CIS strange idle issue

Scott R · Scott R's Garage

On my 80SC I had a funny idle issue start happening the other day, the car starts and runs fine cold control pressure is exact to spec, warm control pressure is great as well. After starting the idle sits around 950 and then after driving a bit it's up to 1900 or so. If I shut the car off for about 60 seconds and then restart it stays at 950 for the rest of the time. Any thoughts?

Idle mixture is .6% +/- .2%

Paulporsche · 05-25-2006, 01:37 PM

I would look into vacuum leaks, especially @ the decel valve. Your AAR may also be faulty. It's also possible your distributor isn't advancing correctly, or your throttle linkage is hanging up on something. If you search you will find out how to test for leaks, plug the decel, test the AAR etc.

BTW are you reqd by CO to run that lean?

Scott R · Scott R's Garage

Quote:

Originally posted by Paulporsche
I would look into vacuum leaks, especially @ the decel valve. Your AAR may also be faulty. It's also possible your distributor isn't advancing correctly, or your throttle linkage is hanging up on something. If you search you will find out how to test for leaks, plug the decel, test the AAR etc.

BTW are you reqd by CO to run that lean?

Yes, and well.. on the 80 or at least on my emissions sticker that's where it's supposed to be. I don't have any leaks that I know of I just did a complete reseal of the system a month back including a new airbox. I have a couple extra AAR's whic h is where I am leaning since it appears the my warmp cycle has changed recently. I was getting a good high startup idle then a drop off as the AAR closed, this has stopped however I figured since it was soo hot here that it was just not ever opening.

JP911 · JP911's Garage

Try pulling the vac line off of the decel valve.

Scott R · Scott R's Garage

Quote:

Originally posted by JP911
Try pulling the vac line off of the decel valve.

Good point, I suppose that could be hanging up as well. If that's the case I will have a serious debate, to either try and replace it in-car, or to just leave it disabled. I do hate having disabled items, I still run an O2 sensor after all.

JP911 · JP911's Garage

Our host sells new decel valves if that turns out to be the problem. Apparently there is also a way to "fix" the later SC decel valves by crushing them slightly. Do a search on the forum to find more details on that process. Good luck!

oneblueyedog · oneblueyedog's Garage

Check the floor mat so that it's not nudging the gas pedal. Hey, it worked for me at one point.

Scott R · Scott R's Garage

Quote:

Originally posted by oneblueyedog
Check the floor mat so that it's not nudging the gas pedal. Hey, it worked for me at one point.

Well I went outside this evening and pulled the distributor, the weights were sticking again since last summer. I cleaned them up and re-installed my acceleration sure is better now. And I am running and starting fine at .06 with the 02 sensor plugged in. I still suspect a vacuum leak however, I sprayed some ether around the drivers’ side runners and I got a jump in RPM's, it may be that ether was getting sucked into the intake however.

It's been 200 miles since I re-installed the motor and rebuilt the CIS, so I should probably go back and tighten all of the clamps again.

I also base lined and set the AAR tonight, I froze it and then knocked the pin in a bit to get the gate closed, and so that's working better as well. Maybe I am being too picky here, someday I hope to drive or ride in another SC just to see how it's supposed to actually run.