It's that time of the year AGAIN! (CIS)
 

Get ready for the CIS start-up questions to come rolling in.

It's discussed every year in the spring and in the fall....

What happens during this time of year? Take a guess...go ahead...

I'm new here so clue me in. Are you suggesting that people begin to have problems with their CIS in the fall/winter? Is so, I'm guessing it's WUR related?

That's a part of it....why?

Cold Start Valve would be the other part. Colder temperature being the likely cause. But, I have a feeling this is a little more technical of a question?

Extended temperature changes make things expand, crack, stretch, shrink & corrode. I've observed the same phenomena during the seasonal changes as well.

Yes! The ambient conditions are changing! The CIS sub-components, such as the WUR and the AAR are being affected and they will start to work differently now that that the morning temps are so low. What was fine when the morning temperature was 70 is now not so good at 40 degrees. Some of you are lucky and your WUR or AAR are not so finicky. I have heard reports of finicky CIS engines when they were new from their original owners. It's unreasonable to expect our 20+ yr old cars to be consistent over the wide temperature range.

Think sticky AAR valves, stiffer WUR springs and system pressure spring, harden diaphragms, vacuum leaks, internal air leak, etc,..

Some of the later CIS cars (80-83) with the Lambda circuit should be able to compensate better. But even those cars have a limit to how well the frequency valve can help.

So don’t start fooling around with the CIS components, when all you need to do is richen up the idle mixture. Why richen? The cold air is more dense, so if your CIS was set up to idle well cold during summer months, with the idle mixture on the lean side…what happens now? It’ll be too lean to idle well. Crap our CIS engines love to be rich, right? Denser cold air is nothing new and shouldn’t shock anyone, but when our cars start to act up, the whole Porsche wrenching mystique gets us thinking the worst….

Colder air is usually drier too. I'm sure humidity and the state it's in (liquid or solid) have an effect as well.

Funny, I just gave my mixture screw a little tweak this morning (richer). It fired right up into a nice idle. Also eliminated the lean surge it had yesterday.

It's getting cold here in NJ, but my 3-mm allen wrench was ready for it.

Ed

Right on, Rick.

I should also say that my "leaner" example above is not to be taken for granted as the only possibility. As the spring in the WUR and the diaphragm age, the WUR can cause a rich or lean idle condition. If the AAR takes longer to close because the crud in it is making the vane sticky, but the WUR is working good...then it may lean as the engine warms...

There are several combinations of things that will cause those small hassles, but the thing to keep in mind is the ambient conditions!

Hey Souk are you a CIS expert? My recently acquired 79 SC is nearing installation of it's engine that I just did a top o'haul on. While cleaning up the CIS system I noticed that it has a newer WUR (with a rebuilt sticker on it) that does not have vacuum ports on it. After searching I have concluded that it is a newer post '79 WUR. The newer cars used an O2 sensor to enrich the mixture during acceleration. Do I run the risk of engine damage if I drive the car w/ out the proper WUR? Can I assume that the acceleration will not be as good as it should be?

I posted a thread on this a couple days ago and no one that responded seemed to know whether or not this is a big deal.

Just fishin for suggestions.

I will buy a new WUR if neccesary. But I would at least like to start this thing up this weekend.

Tim,

In a pinch I installed an 82 WUR on my 78 engine. I've got the idle mixture turned to rich, and I'm running 32 degrees total advance. With all the projects I have going on, I have not rebuilt the two 78-79 WUR that I have on the shelf. So my car has been running with the non-stock WUR for a long time. I've even driven the piss out of it at the track. The engine temperature was not unusual so I assume that my set up is fine. CHT readings would help me, but I'm not worried about it. And for just the weekend....don't worry about it.

My engine runs strong, cool and accelerates just fine.

Nope! I slept at a Holiday Inn Express last night :)

...and you probably did, too :D

Not recently Bill, but I'm to be back on the road in a couple weeks :( and not in your area :(

Re: It's that time of the year AGAIN! (CIS)
 

Souk,
I hear you can set mixture without a fancy pants gas analyzer just by bending over and sniffing the exhaust gases.

Are you going to demonstrate this before or after the cart race Sunday?

I'm in Ohio and mine starts and runs fine

n00b question,
SO where is this mixture adjustment screw exactly.? Pic please.
Tim

Suter: My nose is out of calibration :) But if you want, I can tune that beast of yours in trade for a drive :D

jlandeth: you are one of the lucky ones. I don't usually have to fiddle with mine, but I know when it changes. There are more cases of the lucky ones than there are the unlucky ones.

Tim: If you search "idle mixture screw" you will find a lot of pictures. Some of which I posted for "n00b's" such as yourself :) If you do find it, link it to this thread...or I'll do it later....later later.

Mine is running better now in this colder weather. Must have been too rich all summer long.

This is the only pic I could find. I will do a hands on and post a bigger one.



link