'82 SC Idle adjustment

[Rodney Nelson]

I have a quick question.

I think mixture and idle adjustment are just a little off.

Basically, the car will start reving higher than normal when I come to a stop at a stop light like around 2K for like 15 seconds or so and then it will slowly drop down to 1K.

I tightened up the idle screw it actually lowered the idle when I got to a certain point (I thought it worked the other way).

Now my idle is too low and the car almost dies. I can't seem to find a happy medium.

What should I do?

Should I turn the idle screw all of the way in and then adjust the mixture to bring my idle up?

Or back the idle screw off a little and ajust the mixture?

Thanks for your help,

[Paulporsche]

There are a lot of possibilities here. When did this condition start? What was the car like before?

Turning the idle speed screw clockwise lowers the speed. It shouldn't be all the way in however. Can you back it out somewhat to achieve a happy medium?

Have you checked for air leaks? Have you checked the operation of your decel valve? Is your distributor operating freely?

Have you checked your CO%? How about your control pressures?

I would first try resetting your idle speed and seeing what happens. It's also possible your mixture is slightly lean.

Let us know what happens when you back the idle screw out a little, say in 1/4 turn increments.

[mingmong]

Had exactly the same issue with my '77 C3. Something to try is 'blipping' the throttle manually (using the little lever on the throttle body in the engine bay) Rev it up to 3000 then release. Mine settled down to about 2000 but when pushing (very gently) down on the mixture adjustment screw using the allan key tool I found it then dropped down to 1000. Conclusion..sticking air flow sensor. Gave the lever a good clean with isopropanol and now works a treat. Hope this helps...
Mark

[Paulporsche]

Could even be your throttle linkage hanging up somewhere.

[Gunter]

Like Paul said.
There is a basic setting of the air flow sensor plate in the throttle body.
Assuming that all other factors are good, i.e. Components work, Ignition is good, the setting of the mixture is between the idle speed adjustment screw and the mixture adjustment screw (3mm Allen)
Rodney: If you don't have it yet, get the Bentley SC Repair Manual.
It explains the workings of the CIS, and other stuff, very nicely.
Is your '82 stock? No changes to the set-up? Stock '82's have a lot of vacuum lines from WUR to TB, Deceleration Valve, AAV, AAR, Distributor advance/retard, cruise control, etc.
I have a complete CIS from a '82 sitting here and here are the stock OEM connections:

FRONT of Throttle Body: 2 lines
One line to top of WUR,
2nd line to Distributor Retard.

REAR of Throttle Body: 2 lines
One line coming out with a T branching to bottom of WUR and, the other branch going to the Decelleration Valve,
2nd line going to Distributor Advance.

Is your timing 5deg BTDC?

[Rodney Nelson]

Hey guys,

Thank you for the replys,

I tried with no luck yesterday to get a happy medium between the both. I was going back in forth between what I assume is to lean and too rich. I could only get it to just barely idle at 650. No higher.

So, cleaning out the sensor with isopropanol. I don't have any of that. can I buy it at the parts store? Also, I assume I just remove the intake cover and clean that way?

Gunter,

Thank you for the outline of the vac lines. If I had to guess something was going wrong I would say it is definately the sensor or the vac lines. What is the best way to deal with the vac lines, are all the connections easy enough to access, should I just start replacing them?

I do have the O2 sensor disconnected and I'm not really sure where my Timing is at the moment becasue I had my wrench give it a full tuneup about 3 months ago, back then he was having a little trouble adjusting the idle down, now I cant get the idle to go back up when it seems the mixture is on the money.

I am taking it to my wrench monday morning to adjust my clutch, I just had him replace it a week ago. I didn't feel like attempting the 20 hours worth of work for that job.

Anyway so I might just have him look into it but I wouldn't mind checking out the vac lines and cleaning the sensor before I bring it to him.

Thanks for all of your help,

[Gunter]

Isopropanol is Rubbing Alcohol, available in any grocery store/pharmacy.
Mark: What exactly do you mean by: Sensor?
I don't see how cleaning the airflow plate with rubbing alcohol would make any difference. When this plate sticks, it means that it misadjusted and rubs against the throttle body.
Rodney: Before you replace any hoses, ask your mechanic if he thinks a quick check for a vacuum leak might help. However, a vacuum leak shows up as rough idle. If you don't have that, it sounds to me a matter of timing, idle speed, and mixture.
Is the retard on the distributor connected and working?
Can you let the mechanic confirm that the set-up (Vacuum lines) is unmolested and strictly stock?
On these engines, there are so many vacuum lines; add to the above the brake booster (Servo) line coming from the TB and going to the front.

