Maf On 2.3 Petrol

[mikej]

Spooky wife arrives home from work and tells me her ultra reliable 2001 pug hdi feels rough, never broken down, traced to duff maf by simply disconnecting it while running and car ran great so now on order. Gets in the old Gal to take dog out and my bloody managment light is on, checks code P0172 fuel trim bank 1 rich ? Anyhow This is what was stored:

 

fuel system status,closed loop control using oxygen sensor-normal

coolant temp 77 deg's c

short term fuel trim bank 1 8.59% lean(-)

long term fuel trim bank 1 28.9% lean(-)

engine speed 867 rpm

vehicle speed 0 mph

 

Can anyone explain to me what a fuel trim is, short and long term etc. I have been told the maf can also cause this, is there anyway of checking a maf with a code reader if so what is the best way to confirm or any help at all would be good. Car is a 2001 petrol and runs ok but maybe with a slight hint of a misfire.

Has anybody ever changed a maf on a petrol due to this issue ? When i disconnect the maf the car runs like a bag of nails...

[Mirez]

Fuel trim is where the ECU fine tunes the running of the engine - when its doing short term its shortening the length of time the injectors are spraying petrol and long term is (obviously) where is lengthens it.

 

I can't help with the other questions but for the FT function to work correctly the ECU needs 5 vital signals. Coolent Temperature, Engine Speed, Throttle Position, HEGO (Lambda) and MAF. Of those the HEGO sensor is probably the most likely to fail (age).