Hi, I have a Grande punto active 1.2 8v 57 plate.The car initially started to lack a little power and would cut out approaching junctions. I removed the throttle body and cleaned it and the breather pipe as a little mayo was present in the pipe (none in the engine or coolant). The car ran better but not perfect so I bought a replacement map sensor but the engine did not like this so went back to the original and the car seemed to run fine.

A few days later it cut out completely and will not start. The cam belt water pump and tensioner were replaced 10k (2 years ago) and is still tensioner so I don't think this has slipped. The fuel rail has pressure and the injectors are still squirting fine sprays of fuel. The spark plugs are all sparking with a nice bright spark, they were a little wet but I have been cranking the engine without it starting.

As in have fuel and a spark I'm not sure what to look at next. I have been wondering about the throttle body, when the ignition turns on there is a humming noise as it opens ever so slightly then after a couple of seconds it closes. If you push the accelerator pedal down fully it will open the butterfly, but it closes of its own accord, it cannot be partially opened with the pedal, also once you have pressed the pedal down fully and it has closed there is no further response from the pedal. Is this normal? Also what else could be causing the car not to start?

Thanks in advance.

Mark

Read for error codes first

Cheers I'll have to get a reader, any recommendations? The car is my son's and we had Green flag out to have a look they read the codes, I was not there but he said there were codes relating to the throttle body. I'm interested to know should the throttle body butterfly valve operate as the pedal is pushed or does the ECU control it until the engine has started? Thank you.
Mark

It's my understanding that the ECU controls the butterfly; it would for instance open it a bit to increase iddling RPM if the battery is a bit low in order to recharge it faster...

Regards, Bernie.

If someone helped you on this forum, hit the thanks button, it cost nothing...

Mark97 said:

Cheers I'll have to get a reader, any recommendations? The car is my son's and we had Green flag out to have a look they read the codes, I was not there but he said there were codes relating to the throttle body. I'm interested to know should the throttle body butterfly valve operate as the pedal is pushed or does the ECU control it until the engine has started? Thank you.
Mark

Click to expand...

Ok I'm NOT sure about the 1.2 engine (can't see right now which module is on this engine) but on any other, the intake valve is opening/closing depending on the pedal possition as long as the engine is off but the key is on.

Hi Cmos and Mark, have a look a this, the butterfly IS actuated by the ECU... See items 4 & 15

Regards, Bernie

Well of course it is!

The question was if you can control it with the pedal without starting the engine

Sorry if I was unclear but I was interested in whether the pedal gave control of the butterfly with the ignition on but without the engine being started. At the moment it seems to open a little as the ignition is turned on by itself automatically and then close after a couple of seconds but it does not respond to inputs from the pedal unless I push it to the floor, in which case it opens fully for a few seconds and then closes on its own with the pedal still full down.

I wanted to know if this was normal or a fault, if anyone has experience of this and a solution that would be great. Meanwhile I'll buy a code reader.

Thanks again

Mark

Hi, I have purchased a Torque Bluetooth one device and the pro android app for it, ithe car is currently showing no fault codes with the ignition on but the live data screen shows the throttle at 87% without my foot on the accelerator pedal. Pressing the pedal does not cause this figure to fluctuate. As I took the throttle body off to clean it could this be the cause. Is there a way to reset the throttle body or am I looking at a new one? I have tried disconnecting the battery overnight and disconnecting the battery with the ignition on but this has not helped.
Regards
Mark

that value is definitely not ok... but i cannot trust that the app is actually reading the value of that sensor. Also there are 2 sensors (each with 2 potentiometers on them) one is the throttle body and one in the accelerator pedal.
If i remember correctly with the key to ON my throttle body is at 13% and at idle around 9%.


Does the value change if you manually push the throttle valve open?


the engine might be flooded ( wet with fuel... it will not start until you remove the spark plugs and let if dry out for a few hours)
One other thing,

Aurick, thank you for the response, I am looking at the dashboard on the Torque Pro app, the throttle position seems to go to 90% when the ignition is turned on then drops back to 87%, if I press the pedal down before trying to start it, it goes down to 13%, but if I hold it down it will return to 87% by itself and will no longer respond to the pedal. Similarly if I crank the car the throttle will no longer respond to the pedal input. Seems weird that the throttle seems to be operating in reverse, cannot see any other readings for the throttle.
I did consider it may be flooded so took the plugs out overnigt, but when I replaced them and cranked it over it still did not fire.
Regards
Mark

Remove the intake, filter anything so you can physically see the throttle valve.

When you put the key to ON the valve should move a bit.. then 30-40 seconds later it will move through the range.
Just watch watch it does and see if it move smoothly.


Then again: have somebody pressing the accelerator and watch the movement of the throttle body valve.

The throttle is actuated by an electric motor driven by the ECU, one potentiometer connected to the butterly reads its position and feedback to the ECU. If the information is not "logical" the ECU will not allow the engine to start. The pedal got TWO potentiometers, kinda safety stuff : they must read the same position.
Was the engine actually flooded (wet spark plugs) ?

Regards, Bernie

Hi, when the ignition is switched on the butterfly does open a few mm then closes, it does not seem to respond readily to movements of the pedal, it occasionally will operate to the throttle being fully depressed. The plugs were a wet when removed. Is there any way of synching the throttle pedal potentiometers with the throttle body one? I am getting no faults showing?
Regards
Mark

Synch between pedal and butterfly is done by the ECU with respect to AFR, engine load, water temp, MAP reading, current engine RPM, etc.
I don't think that the throttle is driven while the engine is not running (ignition ON); the ECU MIGHT perform sort of check if the engine is not cranked just after the key is turned to ignition in order to verify the feedback, that needs to be confirmed by a petrol GP owner though !!

Regards, Bernie

Had a mechanic friend check the car over, agreed there was fuel, a spark and no codes showing checked cam and crank sensors, lambda sensors etc. Then did a compression test and found no compression in any cylinder. Checked the cam belt and had slipped a few teeth, likely culprit being the water pump that despite being replaced 2 years ago was leaking slightly and a little rough. New pump, tensioner and water pump fitted and it fired up perfectly. My son who's car it was had dodged a bullet as it does not appear that there was any other damage caused!
Thanks everyone for their help.
Regards
Mark