Stalling When Hot

When you said Performance was terrible does it feel like it’s running on four-cylinder before the engine dies?

 

There is a fuse box white connector, that might show some signs of burning, when the car has been off and cold things are fine, then the fuse box connection heats up under load and the connection relating the fuel pump can be affected. Check "burnt fusebox connector" on Fchat for further perspective. Get some Deoxit and clean the various connectors. Reseat some of the key relays (use deoxit on the pins), and that of the ecu connectors, sometimes just reseating creates a fresh electrical connection surface that can solve for some of these electrical glitches. These are easy and no cost checks that you need to do to rule out some simple things.

Could be a failing coil(s) taking out one bank of cylinders, the car is like to 2 four cylinder engines with two separate ignition systems and will run on 4 cylinders only, but poorly and somewhat like you describe. That's why people will ask if it feeling like it is running on one bank. It feels like you describe, the engine is still smooth, but feels down on power and won't hold the idle without some throttle.

The ignition coil failing can present intermittently. There are other causes for what you describe, like a dist cap, rotor, or crank sensor, but not that corrlelate to when running hot only.

I don't think it would be the AAR (AAV), its main effect is on cold start idle speed, if it did not close up after warm up, the idle would simply remain too high.

 

I knew you would ask that...unfortunately I am not aware of a reliable way to test the coils (there may well be one). You can clip a timing light on an easily accessed rear bank spark plug wire and see if that bank is getting spark. You can then swap the two coils and see if the rear bank still gets spark. This coil swap is how most seem to diagnose the issue.

 

On these cars many problems that seemingly present as electrical can end up being fueling related. But one would generally want to rule out electrical before going to the fueling, especially when the issue is intermittent.

My car presented like you described, but eventually would not start cold either, I removed some spark plugs and was getting plug fuel fouling, but all electrical checked out (and I had put in new coils recently), it was the fuel distributor. There are rubber parts inside that degrade with time (and modern fuels). There are fuel pressure tests that would help diagnose this, but given my fuel distributor was almost 35 years old and never been rebuilt, I just took the leap and had it rebuilt and everything was solved.

 

it's an '84, so does either of the slowdown lights come on? would indicate a bank cutting out.

 

What version? US or euro?

 

Slow down light will only come on when your catalytic is overheating. I ask if only four-cylinder is running because sometimes one of the Digiplex can go bad, which means you will lose one bank and to troubleshoot it to swap the two boxes and see if the problem transfer from one bank to another..

 

Coils on the way out tend to make the engine mis and back fire on one bank. Car will start up fine and you will go a few miles and it misses etc. when it does this compare the temps of the coils by hand- should be the same and if one is warmer, then it is breaking down. Mine would do 3 miles then bang and fart like an old banger

 

Long shot but I think there is a protection relay in the right side of the rear trunk - under the carpet, you have to un screw 4 screws, and flip the plate upside down. sounds to me either the relay is un plugged, or the fuse is gone... this happened to me in the past... it would start fine, warm up a bit and then run badly... no power and slow to revv.... hope that is it! I used electrical tape to hold the relay in place, as it would jostle around and work its self loose.... you may also want to check for air leaks in the hoses coming and going to the AAV and plenum. some of them can get dry rotted, look fine, and as they warm up, they expand and cracks let in un metered air... also check the small L shaped hose from the plenum to the cold start... it can crack as well.

 

One easy test that you can do is just unplug the coolant thermoswitch on the coolant expansion tank -- item #64 here:

https://www.ferrariparts.co.uk/diagram/ferrari/308-quattrovalvole-usa/018-cooling-system

and then connect the two wires in the harness together -- this simulates cold-running (with that coolant thermoswitch closed) where the injection system runs open-loop. If it runs "better" when warm with those wires connected together and then poorly when warm when you disconnect them (or put them back on the coolant thermoswitch) = something not right in the "with Lambda" closed-loop part of the system (like bad O2 sensor, bad FV, bad injection ECU, etc.).

Tom's point about something in the Protection Relay system being intermittent is also valid. The Frequency Valve should "buzz"/vibrate whenever the engine is running (cold or warm). Verify its behavior by touching it when you have the good-running and the bad-running.

 

I found this. It may be worth looking at the TPS connector and cables.

https://www.ferrarichat.com/forum/threads/hot-stalling.648831/

post 7

 

Have you tried some fuel injector cleaner in a 1/4 full fuel tank

 

The crank position sensors can also act up intermittently, they are magnets that degrade with time and heat. Those coils would also remain suspects.

 

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Radio power antenna?