Another CIS riddle solved, over lean condition

Scott R · Scott R's Garage

For the archives and for anyone else that has this problem. After re-installing my motor, due to overwhelming oil/air leaks I had a bad drivability issue.

My 911 would start and run fine cold, and would run fine until I parked it to say go into a store. I would start it then after about 30min and it would not idle, it would just die. However it would run fine at or above 1k rpm's.

Solution, I was over lean according to my mechanics gas analyzer, I was a full percent too lean in fact. On my CIS system this equated to a quarter turn toward rich, with the O2 sensor disconnected. And then an adjustment of the idle set screw to get it where it was supposed to be.

Dave Taylor · Dave Taylor's Garage

Thanks, Scott. I'll file that away for the day my CIS pulls that on me.

Scott R · Scott R's Garage

Exact numbers were 1.6 reduced to .06 for correct operation. (I just looked at the receipt)

Paulporsche · 08-19-2005, 06:31 AM

If those are your CO numbers, then going from 1.6% to .06% is actually leaner. Are you sure it wasn't .06 raised to 1.6?

BTW are you running a cat?

Scott R · Scott R's Garage

Yes, I am running a CAT, I'll ask again today, I need to stop by there and get a part anyway. I think the receipt is backwards, since they were in kinda hurry.