New (I think) CIS idle symptom
 

I've followed all the CIS and idle threads with great interest (especially the ones regarding replacing CIS with an EFI system) over the year(s), since my idle fluctuates during the winter occasionally, but today I think I noticed a totally new symptom.

The strange part is that it happens when the car is already at operating temperature, but only during the first few minutes after a warm start.

What happens is that the idle dips down below its stable 900 RPM point for about 10 seconds, and then back to normal for 10 seconds, etc. The cycles last much longer than the typical idle swings during warmup, which I plan to address tomorrow using John Walker's advice from yesterday regarding a possible rich condition.

The fact that it happens when the engine is already warm, but only during the first few minutes after a start, and the slower cycles makes me wonder what component it could be.

I know the AAR and WUR operate when the engine is below operating temperature, and the AAV operates for the first second of startup, but what component can affect idle speed in such a manner when the engine is already above operating temperature but only for a minute or two after startup?

Olivier

Anyone experience anything like this?

Oliver, I have the same problem. I am going to disconnect the O2 sensor and see if that helps. 81'SC

I've driven both with and without the O2 connector connected, and it seems to be the same. The O2 circuit is the only one I know of that has a 2-second cycle involved in it, so I think it is involved.

I checked my plugs and wires today, and also set my timing, mixture, and idle to see if that helps.

My O2 sensor is providing voltage in the spec limits, but at the high end of the range.

I think my tuneup today convinced me to get a new O2 sensor, new plugs, and wires.

I have been researching the wires this evening, and the choices are overwhelming, especially since they are all so expensive and some seem to make things worse.

I wouldn't mind building my own, but I'm not sure if the SS shielding and ground straps I have now are necessary or not, or if they can be transferred to new wires.

Olivier

I have a set of Magnecor plug wires without the shielding with no problems. If you want, you could unscrew the Beru connectors and slip off the braided shielding and add to a new set of wires. Interesting on the O2 sensor. Just had car smogged and my CO is at .6% I don't know if going a little richer will cure our warm run problem.

I'm not sure. My plugs looked like I was already rich (or my sparks are too weak)

Using the dwell meter on the O2 connector, I had to adjust the misture screw clockwise, which I think is leaner.

I do need to get an EGA and do the mixture that way, though.

Olivier

No No, turning the allen wrench clockwise richens the mixture.

OK, that helps. I will have to set it right using an EGA to be sure anyway.

Thanks.

Olivier