308 qv cold start air valve coolant thermo switch issue

I did a search on this and keep coming up with 308 2v info and I think the qv is a different setup? This is an '84 308 qv. Just recently on cold start in 70 degree weather (God bless FL) it will fast idle to 2500 rpm and stay there for a "long" time. That being 3+ min. Then finally idle down. Before it started acting up it would fast idle for 30 seconds at 2000 then idle down to 1000 and your good to go, which I think is much more normal. So is this an issue with the cold start thermo switch? Does a qv have this on the bottom of the expansion tank?

thanks
jim

 

I think the switch you are looking for is on the bottom of the expansion tank. That's where it is on my '83. I don't remember if it shorts or opens when it gets hot, but it's easy enough to play with and see.

You do have enough water in the system, right?

 

coolant level is good. I'll take a look at the bottom of the tank. For some reason I thought the qv had a slightly different system

 

1983 US 308QV and 1984 US 308QV are quite different for cold start-up operation. On a 1984 US 308QV, the coolant thermoswitch in the expansion tank has little to do with cold start-up RPM (whereas, on a 1983, it has a huge effect). I'd rule the AAV's operation as OK, or not OK, first for this symptom on a 1984.

 

Got a min to enlighten me on the '84 AAV test for good or not good? Or a link if this has already been discussed at length?

thanks
jim

 

Ok - found the test. it appears it takes the AAV a long time shut. I haven't tested to see if its getting 12v to the heating element yet. Next question is my US version its under the expansion tank, looks like a pain in the a** to get access to remove. Anyone have suggestions on removal and/or the correct part number for an 84 qv us model

thanks

 

Well, you could try a search in this 308/328 section using "testing AAV" and read those threads

First thing I would do is "pinch" one of the large rubber air lines going to the AAV closed (simulating a fully closed AAV) during the 2500 RPM cold running to see if the RPM drops significantly:

If it doesn't = problem is elsewhere.

If it does = I would then unplug the electrical connector from the AAV and measure the resistance between the two AAV terminals -- should be something fairly lowish (10s or 100s of Ohms, IIRC, not infinite Ohms. You can also measure the voltage between the two terminals in the unplugged harness connector -- it should be +12V whenever the engine is running.

Bottom line is that the sliding valve inside the AAV needs to be somewhat open when cold, and fully closed fairly soon after the internal heater has +12V applied and/or the body of the AAV has absorbed some heat from the coolant/engine.

PS You can access the SPC for '84-'85 US 308QV under "308 Quattrovalvole USA" here:

https://www.ferrariparts.co.uk/diagram/ferrari/308-quattrovalvole-usa/012-fuel-injection-system-fuel-distributors-lines

But if you do need a new, one search on the "121744" Ferrari part number here to get threads that might give the Bosch 10-digit part number to get from a less expensive source, or maybe someone who could rebuild it.

 

Thanks, yeah I found the test threads after I asked. I know, always search first, but thanks for the info

jim

 

So are you saying that you did pinch an AAV air line closed (in the cold-running time frame where it would normally already be down to 1000 RPM) and the high cold RPM dropped a lot? Please do report whatever you do eventually find/measure.

 

Yep, pinched the line and it worked like a charm. So I plan to take it out and inspect / clean it. And make sure its getting 12v.

jim

 

Hi Steve, So I took off the AAV and it appears to be working fine. I have 12v and can start the car and watch it slowly close. Takes about a min to almost fully close. When at room temp its about 1/2 open. So its operation seems normal.

 

And to clarify the above pinch and it worked fine - I took the hose loose and plugged the end, not a pinch. So no air and it idles down. But it appears with any air through the aux intake as the aav closes it does a high fast idle until the aav is completely shut.

 

So, are you saying, the AAV does full close, but it just takes a lot longer time than it used to? Is it still doing "it will fast idle to 2500 rpm and stay there for a long time"?

 

so the aav does fully close, it takes a minute or so. But it seems with almost any amount of aux air the car revs to 2500. After the aav closes or you manually close the line it idles down to 1000.

 

Sounds like your AAV has become sort of binary (open then snapping closed) rather than closing smoothly and gradually. Haven't seen any time vs temperature vs airflow spec for the AAVs in the F documentation, but your AAV's behavior seems unusual.

 

It opens and closes over the course of a min or two, its just until its fully closed the idle seems high at 2500 on a 65 degree am

jim

 

So what related on a 82 GTSi does this AAV look correct when room temperature say 15deg C ?
On cold start engine revs lower than standard ( about 800 rpm and lumpy until it warms up a bit then smooth at 1000 rpm after)
The AAV does close with the heater when voltage applied both in and out of the car over a few minutes so operation is ok and measured resistance is ok, I’ve tried to adjust the little bolt on the unit that moves in the slot but it’s over to the maximum adjustment already, and I’ve cleaned it with contact cleaner and a tiny amount of WD40 too, is it worth taking it apart? And if so how?
Thanks
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Oops meant to write somewhat not so what


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And engine running on lower than normal idle at cold seems very rich


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That amount of open area at room temperature looks quasi-reasonable to me. For your cold idle being low and lumpy (even though it should be higher with that extra air entering the engine when cold), your next diagnostic step would be to measure the cold and warm control pressures of the WUR -- both need to be OKish. Since the car gets tweaked up at whatever the warm control pressure is, even if wacky, warm running can be made to be rather OKish, but good cold-running relies on the difference between the cold and warm control pressures being in spec.

 

Hi Steve, honoured to receive your expertise as usual, forgot to mention this is after removing all the us spec pollution equipment including the cold start valve ( all connections properly done to disable it ) I’m guessing while this was on the car it may have been covering up any idling / pressure /mixture issues on the WUR ?
Could it be a simple mixture adjustment somewhere for idling? I presume if I change the idle mixture for warm up it will also affect the idle mixture during normal warm running ?
Thanks


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No, the idle mixture is adjusted during normal warm running idle (when the WUR is providing the warm control pressure). The idle mixture for warm up (i.e., during cold running) is then enriched by the WUR providing the (lower) cold control pressure. This is why both the warm control pressure and cold control pressure from the WUR need to be in spec.

 

Understood, is there a quick guide of how to read these pressures and what equipment I need to buy?


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"Quick guide"? No , but you could try looking on YouTube for videos of measuring the WUR control pressures.

The best F reference for K-Jet without Lambda is Chapter D of the Mondial 8/QV WSM 281/83 which you can get a copy here:

https://www.dropbox.com/s/z99soo68ny9n2qa/Mondial8qv_workshop_281-83.pdf?dl=0

Bosch CIS was also used on Volvo and MB of the same era so shops that deal with those can maybe be a resource for you.

 

Perfect, thanks again


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