Tuesday, October 25, 2011

Fiat Punto 75 idle problem fix

I have recently bought a Fiat Punto 75 elx. The car is 16 years old, and when you buy a car this old and cheap… let me just tell you that quality comes with a price.
Recently the engine began to shutdown at low RPM. Whenever I had to stop the car at a STOP sign, traffic lights or when arriving at a roundabout, the ignition lights would come up and the car would shutdown. This is really frustrating, especially if you have to make low speed maneuvers.

Two trips to a car mechanic and 130€ later, the problem persisted and manager was telling me the problem was probably related with the injectors, and cleaning and tuning them would cost me almost as much as the car itself.
However, one of the mechanics at the shop asked me what was the status on the car. We chatted for a while and he told me something like this: "It is my belief the problem is related to the idle air control valve".
This statement remained on my mind, so I had to make a decision, either sell the car to someone who would fix it later on, or, I could try to fix it myself. I felt an obligation to at least try and learn a little bit more about cars by fixing my own.

After some research on Idle Air Control valves, I found descriptions of symptoms that I could relate to with my car:
- Low idle RPM (lower than usual; in my case, RPM would stay as low as 700-800 RPM when it used to be at 1100RPM);
- Engine shuts down at low RPM (what I noticed later on was that it was shutting down at low speed and when my foot was off the acceleration/gas pedal);
- It was difficult to start the engine (I could only do it by pushing the gas pedal even further).
- When releasing the gas pedal, sometimes the RPM gauge dropped to 600RPM and then goes up again to 800RPM.

So, here is what I did (special thanks to everybody exchanging info on car repairs through the internet):

1. Open up the hood of the car;

2. Remove the bolts (red circle), the clamps (blue circle) and disconnect the small hose (green circle; it was enough for me to set aside the air filter assembly and gain access to the throttle body located beneath);

3. On the right side of the throttle body you have the Idle Air Control valve (or IAC; circle in red). Remove it with a Torx key. Clean it up with a carburetor cleaner spray such as STP carb cleaner. After cleaning the valve, clean the throttle body hole where the valve fits. Clean it really well (use a tooth brush and a cloth) until you remove all the dirt. Also, take the opportunity to clean the big butterfly valve on the throttle body. Afterwards assembly everything back again. There are videos on YouTube that explain you what you have to do.

As soon as I started the car... it was like I had just replaced the whole engine... a clean startup. The throttle remained at 1100 RPM, very stable.
It has been 2 weeks, over 500km and the car has given me no further problems.