[Rodney Nelson]

Yeah,

Man I guess I just have to re-research this stuff. The retard is hooked up. So I need to see where this things timing is. It is not really idling rough, well a little but that is because it is only at 600 rpm. I feel as if I have no idea where the mixture is........

How is everything supose to be set again? O2 sensor disconnected and timing at 35 degree with retard disconected?

Definately a good idea to have him see if there is a leak while he has the car and to check the lines. It does seem to have the original blue and orange vac lines.

[Gunter]

My Ox sensor is permanently disconnected.
Some people set the timing at the extreme advance-range, I don't.
I stick with the basic 5-7deg BTDC at ~900 RPM and play with the idle speed and mixture screw.
Strictly by ear: cw on the 3mm screw is richer, ccw is leaner.
I turn small ammounts cw until it coughs, then I go ccw until it coughs again. The right setting for me is inbetween. It only takes about a half-turn between richer and leaner.
Do not leave the Allen wrench in the hole when revving.
A richer setting is preferred; JW recommends 3.5% if a gas tester is used.
If you can run down to 600 RPM without too much fuss, you don't have a vacuum leak.

[Rodney Nelson]

Gunter,

Thanks, so it looks like from here I should bust out the timing gun. Do you have the advance/retard line hooked up?

So this is what I am going to do.........

1) set timing between 5-7 ( do I do that with the advance hooked up?)
2) set idle screw to get me around the 900 mark
3) then adjust the mixture screw in the middle

Does this sound right?

I think the only thing that I have in question now is the advance/retard lines. Do you have them hooked during setting the timing and do you have it hooked up when you are all done?

Hooked up during timing test?
Hooked up

[Gunter]

Set the idle to ~900 first, and see where your timing is now.
I found no difference when leaving the advance/retard lines connected as long as you don't rev more than ~900. Try it yourself by pulling the advance off when running.
If you disconnect any one line, you'll need to plug them because now you have a leak.
I use a timing light (Stroboscope) to set at 5-7 at ~900, all lines connected, adjusting several times the idle speed and mix.
Re-check the timing after you are happy with RPM and mix..
I run 91-92 octane.
Keep your distributor happy by removing the cap and rotor, remove the small felt-plug and put a few drops of oil in there, replace the plug. Feel the play on the shaft, there should be none or very little.
I also put a little oil on the plate to ensure that it moves freely.

[Paulporsche]

Is this happening while the engine is fully warmed up?

Were you finally able to get the idle speed up to 900 or so? Sometimes a too low idle speed simply results from a too rich mixture, and a too high one from a lean condition.

Did you say when this condition started?

[diabolos88]

Originally posted by Gunter
Isopropanol is Rubbing Alcohol, available in any grocery store/pharmacy.
Mark: What exactly do you mean by: Sensor?
I don't see how cleaning the airflow plate with rubbing alcohol would make any difference. When this plate sticks, it means that it misadjusted and rubs against the throttle body.
Rodney: Before you replace any hoses, ask your mechanic if he thinks a quick check for a vacuum leak might help. However, a vacuum leak shows up as rough idle. If you don't have that, it sounds to me a matter of timing, idle speed, and mixture.
Is the retard on the distributor connected and working?
Can you let the mechanic confirm that the set-up (Vacuum lines) is unmolested and strictly stock?
On these engines, there are so many vacuum lines; add to the above the brake booster (Servo) line coming from the TB and going to the front.

