparts 911 tech forum, too, especially for warm up regulator modification stuff. I don't know if your control pressures are within spec. My CIS book is buried at home. I'm not sure I could even find it right now. I'm sure someone else can let you know shortly.

Here's some good reading about CIS injection.

http://jimsbasementworkshop.com/CIS/CIShome.html

Brett

cscrogham

Head studs. Sorry!

Houpty GT

Certainly possible but not the only problem here. You can remove your valve covers to check for broken lower studs and do a valve adjustment at the same time. If your car is popping through the intake you may likely have a blown airbox. This would cause a vacuum leak. Do you have a pop off valve? http://www.paragon-products.com/prod...110.904.wo.htm


Your surging idle indicates it is rich but this usually gets worse as the car warms up. Use you finger to see what happens if you raise the air flow plate slightly and if you lower it slightly. This will show you the effects of richening and leaning.


Sounds like your car was neglected by the previous owner and you are going to have a lot of problems to fix. A lot can go wrong with CIS before the car stops running.

I also heard that the euro cars did not have the lambda system so there will be no frequency valve. Can someone confirm this?

theiceman

i certainly wouldn't be throwing out the head studs comment just yet but granted it is worth checking and you could save yourself a whole lot of diagnosis .. I hope you didn't buy this car as " just needs a tune up" as the PO i would think knows exactly what the problem is.