No fast Idle on cold start up

What year/spec car?

 

The start up idle involves the auxilliary air valve (AAV). There is a disc inside that opens and closes based on both the coolant temperature and an electrical signal. Clean the electrical contacts on the wire plug, and you can take one hose off of it and spray some wd 40 in there, the metal disc might be sticking closed. If sticking closed this will cause the car to run too rich on cold start up, and could create some of the rough running. Does it hot start ok?

There are different AAV's for the US and non-US versions, you should post a picture of the AAV. I am pretty sure you would have the US one as that makes the idle quite high at start up for reduced emissions by getting the cat converter heated up more quickly. It attaches underneath the coolant tank. It is Ferrari part number 121744, and is only available used or you can rebuild. I think the more readily available non US type will retrofit as well, but will give a lower start up idle rpm, which may be better for the engine anyways.

There is also the warm up regulator (WUR) that may have an impact of start up idle. My late 3.2 Mondial does not have a WUR, so I am not familiar it, but there are plenty of threads on that component.

 

The AAV is item 44 in this exploded diagram...

https://www.eurospares.co.uk/parts/ferrari/328-1988/fuel-system/fuel-distributors-lines-for-us-version-38919

But the surging idle symptom can be a vacuum leak. Check all of the hoses that go to the AAV, you can see them in the exploded diagram as well. Makes sure they are not cracked and tighten up the various hose clamps. The AAV will not work correctly unless the system is sealed up.

Also check the vacuum hoses 11, 32 and the big plennum hose 29 for integrity in the follwoing diagram...

https://www.eurospares.co.uk/parts/ferrari/328-1988/engine/air-intake-and-manifolds-38921

It makes sense to rule out some of these simpler things, your hoses may well be originals and age and engine heat cycling takes a toll on rubber.

Shaking steering wheel feeling sounds like a cylinder missing, have you had spark plugs, dist cap and rotors done recently?

 

My initial thought is a vacuum leak.

As to the steering shaking, no idea.

 

4 Webers solves the problem.

 

Hello,

My primary differential for "loss of cold start fast idle" (328):

* AAV (auxiliary air valve) #121744 faulty - located beneath the coolant tank on your 1988; can test by removing and inspecting degree of closure (some place in freezer), then applying power and ensure closes completely (or nearly so). In this situation one would expect to be stuck in "closed" (obstructed) position. Original can be rebuilt by Fuel Injection Corporation as the specific Bosch part number is difficult to find.
* Coolant tank sensor #121777 - located on medal side of coolant reservoir tank, this should show electrical continuity (essentially 0 ohms) when cold and discontinuity (infinite ohms) when hot. Fairly common failure item that signals the fuel injection when the engine coolant has warmed (don't recall the specific temperature value - 60C?); a practical test would be to bridge the harness connectors to simulate cold and disconnect one to simulate warm states. There is also a second temperature sensor #115562 located near the starter that controls full enrichment (as as I remember works in the inverse so not interchangeable) to signal the injection system based on engine oil temperature but I do not believe affects cold fast idle.
* Warm-up regulator (WUR/control pressure regulator) #121743 pressure stuck on "warm" - measure control fuel pressure from cold start to warm (about 2.0 bar to 3.2 bar over 4 minutes); if your control pressure is stuck at 3.2 bar (or higher) the injection system will not permit higher fuel flow when cold and essentially cause engine to run at lower RPM until warms. Test with engine running to ensure vacuum applied. As above, can be rebuilt as the originals are difficult to find and quite expensive (personally have experienced this twice).
* Also check the throttle position switch (TPS) #121517 for engagement of the "idle" position; must check electrically (or construct a jumper), I have one example that makes the metallic "click" but does not demonstrate continuity at idle.

One member previous also noted improvement with replacement of the spark plug wires, the specific mechanism for this was probably high/infinite resistance in several wires resulting in non-firing of spark plug(s). And unless hoses are "sealing" when warm, I would anticipate a vacuum leak would influence both cold and warm engine running behavior. Exhaust configuration should not affect cold fast idle speed as the system is running in "open loop" (no oxygen sensor feedback).

And I'm sure others will expand on this list with other possibilities I've overlooked.

Hope this is helpful.

 

WD40 leaves a layer of gook behind. Wouldn't carb spray or brake clean be better? As for checking vacuum leaks, a really effective method is a smoke test.

 

The disc in there is a mechanical and spring valve actuated by a bimetallic strip, with an electrical heater coil as well. You want a lubricant in there to free up the disc, as well as something that will not damage the heater. Perhaps some of the Krown rustproof type of compound that is safe for platics and electrical would be good, but WD40 is just a mineral oil in a carrier, and will loosen a stick disc so would fit the need as well.

 

Did you ever find the solution for this problem? I am having a similar issue and would love to know what you found.

Thanks

 

I park my 328 in two places. One is in the basement (underground) where the temperature is about 62 F. I also park it in a garage that has a western exposure with two other vehicles and a temperature in excess of 75 F in the summer. Upon starting a cold engine, the fast idle only occurs when I park it in the basement. There is no fast idle when parked in the warmer garage. It has been this way for years. I have been tempted to place a bag of ice on the reservoir to cool the auxiliary air valve in order to determine whether that would cause a fast idle upon starting a cold engine in the hot garage. The second part of the test would be to place a bag of ice on the WUR to see what effect that would have.

 

Have you guys tried to detach the O2 sensor and see if that makes a difference.

 

I have not tried that yet. To be honest, I don’t know this car well enough yet. I just got it. I am not even sure which models have the O2 sensor setup.

 

As an 88 you have an O2 sensor.
If you can - follow it back from the header/exhaust you can see there the end connection is and can disconnect from there. just don’t do it when the engine is hot. Trust me it hurts.




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I had the same problem: the cause was the auxiliary air valve not moving, due to some dirt in it. Clean it and check its electric connections.

It's located under the water expansion tank

Ciao

 

Temperatures cited were Fahrenheit, not Celsius. Vehicle does not run at 95 F.