Can you replace a CIS adjustment screw?

[Blackdimonds]

After finding and correcting a vacumm leak, my 81 911sc is now running like crap at start up. The car has always started ok, but now it really struggles until it is fully warmed up. I took the car to the local shop and they adjusted the idle and air/fuel mixture for me. The mechanic said that the adjustment screw was stripped out, and it was very hard to get any kind of a bite on it (this explains why I had no luck adjusting it myself). The car ran fine after the adjustment, but as I was afraid of, the car started up like crap again tonight. My question is, can I take the air boot and feul control unit off and get in there and replace the adjustment screw? Or is it too difficult to get to? If I do get it replaced, can you tell me the best way to start over again on my mixture and idle settings?

Thanks in advance,

Paul
81 911SC/RS

[wckrause]

After your car warms up, does it idle OK? If so, then your mixture setting is fine, and you need to troubleshoot the components of the CIS system that are involved in the cold start process.

------------------
Bill Krause
'79 911SC Euro
MY PELICAN GALLERY

[This message has been edited by wckrause (edited 09-01-2001).]

[Superman]

I'm sure you can change the adjusting screw, if you can find an identical replacement. I'm pretty sure you'd have to remove the fuel distributor along with its rectancular plastic mounting plate. At any rate, you probably can see the screw if you just take off the air cleaner.

I believe that when reinstalling, you hook up the gas supply to the fuel distributor but leave the six injector lines off. Then run the fuel pump and turn the adjusting screw until gasoline just starts to flow out the injector ports on the FD, like little volcanoes. then back the adjusting screw off a little, hook up the injector lines, bleed them into a jar or jars to expel air. Start the car and finish the adjustment. Preferably wiht a gas analyzer.

------------------
'83 SC

[john walker's workshop]

the screw has real fine threads. it's not sold seperately. you would have to rob one out of a junk sensor plate at the boneyard. the whole housing needs to be removed and disassembled to get at it. the allen wrench hole in the screw fills with dirt and doesn't allow the allen wrench to go all the way in. pick out the hole with a pointed wire and blow out with air if you have it. that often fixes the problem. sounds like your warmup regulator is the cold running problem. you can richen it up by tapping the recessed plug down a few thousanth of a inch. we're talking just a hair. if you go too far,and the engine surges thru warmup, you need to pull it back up by drilling a hole dead center, 1/4" deep, thread it, install a short stud in the threads, slip on a washer that's bigger than the plug, run a nut down on the washer and tighten the nut to pull the plug up.

[lagoon]

I agree with John Walker. I had the same cold start/run problem as you and it turned out to be the warm up regulator was set too rich. After knocking the plug back out to spec, car runs like a charm. 81'SC

[Blackdimonds]

Thanks guys, I was able to get the 3mm allen to grab when i turned the car off (I think it was somewhat dirty inside the head). I was able to adjust it a tad richer, and it runs 100% better now. My home co tester tells me I am at about 1.1% now (it was at .15% before, way to lean) I have let the car cool again and will try the cold start tonight and double check if it is running ok at start up. If it is still giving me problems, I will take your advice on the warmup regulator.

Thanks again,

Paul
81 911SC/RS

[john walker's workshop]

set it to 3.5% hot and leave the oxy sensor unplugged. you'll like it better.