SC idle issues

[dyount]

Bear with me oh knowledgeable Pelicanites please. I'm not much of a mechanic but still like doing what I can. Here's the symptoms.

1 Car was overfilled with oil but has been drained to appropriate level.
2 Starts very well and goes through a solid 5+ min warm up cycle
3 I've looked over for vac leaks and nothing glaringly obvious
4 No ox sensor with backdated exhaust
5 Decel valve plugged

After warm up engine hunts for idle and will not run without a bit of nursing along. If I remove the oil fill there is a change for the positive regarding idle. Idle will then not hunt and even with rev will return to a solid approx 1000 idle.
Car does seem to be running fairly rich ( from smell only no co/ox/fuel equip). However car does perform on the road quite well with no stumble etc while going through gears... just stumbles and hunts when it returns to idle.

Thanks again for your help... I'm learning but the curve is rather large

[Dave Colangelo]

Typically the idle drops a bit when you open the oil cap as you are creating a vacuum leak. This would lead me to think you have no leaks since your idle changes when you remove the cap. If you had a leak nothing would happen when you remove the cap. It sounds like you need to get a proper wideband and adjust your mixture.

Regards
Dave

Sent from my Nexus 7 using Tapatalk

[markivtruck]

what year is car? cis systems changes as years went on. 81 to 83 models has a acceleration enrichment system on those models it has a seperate control unit under pass. seat by the lamda system control unit. also power supply relay under seat.

[T77911S]

sounds like you are way too rich.

check for 12v at the warm up reg (WUR).
need to have pressures checked.

[dyount]

It's an 83 SC

As of last fall it would hunt for idle slightly between warm up and fully warm running for a few minutes. Now it warms up and hunts.

Before taking it to the shop I am looking for possible reasons why it's acting the way it is.... I'm slowly working my way into doing alot of the work on it myself although not going to start screwing around with mixtures etc without the right equipment.

[tirwin]

dyount,

Has this been an ongoing issue or a recent development? edit: I see now from your answer it has gotten worse.

It is odd that taking off the oil cap (inducing a vac leak) stabilizes the idle. And it seems that historically people disconnected the O2 sensor BECAUSE it was causing a hunting idle.

I would not fool with the mixture yet.

You need to check the fuel pressures first. How long has it been since the plugs, plug wires, rotor and cap have been replaced? Looking at the plugs might tell you something useful.

Check your duty cycle at the test port and verify your timing is set properly.

That's where I'd start.

[82 SC]

I had to turn up the idle to around 1100 to keep a good idle on my 82 SC. Seems i have similar problems. When the outside temp had gotten warmer i turned it down and it was ok for a little while then started to do idle dance. SO like spinal tap I keep mine at 11. What happens if you disconnect the WUR? Just wondering as when I was looking into it a little (not much time to really get into it) i lost the clip that really holds it on. But it seems to stay put for the most part.

[tirwin]

What happens if you disconnect the WUR?

Not sure you mean. You can't run the car without the WUR. If you just mean disconnecting the electrical connection that just means it will take a lot longer to get the warm control pressure to it's max.

[82 SC]

Yes running with WUR connector disconnected. Wonder if you can have a switch to turn on or off he WUR manually like making a manual electronic choke. Sorry if this is strange talk, I come from land of old VW buses from the 60's and I am used to feathering the throttle while warming it up if the choke does not work proper. Slowly trying to understand all the NEW to me tec. ")

[Bob Kontak]

Originally Posted by Dave Colangelo

It sounds like you need to get a proper wideband and adjust your mixture.

Without an O2 sensor, I agree. Duty cycle will be controlled by sensors and switches. There will be no input from the O2 sensor to allow tweaking with a dwell meter.

If there are no air leaks there are two main culprits for the rich running. control pressure/CO adjustment.

Your control pressure must be checked with gauges. Your CO can be tweaked manually without an analyzer but if it was set rich previously to make up for other problems that have not been repaired, you are pissing in the wind if you expect to be satisfied with the results. This means you can turn the 3mm screw and lean out the richness and the other gremlins will surface that have been drowned out by fuel.

Here is my recommendation for a task list.

1. When the engine is fairly cool and running spray carb cleaner on air connections/injector seals/intake runner gaskets and search for leaks. Listen for a change in engine RPM. Spray the airbox on the outside as well. Use the red straw with the can and there is no need to douse anything. A spritz will do. Repair air leaks.

