Hunting cold idle after tuneup

[Racekar]

I just did my first full tuneup of my 86 Carrera, bought the tuneup kit from our host and some magnacore wires. Other than taking way longer than I thought it should it's done. It never idled well until it warmed up, but now it has started to cycle from 600-1200 rpm when started from cold and continues this untill it warms up. I assume it has to do with the cold start function of the FI but I don't know where to start. Once warm it runs great.

[scarceller]

Originally Posted by Racekar

I just did my first full tuneup of my 86 Carrera, bought the tuneup kit from our host and some magnacore wires. Other than taking way longer than I thought it should it's done. It never idled well until it warmed up, but now it has started to cycle from 600-1200 rpm when started from cold and continues this untill it warms up. I assume it has to do with the cold start function of the FI but I don't know where to start. Once warm it runs great.

Not sure what you changed in the tuneup, please list the parts.

The 3.2L engine hunts when cold usually because it's running a tad rich. Have you checked base fuel mixture or have you touched the base mixture screw in the AFM during the tune up?

They also can hunt if the CHT sensor is out of spec.

[DRACO A5OG]

+1 as Dr Sal wrote:

but a quick check, next time you start, open the lid while on and take a screw driver and tap on teh Idle Control Valve ( ICV ), if it clears up then it needs to be serviced.

List the parts so we can see what kind of tune you actually did.

Jim

[scarceller]

Also be sure you did not disconnect the vacuum line that goes to the Fuel Pressure Regulator, be sure it has vacuum. If the FPR does not have intake vacuum at the line then you will run rich and idle will hunt on cold start.

[Porsche 2]

Had same issue. Solved by checking: 1) all vacuum hoses not leaking, 2) removed and cleaned (with carb cleaner fluid) the ICV, ensuring the valve "rattles" (moves) when I shook it, and added a little WD40, 3) turned small brass "mixture control" bolt/screw clockwise till fully shut, then turned it back out three revolutions to set a base starting point. No more cold idle hunting.