I have a code E85 and when I clear it it comes back in just a few seconds.It has a rough idle to.Here is what I have done.Pulled heads and replaced both heads gaskets and had heads checked for cracks and they resurfaced both of them.New spark plugs.New thermostat.New water pump.Drove it about 300 miles and started getting this code 85.I cleaned the TB today and I am still getting bad idle and code E85.Could it be the egr valve.Runs great off idle.
Help!

check this out:
http://www.cadillacforums.com/forums/showthread.php?t=21558

you probably have a bad ISC motor.. when i got a code E085, it was a bad isc motor causing it..I replaced th emotor, recalibrated the motor and the TPS, and the problem went away..

I would first check out the TPS.