2. Spring the buck and a quarter for CIS pressure gauges and test your control pressures. Many threads on adjusting cold control pressure and a few on tweaking warm. Get the numbers and report. I can find you the pressure graphs easily enough if you want to do this. Lots of help here regarding adjustment.

3A. Is there a test bung on your exhaust system? If so, spring for the analyzer or pay someone to set your CO. I don't know if you can just stick a sniffer in your muffler and have that be adequate.

3B. Set your CO "manually" with the help of this link. With some patience you can get it way better than it is now.

CIS Idle Speed and Mixture Setting Without an Analyzer

[dyount]

I will re-test for leaks again this evening. I found 2 injector seals leaking and replaced sleeve and all O rings.
As well, I scheduled a "look see" with a wonderful local P car guy tomorrow at lunch. It may be an issue of timing and mixtures outside of my knowledge realm for the time being.
I'll post the results if they are found tomorrow.

[82 SC]

Thanks for bringing up the CIS IDle speed setting with out Analyzer post. Almost like adjusting a carb at least that is what I picture in my head. Here is the CIS video that is also helpful.
Bosch K-Jetronic (CIS) explained - YouTube

[Bob Kontak]

Originally Posted by dyount

I will re-test for leaks again this evening. I found 2 injector seals leaking and replaced sleeve and all O rings.
As well, I scheduled a "look see" with a wonderful local P car guy tomorrow at lunch. It may be an issue of timing and mixtures outside of my knowledge realm for the time being.
I'll post the results if they are found tomorrow.

OK - Good job on the vac leaks.

Actually, once you get through this, you should not have to revisit your pressures / settings for a long time.

[tirwin]

Yes running with WUR connector disconnected. Wonder if you can have a switch to turn on or off he WUR manually like making a manual electronic choke. Sorry if this is strange talk, I come from land of old VW buses from the 60's and I am used to feathering the throttle while warming it up if the choke does not work proper. Slowly trying to understand all the NEW to me tec. ")

Ok I see where you're coming from now. The thing is that without the WUR you won't have a way to adjust the warm control pressure. The position of the pin in the WUR controls the what the warm control pressure maxes out to. So if you didn't have a WUR you would be too lean on cold starts and the warm control pressure might be too high. I suspect that the warm control pressure would functionally be equivalent to the system pressure, which would be too high for proper (normal) operation.

[Bob Kontak]

Originally Posted by tirwin

Ok I see where you're coming from now. The thing is that without the WUR you won't have a way to adjust the warm control pressure. The position of the pin in the WUR controls the what the warm control pressure maxes out to. So if you didn't have a WUR you would be too lean on cold starts and the warm control pressure might be too high. I suspect that the warm control pressure would functionally be equivalent to the system pressure, which would be too high for proper (normal) operation.

I am not certain the WUR is missing. I hope 82 SC is just talking about the electrical plug.

[82 SC]

Got it, the WUR not only adjust amount of fuel but the fuel pressure too for warm up. Thanks for the clarification. Now back to regular program and sorry for the hijacked post

[dyount]

Today's update: Got a 3mm allen long enough and tweeked down the mixture a tad.. No idle hunt. As well, did read once again the CIS post of mixture etc without an analyzer.
Local P car guy had to cancel until Monday and with me working steel erection at Hershey Stadium before next weeks Springsteen concert so I don't see much behind the wheel time over the weekend
I'll re-update after Monday when my work is checked correctly by the right guy for the job. All the pressures,timing/dwell, etc was checked about 6 months ago. I just suspect the change of ambient temps needed a little mixture tweek.

[Bob Kontak]

Originally Posted by dyount

Today's update: Got a 3mm allen long enough and tweeked down the mixture a tad.. No idle hunt.

Glad it worked better.

Just know that you don't know without the right equipment.

I gave you a band-aid.

[dyount]

Exactly Bob.... I've read enough posts to know fiddling around without the right knowledge and equipment is a very slippery slope.
I'll get something back on Monday after getting my SC in the right hands.

Thanks to the knowledgeable folks who took the time to get in on helping. Someday I may be able to do the same.

[dyount]

Prognosis after Pcar guy worked on it today.... CO needed adjusted as well as the fuel mixture that I did. Without OX sensor on the car it takes a little more tweek.
As well, enjoyed the story of my mechanic having a bad day and needing to "road test" my 911 for over an hour that he wouldn't charge me for "therapy".
I paid him $50 bucks more than he wanted anyway for the knowledge and ability of someone who forgot more about 911's than I'll ever know.