Throttle Response

[Kern Fischer]

Hello Abarthites,

Last weekend I took my 2013 Abarth to a road racing track event. After the second session the idle was fluctuating up and down, the throttle would not respond, and I was getting the throttle indicator light. I let the car rest between sessions and took it out for the next session. While on the track it responded OK to throttle inputs but showed the indicator light and idle issues when I slowed to come into the pits.

That evening we drove it to dinner and learned that when the issue occurred I could shut it off and restart it and it would respond to throttle inputs like normal until I had to slow (under 10 MPH) or stop. Then the light would come on and it would go into what I suspect was “Limp” mode.

I chose not to do the second day sessions and try to get the car home. During the eight hour drive home the same characteristics occurred. It would run fine and respond to my throttle inputs and worked with the cruise control until I had to slow or stop. Then I would get the light and no throttle input. Turn off and restart and it would run fine until the next slowdown or stop.

I conclude that the throttle motor is probably OK as it works fine between slowdowns. I had a previous failure of the throttle motor and during that failure there was no throttle response at all. I am suspecting either the throttle position sensor or the ECU.

What thoughts does the community have?

[Fabio13]

Is your car OEM stock or modified?

[Kern Fischer]

Is your car OEM stock or modified?

The engine is totally stock with no intake or exhaust system mods.

[doverosx]

Scan the codes and tell us what they are.

Your symptoms DO demonstrate a dying battery and/or throttle body.

[Kern Fischer]

Hello Again,

I had the car scanned and the result was that there was an excess air flow or a vacuum leak.

I started the investigation to find any vacuum leaks and one item immediately stood out. Right next to the throttle body on the inlet manifold was a tube about 5/16 inch diameter that was pointed upward and rearward at about a 30 degree angle from vertical. It was open and looked like a hose should have been attached. The surface was relatively clean as if the hose was recently removed.

I looked around to find any loose hose and/or another fitting to which a hose might go and found no clue.

Can anyone help me define what that tube is for and where a hose might go from it?

For now, I have placed a short length of plugged hose on that tube to see if my problem goes away. If it does, I will know that that open tube was causing the issue, but would still like to determine what that port was for.

[Kern Fischer]

I took the car for a test drive and the issue did not return. The throttle response was also better as there was no leak of boost pressure through that port after the turbocharger. One theory is that the tube/port had a cap on it and the extended driving under boost at the track may have blown it off. Age, heat, and possible stiffening of the cap may have contributed to the failure.