Fuel Trims a2 1.4i AUA

C

carfan

Member
Hello from Bulgaria.Sorry for my bad english.I really like this forum and now i have a problem.
The problem in wife s car is high fuel consumption in city driving.The consumption is 22 mpg.Is this normal for small size car?I think that 28-30mpg is ok?
No fault codes on VCDS,runs good.On group 32 on engine management is shown STFT and LTFT and both are 0.This is not normal i guess
Thank you
 
carfan said:
Hello from Bulgaria.Sorry for my bad english.I really like this forum and now i have a problem.
The problem in wife s car is high fuel consumption in city driving.The consumption is 22 mpg.Is this normal for small size car?I think that 28-30mpg is ok?
No fault codes on VCDS,runs good.On group 32 on engine management is shown STFT and LTFT and both are 0.This is not normal i guess
Thank you
Click to expand...


Your English is good.

That is really bad fuel figures.

Have you noticed any fuel smells around the vehicle, it almost sounds like you have a fuel leak?

Steve B
 
No fuel smells around the car.No leaks.Car starts and runs good,idle is good.Only trouble is fuel consumption.
Is normal trims on 32 group always to show 0?
 
carfan said:
No fuel smells around the car.No leaks.Car starts and runs good,idle is good.Only trouble is fuel consumption.
Is normal trims on 32 group always to show 0?
Click to expand...

Not sure of the fuel trim measures.

Has the air filter been changed recently.

If so then I would replace the temperature sender, not very expensive and a "Do It Yourself" job.

There are two circuits in them, one for the Temperature gauge and one that tells the ECU what temperature the engine is at and if it is not getting the correct temperature it could be over fueling the car.

Worth trying.

Steve B
 
All filters and engine oil was changed month ago.I wil check temp sensor.im doing all car maintenance myself.One thing i want to check is timin belts alignment.
 
carfan said:
All filters and engine oil was changed month ago.I wil check temp sensor.im doing all car maintenance myself.One thing i want to check is timing belts alignment.
Click to expand...


I wouldn't waste that time to check the Cambelt alignment, you say the car runs well and it certainly wouldn't if it was a tooth out, the drop in power would be very noticeable.

If you can access a VCDS cable and software (as it sounds like you can) then you can get the readings of both temperature circuits on the sender via that.

Steve B
 
Not power drop at all but acceleration pedal response is not so good.I have a vcds and will check temp sensor circuits
 
I did some measurements and see that temp sensor circuits show close readings.Another thing i see is group 33 on engine management.Pre cat o2 sensor voltage stay 0.434V almost all the time.Not changing too much when increase the rpms,maximum about 0,500V.I think that wideband sensor must have 0-5v range??
 
Hi carfan.
Change the ecu temp sender. I had the same problem with poor fuel consumption but showing no em lights. The temp sensor works two different ways - eg thermostat to dash, which will show temp is running correctly, and thermostat to ecu which is a different switch in the same sensor. Thus the water temp is correct and sensor sends info to dash temp gauge, but not sending same info to ecu thus running as if still cold.
 
Almost sounds like a lazy lambna sesnor but i'm not so sur; The voltage should be switching quickly and your fuel trims should not read 0 (I mean, they should, but never do) which would sugest to me the car isn't going into closed loop operation, this could well be because of the temperature sensor so make sure your ECU is getting the correct engine temp signal.

(VCDS should be able to tell you if the engine management is in 'OPEN LOOP' or 'CLOSED LOOP' operation, which if there are no faults the engine management, this should be achived once the engine is up to temperature)
 
Yes car definetly is in open loop mode and maybe ignore the O2 sensor readings.Im think first to change the temp sensor with new one and check lambda sensor readings.Thanks all of you
 
i replaced the temp sensor and now testing,but now im have another big problem.Low oil presure light on dash when engine is warm up.Replaced the oil pressure switch with no success
No changhe of engine sound but i m worry about it.I replaced the oil and filter about 600 miles ago.Motul xcess 5W40.:mad:
 
I would get a pressure gauge into where the oil pressure switch is currently so you can see what is going on, low oil pressure is an engine killer and needs sorting out very quickly
 
Oil pressure warnigs was from low charghing in low rpm's.I replaced the alternator with another one with new Voltage regulator but same thing.In idle when car is warm up no charghing.When increase rpm to 1000 chrghed fine.In conector plug have two wires blue and brown.On blue one have a 6V in engine turned on.On brown nothing happened.Battery is new.alternator is replaced,what other can i look.For fuell trims again nothing both 0 on group 32.When turn ignition on on group 33 have a 8V voltage,then when start car it decreases to 0.434V and stay there.When i unplug the O2 sensor i have a same reading in gorup 33voltage,but i have a trouble codes no signal and heating error.Is it possible lazy lambda not show error codes in ECU?is any other think that affect fuel trims?Can it be from map sensors temperature readings?
 
Hello guys, can you help with this fuel trim values? I really can get that idle stay on the right rpm----no matter what i do it goes to around 670-700 after warming. The car starts very good, on the first atempt, changed the O2 sensor, MAP, EGR, spark plugs, coils, cleaned the throttle body with no help. The car is stalling when you try to drive it. Can it be a vacuum leak ? I can hear a false air sucked in when pressing the gas pedal
 

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I've noticed that when I disconnect the MAP the idle will move to the right value around 800, but it will last a day or to. After that it will go down to the first value. I forgot to mention that I've changed also the thermostat and the water temp sensor. I'm totally puzzled.
 
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