Thermo time switch troubleshooting?

I wouldn't be suspecting the thermo-time switch for a low cold RPM -- it's only function is to fire the cold start injector for a second or two during starter motor cranking at initial cold start-up to give a lot of initial enrichment for cold light off (i.e., it has nothing to do with how much air, or fuel, is entering the engine during the rest of cold running).

What is the year/model/version?

 

First, please go to this page:

http://www.eurospares.co.uk/partTable.asp?M=1&Mo=662&A=1&B=38782&S=

and confirm that your euro 308QV (SN 44297 LHD?) is the later design with the AAV mounted under the coolant tank.

If so, you might try a couple of things. With tube 72 removed from fitting 13 and with the engine dead cold (like after sitting overnight so the AAV is open -- which I assume that you've already confirmed is actually partially open at room temperature):

1. try blowing into the free end of tube 72 to make sure there isn't some blockage somewhere else (e.g., tube 69 looks like it must be a fairly long hose and make many bends to get back to fitting 73), and

2. it wouldn't hurt to poke a long metal rod (like the long end of a small allen wrench) up fitting 13 just to make sure it's not blocked either.

The other possibility is that the AAV is open, and trying to let extra air in, but the cold A/F ratio is too wacky and you are not actually running on all cylinders until the RPM drops. Didn't you have a cold stalling problem after initial light-off and a 2000 RPM warm idle? Did you tweak things to improve warm idle and/or confirm that the WUR was doing what it was supposed to do when cold?

 

I'm with Steve so far. If it throttle responds but does not idle it could be the AAV. If it doesn't throttle respond well you can check control pressure cold and as it warms up. The control pressure restricts movement of the air flow plate. Higher control pressure makes a leaner mixture. You can look at the aux. air valve opening from cold and see if the restriction changes as it warms up. The control pressure regulators are very sensitive to trash in the fuel and are a common area for problems.
They can usually be cleaned and adjusted.
Cheers,
Tom B.

 

Plug the AAV hose to the manifold when warmed up and see what the idle is. The valve should close when the elec. element heats up - minute or two. it also gets warmed by engine heat. Get the idle figured out without the AAV. Maybe a warped throttle plate, poorly adjusted throttle stop, air leak, or as you said throttle spring trouble.Try disconnecting the throttle cable. If you can get warm idle straight, then put the aav back on line and see if it raises cold idle. Be mindful of failed injector seals. They can leak a lot of air. You may be dealing with an air leak that gets worse warm, or on air leak that really becomes evident when the need for rich fuel decreases when warm.I don't know if there's an idle bypass on these things. If there is it might be poorly adjusted. CIS is really a simple system to diagnose most of the time because fuel pressure tells you so much about what's happening to the mixture, and you can block out the aux. air system as it should have no effect on warm running.
Cheers,
Tom B.

 

Have to say (again) that this is really unacceptable, and that you shouldn't even be worrying about (or trying to fix) other modes before the warm idle is setup correctly.