Hard to start cold but then runs perfect. 1.8 20vt aqx engine

[Giannakos]

Hello everyone.
I have a mk3 Ibiza 20vt. About six months ago a problem started to occur at my car. When the car is cold it takes about 10 seconds to get it running. If you turn it off and then start it again it turn on in half a second. Does anyone come up with this issue? Any help will be much appreciated.
I have changed the coolant temp sensor. Fuel regulator valve, spark plugs, pump relays.fuel filter.
Vag com doesnt show any fault codes.
About the time it started the problem i had replaced the crank sensor with an oem one. Is there a possibility that it could be faulty?
Thanks a lot in advance.

 

[Cupra999]

I think that this is a bug in the software of the car, the map in cold weather should send more fuel in cold start, some one can correct me if I'm wrong?

Your fuel pump might be weak too, try to connect to vag com to see if the fuel trim blocks: short and long fuel trim are adding fuel ( positive %) when you accelerating in full throttle, be careful, do a record of the trim or ask a friend to watch it, is it adding fuel you have weak pump, if only the short fuel trim block adding fuel your pump is not so weak.

If the pump is weak, Not sure that changing the pump will element the problem but it should make it better

 

[Cupra999]

More thing to try is to get from AliExpress or any other place a fuel regulator that has option to change the fuel pressure, try first to calibrate it to 3bar or check that it's calibrate to 3bar, before installing it, there is need to see the fuel trim blocks on idle, write them, install the variable fuel regulator and check that fuel trim is the same, if not calibrate it to be the same % as was the OEM regulator and that will be your 3bar reference in the variable regulator, make a mark on the regulator for this point.

Now need to move the regular a little up, let's say to 3.3bar, that should be when the short trim is 10% LESS than what it was at idle with the 3bar OEM regulator, because now the pressure is 10% more and the computer subtract 10%. The computer compensate for that.
Like that it's possible to prove that it's indeed lack of fuel, if it fix the cold start

 

[Giannakos]

More thing to try is to get from AliExpress or any other place a fuel regulator that has option to change the fuel pressure, try first to calibrate it to 3bar or check that it's calibrate to 3bar, before installing it, there is need to see the fuel trim blocks on idle, write them, install the variable fuel regulator and check that fuel trim is the same, if not calibrate it to be the same % as was the OEM regulator and that will be your 3bar reference in the variable regulator, make a mark on the regulator for this point.

Now need to move the regular a little up, let's say to 3.3bar, that should be when the short trim is 10% LESS than what it was at idle with the 3bar OEM regulator, because now the pressure is 10% more and the computer subtract 10%. The computer compensate for that.
Like that it's possible to prove that it's indeed lack of fuel, if it fix the cold start

Thank you very much for your reply. Due to my need for towing boats i sold the car without figuring out the problem. Thanks for your reply though.

 

[Cupra999]

No problem