Couple of CIS ?'s

[pete3799]

This is a 79SC that runs great with the exception of cold idle surging. Been doing this since i got it. Idles fine when warm.
Pressures are all in spec. so i decided to see if i could adjust the mixture as the surging has gotten worse since the weather has cooled off. Only problem is i can't find the adjuster with my 3MM allen wrench. I've tried every angle i could and can't seem to find it. Is it possible that it's a different size? There is no plug in the hole just can't seem to find the head of the screw.
Also the vacum hose that goes to the dist. is coming from the left side of the WUR
is this correct?

[Dr J]

The allen wrench should go in straight and it should drop right in. If it doesn't work, I would double and triple check that the wrench is indeed 3 mm. I had the same problem and it turns out the allen wrench I used was not 3mm. With the right one, it's not too hard. Also make sure it is long enough.

The connection to the WUR is wrong. The hose in the top of the WUR goes to the throttle body on the side closest to the fan (if you are looking into the engine, it would be in front of you).

The WUR lower hose is a vacuum hose and goes to a black round thermoswitch on the drivers side, closer to the front of the vehicle.

[pete3799]

I checked the wrench with a caliper.
Hmmmm....I'll have to check my hoses. Where does the hose originate from that goes to the
vacum advance?

[tcar]

Cold idle surge is often from running too rich.

Get a flashlight and a dental mirror (at auto parts store) to find the screw.

[47silver]

easier ifyou remove the filter housing to get it the first time...

[T77911S]

the allen could have dirt in it. you are using a long allen i presume.

surging got worse when it got colder? thats strange.
one way to verify the WUR vacuum connection is to remove it with the car running. the CP should drop about 1bar.

perhaps you should post CP's.

cold with no vac
cold with vac
warm no vac
warm with vac.

[Paulporsche]

As was mentioned, the screwhead may be clogged. Try inserting the wrench into where it feels like it should go and drizzle a small amount of WD40 down the shaft. After a while remove the wrench and try reinserting it. You can repeat this if necessary. You can also try to insert a sharp piece of or any other type of thin pick down there to clean out the head.

Make sure you then plug the hole to keep out other foreign matter.

[scarceller]

You will also surge during cold if you have to much ignition advance. Be sure your distributor ignition advance is set and working correctly. If idle speed increases during cold warmup cycle then usually the mechanical ign advance will also advance timing a bit. I have done lots of experimenting with cold start on these engines while doing EFI setups and found 2 things cause surging, to rich mixture and to much ignition advance.

[tcar]

If the mixture has never been adjusted, there is a plug in the mixture screw that you must remove.

Again, do the flashlight and the 'dental' mirror thing.

You do NOT need to remove the air cleaner housing.

[calling911]

Originally Posted by pete3799

This is a 79SC that runs great with the exception of cold idle surging. Been doing this since i got it. Idles fine when warm.
Pressures are all in spec. so i decided to see if i could adjust the mixture as the surging has gotten worse since the weather has cooled off. Only problem is i can't find the adjuster with my 3MM allen wrench. I've tried every angle i could and can't seem to find it. Is it possible that it's a different size? There is no plug in the hole just can't seem to find the head of the screw.
Also the vacum hose that goes to the dist. is coming from the left side of the WUR
is this correct?

Its rich. Counter clockwise 1/8 turn until it goes by by.. make sure you blip it a few times between adjustments.

Have a nice day.

[Dr J]

The vacuum hose originates behind the throttle body if you are looking at the engine. From there it goes to the decel valve and the thermoswitch I was talking about. From the black round thermoswitch it goes to the bottom of the WUR.



I marked out the thermo-time switch and the WUR vacuum connection. Ignore the fact that I put a clamp on my thermo-time switch.

Hope this helps.

[LUFTMAN]

Check for vacum leaks at injector o-rings and injector plastic inserts in intake manifold runners also manifold base gaskets. Spray a little bit of brake clean at areas and see if car speed increases or runs rough also check intake manifold connector sleeve rubbers. Make sure air box has no cracks these models are know for these problems.

[T77911S]

DR J, that is the thermo time valve (TTV). i dont know if you know, but it looks like your vacuum assist for the brakes is not connected.


if the TTV is bad, it can cause the CP to drop. check for vac at the hose going to the WUR.

[scarceller]

There are 2 common causes for surging on cold idle, 1 already clearly stated:

- to much fuel (rich condition)
- or to much ignition advance

But these 2 are not independent of each other. Rich mixtures need less ign advance to achieve max torque. Likewise lean mixtures need more ignition advance to achieve max torque. Flame front (speed) travels more quickly with rich mixtures and less quickly with lean mixtures.

So of the 2 possible variables the one that can drift off course more easily is fuel. So I agree that most likely you are running overly rich during cold start. But just be aware that you could also have a ignition timing issue although less likely. Just to be safe double check the ignition timing is properly set.

[calling911]

Originally Posted by scarceller

There are 2 common causes for surging on cold idle, 1 already clearly stated:

- to much fuel (rich condition)
- or to much ignition advance

But these 2 are not independent of each other. Rich mixtures need less ign advance to achieve max torque. Likewise lean mixtures need more ignition advance to achieve max torque. Flame front (speed) travels more quickly with rich mixtures and less quickly with lean mixtures.

So of the 2 possible variables the one that can drift off course more easily is fuel. So I agree that most likely you are running overly rich during cold start. But just be aware that you could also have a ignition timing issue although less likely. Just to be safe double check the ignition timing is properly set.

I agree and will add that I could tell you several band-aid approaches to this problem but I wont cuz your car is rich and needs to be leaned out slightly.. I bet 1/4 turn MAX... you'll enjoy better MPG too.. just do it. BE SURE AND BLIP THE THROTTLE SEVERAL times between adjustments..

I didnt want to believe people when I was told this same thing... its sounds hard to do but its easy.. just buy the allen tool from our sponsor. Im still using my filed down wrench.. lol.. should buy one..

Also, I need to adjust mine a few times a year.. these cars are old and things change... you can spend hours and hours hunting down a MINOR vacuum leak that WILL NOT hurt anything while your throttle is being used but screws the idle.. just do it.

Also, CHECKING the ignition advance is a 10 minute job.. why not? Setting it can be a pain but if its off its gotta be done... 10 minutes to KNOW.. JUST DO IT.

Adjusting CIS mixture becomes like the ol'e matchbook set the points trick after awhile.. I just tweak mine without even checking it now. Im guessing (but dont know) even barometric pressure effects this stuff over the length of a year.