308gtsi went to 3000rpm after warm up

Try to block the hose beneath the expansion tank. It supplys air to the auxilary air valve.
When this valve sticks open (or is not powered) it will give a throttle effect. Just put a clamp to it and see if it has any effect on the revs.

 

The fast idle air valve is above the thermostat housing. Take the small vacuum hose coming from the vacuum switch to the valve and connect it directly to the vacuum port on the intake plenum thus bypassing the vacuum switch. This should close the valve while the engine is running. See it that helps.
AND fill out your profile please.

 

Larry you mentioned you had the car since new. If nothing was worked on recently, then I would agree with an air leak or solenoid. The fast idle air circuit mounted on the passenger side of the engine has many hoses and a few solenoids. The one valve can be closed by hand to test, the one with the vacuum line going to a solenoid. If the yellow light is out and the valve is open then one of two issues. Air vacuum or electric solenoid failure causing the valve not to close. Also check the temp switch on the water tank the one with just the wires make sure one did not get knocked off.

 

There is also a small, brass, 2-prong, on/off thermo switch screwed into the underside edge of the coolant expansion tank --- it controls the "fast idle warm up" functionality. Yours might be bad. You can test it by disconnecting the leads (to simulate the open condition), and then jumping them together (to simulate the closed condition), and seeing if that has any effect on the problem ---- if it does, the switch is bad.

 

I like this method. try it. Top be sure, this is not the "thermo-time" switch for the CSI, right?

IIRC, the 328 switch on the expansion tank controls the AAV; might be same as GTS/Bi. 328s also have an oil temp switch on the bottom front of the engine block that governs the AAV.

 

No, it is not. On the injected 308s, the thermo-time switch (for CSI) is on top of the engine block. It does several things, one of which is to control the open/close of the AAV.

The switch I refer to (in the expansion tank) does several things ---- During the "cold start / fast idle warm up" condition, it sends a signal to the DigiPlexes which advances the ignition timing, and it also operates one of the manifold vacuum supplied electrovalves which in turn control the "cold start air valve" allowing more air to bypass the throttle ---- both changes are what make the engine automatically race up to about 3K RPM for a while until warmed up.

All of this is for emissions control purposes, and only applies to the US-spec injected 308s.

The 328 (for all markets) does not have any of this particular equipment --- it has an entirely different, and more sophisticated, set up for controlling "cold start idle" emissions, and thankfully does not employ the 3K cold race up function (which is not too great for wear on a "cold" engine, IMO).

I have disconnected / removed this entire system on every 308 that I have owned.

 

Just a small clarification -- it applies to 1980 to 1983 US-spec injected 308s (which are K-Jet without Lambda); it does not apply to 1984-1985 US-spec injected 308s (which, like US-spec 328, are K-Jet with Lambda).

 

@ LARRY ---

Any luck ?