Gunter,

I have a '88 930, stock CIS system, although my idle is hit or miss, sometimes its smooth as a babys bottom, other times it is rough as helterskelter and starts to hunt for a couple seconds. I know that means Im running rich, but I need to keep it rich otherwise if I try leaning my CO out, the car runs really rough. Could this mean I have a vac leak somewhere? Also you stated that the Brake booster(servo) line comes from the TB andgoes out to the front, well my brake pedal feel too soft and now pushes all but just 2" from the floor!
This all happened when I came down to AZ from Chicago just yesterday for my job.
any ideas?
Eddie

[djdsc]

I am sure this is covered in many other posts but this one is current. I am very curious here because I have been working with the timing and idle on my ’82 also. The factory manual clearly stated to disconnect the vacuum lines, when setting the timing, it doesn’t mention plugging them. My SC has both the advance and the retard on the distributor. When disconnecting the retard the idle increases, isn’t that what the retard is suppose to do?

So then when timed, plugging in the retard line drops the idle, as it should I think, and then resetting the idle. In order to get the idle up to the 900+/- I have to back the set screw all the way out to the stops. This doesn’t seem to be right.

So first off, vacuum disconnected, yes or no, when setting the timing at both idle and at high RPM? Plugging the lines when disconnected doesn’t seem to make a difference at idle, I haven’t tried at high RPM’s.

[DJC911]

Boy, if you guys figure this out, let me know. My mechanics had my 81 SC for a month off an on and still didn't work out the problem. Mine idles around 2.0-2.2k most of the time, except when the ambient temp is above 75F (and even then usually only at night), when it will idle around 900-1k.

The mechanics played with it, replaced the WUR (as I recall), and got it to stay down closer to 1k, but then half the time the car wouldn't idle at all. They ended up pretty much setting it back to where it was when I got the car about a year ago.

Also, I note that the engine oil temp guage seldom gets more than a hair or two past the white box at the bottom. Haven't had the guage tested, but assuming it is working properly, might there be a relationship between these two problems (i.e., does the oil temp sensor communicate to the WUR or other part of the CIS system to adjust the idle speed during the warmup cycle)?

[Rodney Nelson]

Man, I just got done out there messing with everything. I have the standard exhaust smell emitting though my pores.

Basically, I set it at 5 degrees BTDC as in Wayne's book, then I adjusted the screw out and messed with the mixture screw, it took me a while but I finally got it to idle right aroung 950, perfect!

I took it out for a drive and the RPMs did not go up like they were and everything seemed great. So, I stepped on it..............well in pinged like there was no tomorrow as soon as I hit the 5000 mark.

I give up!!!!!!!!!!

It is going to the mechanics tomorrow morning, as I said earlier for the clutch adjustment so I'll see what he can do.

Thanks for everyone's help.

[diabolos88]

Rodney and DJC911,

Ive got a 930 that I just drove down from Chicago.

Since getting here 2 days ago, I too have been experiencing your same symptoms. My idea is the atmosphere in Phoenix causes our CIS cars to run erratic. My question to you both is how long have you had this problem? Also have you ever had this problem before and if so what did you do to fix it before?

[Gunter]

Rodney:
Pinging can be from a lean mixture, or advance timing, or both.
I would have the distributor checked/recurved?
The internal springs together with the vacuum give you the right timing at various RPM's.
DJC911: With high idle when warm I would concentrate on the Auxillary Air Regulator (AAR) and AAV. Sounds like the "halve-moon" opening in the AAR is not closing. Before changing the WUR, system pressure, and control pressure should have been checked. WUR's are expensive and sometimes can be fixed; ask for the old WUR back, especially since you still have problems. Avoid places that don't do system-checks to determine the problem; anybody can change parts until the problem disappears.
diabolo88: It's my understanding that turbos need to be set rich to avoid detonation. Soft brake pedal usually means that the brakes need to be checked. Bleeding for sure and, when were the calipers rebuild? Master cylinder? How are the rotors, and pads? To check if your Servo works, with engine off, press on the brake pedal, start engine, your foot should feel the pedal going down.
djdsc: Depending on the year, timing adjustments vary.
'78-'79 has 5deg @ 950 RPM, vac. connected (26deg @ 6000 RPM).
'80-'83 also has 5deg @ 950 RPM vac. disconnected (21deg @ 6000 RPM) (The don't differentiate Adv./Retard and don't say to plug the lines)
Obviously, when you pull the retard line off the distributor, you'll have a small vacuum leak.
In my earlier reply, I described the way that I set my timing; It works for me. If anyone wants to do it differently, go for it. As long as it works.
I can only repeat: Get a Bentley Repair Manual to learn more about your 911 and experiment.