Hi Guys,

Recently bought an MK3 fiat punto grande 1.4L petrol non-turbo and really liking it so far!

There is one issue I have noticed daily which is cold-starting or starting in general where the car will start up fine, but reaches resting revs and then cuts out a few times (feels electronically controlled through ECU, not an engine failure, battery/alternator as had these issues before on other cars)

Took it to the garage and diagnostic gave faulty temperature sensor reading. The temperature sensor was replaced and the problem is still there, hopefully this may improve with time?

The garage said to do an ECU reset but I am tempted first to adjust ever so slightly the idle revs. Does anyone know where the screw to adjust this and if it is a good idea on this car? Was planning to just experiment a little and see if any difference, thanks in advance

Hi Mate,

not sure you'll find a screw to adjust the resting revs: ECU cars are (more likely) injection type, with controlled butterfly thru "fly by wire" style command.

In short, a (actually two) potentiometer hooked to the pedal informs the ECU about the accelerator position, the ECU then send the throttle body the butterfly requested position. The throttle electric motor gears the butterly where it should be, and the actual position is recorded by a (two ?) potentiometer and fed back to the ECU (or maybe internally controlled as in a servo-motor ?).

Since you engine stalls only when cold, I guess the butterfly's rest position is ok, so the problem should be with the mixture ratio: as already explained many times, the mixture needs to be enriched when engine (and weather) is cold in order to compensate for vaporisation characteristics and petrol liquid deposits on cold engine walls... Obviously if the temperature parameters are not correctly transmitted to the ECU, it can't compute a correct mixture (in relation with real parameters) and the engine stalls after a few turns...

My recommendation is to actually READ what the ECU sees from the temperature and position sensors and act accordingly.

BRs, Bernie

If someone here helped You fix -or better, understand- your issue, hit the thanks icon @ bottom right corner, it's free and makes us feel helpy ;-)

Idle air comes (most of it) from the PositiveCrankcaseVentilation system (breather hoses and orifices). Small hose is bypassing the throttle. Rest is the ECU's job (how much fuel to inject - based on multiple sensors data).

As Bernie said. Get MES/FES program (+diagnostic interface, like ELM327) and read all other parameters live.
Various temperatures, pressures, positions, lambda (oxygen sensor) readings etc.

PS
Car is recently bought? So you have a basic maintenance to do.
Some fluids (engine oil, brake fluid), filters, check the sparkplugs condition an so on.
Plus valve lash/clearances (shims) check, if it's 8-valve engine - almost no one does that.
Fuel pressure maybe. Things like that (see the Guides section).

Thank you both for your advice!

Have done a very basic service, but after quarantine is lifted planning to drive it to family home and have a full weekend checking all connections and typical things which can fail on a punto grande. The car has only done 36k miles, so will definitely need a proper maintenance, cheers

Sounds like the problem we had with my wife's car which was the MAP/air temp sensor. Not very expensive and easy to change.
Do you know which temp sensor the garage changed as if it was the coolant temp sensor then maybe they changed the wrong one.