Alfa 75 running fault.

[simmi1983]

Hey,

I finished my 75 TS racecar and took it for practice on Sunday. Was very happy with how it went-handled , broke and went well. Although after 4 or so Laps when the temp started to climb to 100 (too hot I know ) I began experiencing a cutting out sensation at around 5000 rpm, as though I was hitting a rev limiter-it wasnt there on the first few laps,and in the next session it did the same thing-ran like a dream all the way to 7000rpn and then as the temp started to climb it would come back.
I took into pits and popped the hood -hoses where very hot but no bubbling or spitting out the overflow.

  Now there is no doubt it is running too hot and will look at the cooling system(check the thermostat, have radiator flow tested and block of the heater lines as the heater has been removed and I mistakingly looped them rather than blocked off.
But my question is this.. do these things behave like this when they run warm or am I looking for another fault. It just seems too coincidental to me that it would develop with the heat, or am I looking at 2 faults?

I am thinking its to do with the heat but what could do that? 
Maybe CAS is getting too hot and wigging out or it just that the cylinders are to hot to burn efficiently?

I am ruling out the fuel cell as it absolutely hauled arse for 4 laps before it got warm, I am also ruling out coils and distributors as it us highly unlikely they woyld both play up simultaneously.  All I can think is too hot ir crank angle sensor.

Would love to know if anyone has had this same experience and would like to hear some ideas as I am taking it to the track again next weekend.

Cheers,

Luke.

[bonno]

Hi Simmi
I would sought the overheating problem out first. Could be a simple fix such as a faulty thermostat. If not, you might need to look further into the cooling system such as fit additional fan,  larger radiator, etc.   A useful tip with an overheating problem and involves checking the correct operation of thermostat. This method allows it to be checked without pulling apart thermostat housing and checking it in boiling water. It uses the squeeze method of the radiator hose once engine is hot refer Method # 3. Refer to the following link for details : 
http://www.wikihow.com/Tell-if-Your-Car%27s-Thermostat-Is-Stuck-Closed

Regards
bonno

[Duk]

The CAS isn't going to suffer because the engine is a bit warm.

Without being able to see the maps, maybe the engineers created a safety mode in the ECU by adding fuel and retarding ignition timing if the engine started to get too hot (it's easy enough to do). Ford did similar in their ECUs.
A wide band air/fuel ratio meter would show any over fueling as a result. Ignition timing changes (retarding the ignition timing) would be mutch harder to see directly. But an exhaust gas temperature sensor should show some increases in temperature as a result of retarded ignition timing.

Look at all of your ignition leads and spark plugs to make sure that they are to correct spec.

Perhaps a ambient temperature based fuel pump problem???  Monitoring fuel pressure when the engine is misbehaving would reveal a dud fuel pump.

And fix your cooling issue.

[V AR 164]

It's a long shot, but I have recently fixed a similar missfiring issue with my 3ltr. After 6 months of trying to solve the issue, I managed to track it down to be a faulty coolant temp sensor connector. Replaced it and the car has run perfectly ever since.

I could be wrong, but would definately recommend checking out the coolant temp sensor itself and the connector with its wiring loom.

Andrew.

[simmi1983]

Hey ,

Crank sensors can cut out /stop reading when they are faulty and get too much heat into thus creating too much resistance and cause a misfire.. I see it hyundai Getz's and Navaras /pathys  all the time. Commodore is another common one but they stop running. 

I have found a couple of issues in my cooling system and will have to see how it goes. Will have a spare CAS at the track just in case.

Im still hoping that there is a program in the mapping that limits RPM when temp gets too high.

Thanks for the input guys


Cheers,

Luke

[GTVeloce]

It is unlikely to be the CAS - in the TS engine they either work or not - there doesn't seem to be a middle ground. The engine temp sensor is more likely or the AFM which also has a temp sensor in it.

[Darryl]

When you say it is unlikely to be ignition, because why would they both fail at same time - are you 100% sure both are good (including good when hot)? I've made a similar assumption and then found out that it was really running on one good (ish) and one very sad ignition system to start with...
Don't ask me exactly what it was though - I threw leads coils, rotors and caps at it...

[simmi1983]

Fair point,  Darryl. It just ran so bloody good and was so quick to drive I assumed everything was good. Rotors, plugs,caps n leads done a couple of years ago but might get it warm today and run on individually on each coil and see what she does. I capped off the heater hoses and found that the Coolant level sensor was leaking under pressure so that should be my cooling issues sorted. For the sake of $18 I chucked another CTS in it too.

Cheers

Luke