NEW CIS Problems
 

On the right side of the air box there is what looks like a hose connector with nothing on it that goes into the lower section of the air box. Should this be hooked up to something or plugged on an 81 SC? It obviously needs something becuase it is a hole going directly under the air filter. Is it this part J-219-001-30???

My second problem is the car idles fine, revs up fine, CO was set this morning at the local garage and is within specs...when I rev the engine, it falls below idle and then comes back up. When the AC is on it will stall. I can also get it to stall without the AC if I rev it over 3500. It will also stall on a hot start if I do not catch it with the gas before it falls through the idle range.

I have tried spraying carb cleaner on some of the vacuum connections. When I hit a couple of spots (the cis boot) and one of the intake runners it will spudder a little but. I would have thought that the carb cleaner would raise the idle if introduced into the system through a vacuum leak???

I am getting very frustrated and hope that someone can point me in the right direction.

Thanks,
Jay Houghton

If you can get a consistant change by hitting the same spot then you have a vacuum leak. There should be NO change in anything if there is not a leak.

usually when it falls below idle and then comes back that is a sign of a overly rich mixture

It should shudder, there's a vac leak. And on the right side of the air box, there's a nipple on my air box as well and is plugged and to my knowledge it doesn't go to anything. Hope that helps. BTW, since you adjusted within specs, when you do fix the leak, your going to go rich. GL

I spayed wd40 around all my vacuum lines to find my leak. some say a cracked airbox can be found this way, but I don't wish a cracked airbox on anyone.

I have the same nipple & took a long straightened paperclip, tried to stick it in to no avail. Mine doesn't look plugged but it is.

Jay, you mean when you rev the engine, it revs up then stalls when the engine falls back to idle? If so, it sounds like faulty deceleration valve.

Doug
75 911S

I played with the mixture and leaned it out about two clicks and everything is running strong now. No more idel issues. Is it possible that a rich condition can cause this?

Re: NEW CIS Problems
 

I think you may be looking at the "flame arrestor" port. There is supposed to be a little filter-type doo-dad inserted in that hole. No hoses connect to it.

I have the same problem with the rpm dropping to 200 and a stall when I let off the throttle.

How do I check the deceleration valve?

Frank

'77 911 S

Frank,

Is your car carbed or FI? If it has carbs there is no decel valve.

Jay

Hi Jay, a rich condition can make the car stall, so hopefully you have found your problem. You should look at whether you have vacuum leaks though.

Frank, the decel valve is to the left of the throttle body, on the left side of the engine. It looks like a bell. It's about 3" tall and has vacuum lines running to it. It is designed to open when the manifold vacuum is high (foot off the gas at high RPM, ie decelerating). It allows a small amount of air around the throttle plate (same as pressing on the gas pedal slightly) and keeps the car from stalling when the RPMs fall rapidly.

Doug
75 911S

That hose you are talking about should connect right below the oil filer cap. And as far as the o2 adjust. Remember to always lean it out first and then gradually make it more rich. This adjustment is very very slight. I found that a combo of the idle adjustment and the o2 adjustment goes hand in hand everytime. as you adjust go lean until the engine almost stalls then start to richen. You will make a slight adjustment remove your allen wrench and give it gas.... continue doing this until there is no lag. that engine should rev up immediatly and then go right back to idle.