ANOTHER CIS adjustment question- Very High idle!
 

Hi guys

Its been a long time since I posted as my car has been off the road for a few years :(

Anyways I ran it last year a few times and it ran poor. I am trying to get it back on the road. Last fall I bought an Innovate LM1 ;)

Started the car this morning. Idle was high (2500) and air / fuel ratio was 10.0, should be 14.7. So running real rich. I adjusted the small 3mm hex bolt on top 1 full turn clockwise (I did it in 1/4 turn increments) This brought the air fuel to 12.4 but brought the rpms up to 4000 :eek: at idle

I tried turning the large idle speed screw but it is all the way in so can not go further clockwise.

I did not check timing as I can't get it to idle low enough. Should I set timing at full advance???

How else can I bring the idle down? I checked for vacuum leaks and did not find any, but I know how well they can hide.

Please let me know if there are any ideas

Air must get in from somewhere in order to make idle that high. So it's either a leak or throttle which doesn't close fully. Check that throttle closes. If it does, look for leaks. Pinch or remove all possible bypass hoses which can bypass air around the throttle. If idle doesn't go down, you have big leak south of throttle.

(But leaks south of throttle usually lean out the AFR's. As you have rich condition I believe you either have sticky throttle or your bypass-valve is open)

My cis did the same thing, it had a cracked airbox, so it was a huge vaccume leak. Check the tubes behind the fuel injection. Stell tubes, for some reason the get holes worn in them. Bad holes. It something to do with the engine moving in the engine compartment that wears the holes I think.

Follow this link, and scroll to post #133
http://forums.pelicanparts.com/porsche-911-technical-forum/465760-need-more-cis-help-please-7.html

Paul had a littany of problems, including one like yours. The leak you apparently have may not be in the hard-to-see steel tubes, but here's what to look for.

You should probably just buy my complete system and plunk it on.

My car ran very well.

I have mentioned that EXACT thing to my wife a couple of times today ;) I agree 100%

Often a high idle is the result of a faulty decel valve. Remove the vac line from the top and plug it. Then see what idle you get.

Maybe a stupid question, but did you let the car warm up long enough before adjusting the mixture? Because when cold it will run rich with a high idle.

Good point, Aurel. The function of the AAR is to keep the revs high during warmup. Even so, it should only be about 2000 rpm for about 5 minutes or so from cold.

with a mixture of 10. that is very rich, if warm. it should be rich when cold.
air leaks make it go lean, unless some one has tried compensating for a big air leak already by making it run rich.
it could be a combination of things. make sure you have 12v to the WUR and the AAR. absence of 12v will keep the mixture rich and the idle hi, although still a bit hi for what an AAR can do. perhaps a decel valve problem too. do what paul said about plugging it.
you also should have the TTS (thermo time switch), if it goes bad or does not have 12v on it, it will make it run rich.
the vacuum line to the WUR, or lack of, will make it run rich, its part of the TTV circuit
check the metal pipes in the rear by the cover to the oil cooler. as paul knows, as well as mine too, they rub there and can cause a leak. it is very hard to get to so check as a last resort.

check the CSV, if it is getting power all the time, it will make it run rich.

check timing, could be advanced. if the vacuum line came off or it is connected to the wrong place, this will give you about 15 deg advance, keeping the idle hi.

this should keep you busy for a while

oh, and dont forget the every popular control pressures, which are alxo controlled by the vacuum/TTV cricuit

The AAR can stick open or not fully close and keep the rev's pretty high. The device is electro-mechanical so lack of voltage or a burned heating element will prevent it from closing just as easily as a gummed up disc [which is actually the door that needs to close] They are pretty easy to remove and test. If you look into the opening it should be partially closed. Toss it in the freezer for a couple of hours and it should be open more. Apply 12 volts to the terminals and it should slowly close completedly.
Also, once the engine has warmed up and the WUR has leaned things out it doesn't take much of an air leak to keep the revs at 2.5K. If you played with the mixture while the engine was cold I would let it get good and hot and then re-adjust. My money is on the AAR.

If the car has been sitting, the advance mechanism of the distributor might also be hanging up.

Update

I checked my AAR- did the freezer test and it was good.
I did test with CIS gauges and WUR is within spec
Timing is checked and set at 35 full advance, vacuum is plugged.

Using my LM1 I got the mixture to between 14.5 and 14.7
Replaced the decel valve with one that was taken off a good working car.

My problem is the car is idling at around 3000 RPMS Very high!! If I try to turn the idle screw in the engine will start oscillating really bad, from 3000- almost stalling about every second. And this is with just a touch of the screw.

While it is oscillating the fuel pressure also jumps around, from 2 bar to 4 bar. I don't know if this is jumping because of the idle or the idle is jumping because of the pressure.

I figure it MUST be a really big air leak somewhere, I can't think of any other parts to check, I don't know how to check for air leaks because it is idling so high already.

I am lucky and have a complete spare CIS set -up that was taken of a well running car 6 weeks ago (Thanks Unclebilly)

PLEASE HELP

Thanks

Shawn

is the oil cap on/good

Oil cap on tight

New problem, see this thread

http://forums.pelicanparts.com/porsche-911-technical-forum/481125-cis-pressure-problem.html

I had what I thought were two seperate problems, that turned into one big issue. I would rather keep it together on one thread..sorry

Shawn