High Idle on Start up
 

My '91 zr-1 will idle 1500 - 2000 rpm right from start up in the mornings and stay there until the car warms up. After it reaches operating temperature, the idle will drop down to about normal. Any ideas. Doesn't happen al of the time.

I had a High Idle that turned out to be a Vaccum leak under the plenum, however my high idle never settle down to normal RPM's, it might be the ECM Chip do you have any after market chip?

did the 91's have the same high idle problem as the 90's that went away if you changed the prom?

Yes they did.

http://www.zr1netregistry.com/ZR1_issues.htm#2

Look for the part # on the mem-cal

I think this is the updated Chip # 16193416 for 91

Or you just just get an after market one from mark haibeck or someone like that