Polo Fault code p0172

[martin77]

Hi,

My Polo is a 2006 1.2 and runs unevenly at tickover and the engine engine light comes on sometimes. Checking the fault codes provided P0172 Fuel trim system too rich bank 1.
Have replaced plugs and fuel filter and added fuel system cleaner. This seems to have improved things but not eliminated the problem. New filter has the pressure control integral to the filter. It was stamped at 3.0bar. Does anyone know whether this pressure rating is correct for my vehicle? Is there anything else to check?

Thanks

Martin

[davebarrans]

Hi Martin

Try the coolant temperature sensor, they don't always throw a fault code as the ecu is still getting a signal, except its telling the ecu its colder than it is and puts more fuel into the engine. Is it using more fuel too?

You can check the coolant temp in vagcom (my old polo was reading -30 in the morning when it was about 10).

don't know about the pressure control tho.

Dave

[martin77]

Hi Dave,

Thanks for note. Water temp gauge works okay. Does the ecu get it's signal from a different sensor. What is vagcom?

Cheers
Martin

[peterpaulogrady]

a bank 1 normally is the oxygen sensor on the front of the exhaust just after the manifold.ther sensor tell the ecu how much fuel is going out the exhaust so the ecu can adjust the mix.if the ecu is not getting a reading from the sensor it will automatically increase fuel

[davebarrans]

Just been reading a bit on your fault code, sorry went charging in the other day. Does it run fine the rest of the time? when was your air filter last changed?

[martin77]

Hi,

Have diagnosed problem using compression tester. Low pressure on number 3. Removed cylinder head and exhaust valve is burnt and damaged. Head now at machine shop for repair.
Thanks for posts.
Martin

[peterpaulogrady]

skimming the head wont fix the fuel mix.i would go for a second opinion if i was you.the car is a bit young for a skim to be done. the sensor measures the gases coming out of the exhaust,if that is broke the ecu cant make the proper adjustments to the fuel mix so you could end up having other problems as well. any time any sensor or egr valve stops working replace the straight away,you'll save a fortune on fuel

[martin77]

Hi,

thanks for your post but I think you missed the part where I noted that the exhaust valve is burnt and damaged. This is tha cause of the missfire and apparantly is quite common on these engines.
Regards
Martin

[peterpaulogrady]

hi,the valve burning out might be giving the ecu incorrect information. the fault code P0172 Fuel trim system too rich bank 1 usually means that the sensor on the exhaust is not working.when you get the car back clear all the codes off and bring it for a spin.if the chack light comes back on and you get the same code,it's definitly that sensor.the lambada sensor measures what air/fuel is coming out your exhaust and the ecu then corrects the mix.if the car starts to drink fuel the ecu has no way of knowing if the sensor is broke and cant make any adjustments to the mix. some times the ecu wont make any changes to the mix and you might get away with for a while but if the check light comes back on you would better off replacing it

[Bepto]

My wifes car gives the same fault code P0172 Fuel Trim Bank1 system too rich. - symptoms are irregular idling, kangarooing and loss of power. Not sure where to start, can anyone give advice please?