P0171 lean fuel mixture

A2 Louis

A2OC Donor
Hi all project Doris has chucked this code up P0171 :rolleyes: if you start the car the car idles fine but if you rev her to 3000rpm and let off as she goes back to idle the needle jumps up and down to 600 rpm back to 900 rpm and does it for around 3 minutes until it stabilises itself back to 900rpm where it should be I was wondering does anyone know how to sort this issue

Thanks 👍
 

audifan

A2OC Donor
From Ross-Tech






Ross-Tech, LLC
881 Sumneytown Pike
Lansdale PA 19446, USA
Tel: +1 267 638 2300
Fax: +1 215 893 3816​




Search:










16555/P0171/000369



Contents

16555/P0171/000369 - Fuel Trim; Bank 1: System Too Lean
Possible Causes
  • Mass Air Flow Sensor (G70) defective
  • Intake System Leak(s)
Possible Solutions
  • Check Mass Air Flow Sensor (G70)
  • Check Fuel Pressure Regulation
  • Check Fuel Pump
  • Check Injectors
  • Check Intake System for Leaks
  • Check Exhaust System for Leaks
  • Check Secondary Air System for Leaks
  • Check Vacuum Pipes for Leaks
Special Notes

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A2 Louis

A2OC Donor
From Ross-Tech






Ross-Tech, LLC
881 Sumneytown Pike
Lansdale PA 19446, USA
Tel: +1 267 638 2300
Fax: +1 215 893 3816​





Search:











16555/P0171/000369



Contents

16555/P0171/000369 - Fuel Trim; Bank 1: System Too Lean
Possible Causes
  • Mass Air Flow Sensor (G70) defective
  • Intake System Leak(s)
Possible Solutions
  • Check Mass Air Flow Sensor (G70)
  • Check Fuel Pressure Regulation
  • Check Fuel Pump
  • Check Injectors
  • Check Intake System for Leaks
  • Check Exhaust System for Leaks
  • Check Secondary Air System for Leaks
  • Check Vacuum Pipes for Leaks
Special Notes

Category:





Categories

Meta

Live Phone Support














Unless otherwise noted, all content on this site is Copyright © 2000-2010 by Ross-Tech LLC. All rights reserved.
"VCDS" is a Registered Trademark of Ross-Tech, LLC.
Ross-Tech is not affiliated with the Volkswagen Group in any way.
Hi bud do you know where the mass air flow sensor is ?

Thanks
 

Robin_Cox

Member
isn't the MAF a sort of collar with an electrical connector in the big black air pipe on the left side of the engine bay in the petrol engined cars?
 

nalaver

New Member
Hi all project Doris has chucked this code up P0171 :rolleyes: if you start the car the car idles fine but if you rev her to 3000rpm and let off as she goes back to idle the needle jumps up and down to 600 rpm back to 900 rpm and does it for around 3 minutes until it stabilises itself back to 900rpm where it should be I was wondering does anyone know how to sort this issue

Thanks 👍
Hi Louis ,, not sure what engine and systems you have, hunting as you have described is normally caused by rich mixture or idle system fault ,if petrol engine only . if diesel idle trim or timing control .... Al
 

RAB

Technical Specialist 1.2 TDI
Try this from the manual

If you look at the top, the above is for Tdi's. There is also one for BAD:


but nothing for BBY's.

RAB
 

nalaver

New Member
Hi Louis , I just had a look at some pics of the engine , so firstly engine hunting is normally associated with rich mixture ,poor idle as in rough is normally lean mixture ,however the system is using a throttle controlled by motor this is sending signal back to ecu and ecu is controlling the flow.
The inputs around idle are speed from crank and cam shaft air flow (some engines use air flow meter others use map and throttle position , in this case I suspect it uses air flow meter (not 100 %) so anyway . Here goes with my sugestions 1 . disconnect egr valve and see if it makes a difference .
2 . disconnect the air intake from pcv .do not block the engine side only the side that goes to the inlet manifold . and test car . 3 clean the throttle body and using VCDS or similar do adaption . 4 check for air leaks o inlet manifold (use small amount of petrol in spray bottle ,be very careful as it can cause explosion if reaches spark) 5 check values for cam timing and crank timing over rev range . I can go but suggest you try these first.
Al
 

A2 Louis

A2OC Donor
Hi Louis , I just had a look at some pics of the engine , so firstly engine hunting is normally associated with rich mixture ,poor idle as in rough is normally lean mixture ,however the system is using a throttle controlled by motor this is sending signal back to ecu and ecu is controlling the flow.
The inputs around idle are speed from crank and cam shaft air flow (some engines use air flow meter others use map and throttle position , in this case I suspect it uses air flow meter (not 100 %) so anyway . Here goes with my sugestions 1 . disconnect egr valve and see if it makes a difference .
2 . disconnect the air intake from pcv .do not block the engine side only the side that goes to the inlet manifold . and test car . 3 clean the throttle body and using VCDS or similar do adaption . 4 check for air leaks o inlet manifold (use small amount of petrol in spray bottle ,be very careful as it can cause explosion if reaches spark) 5 check values for cam timing and crank timing over rev range . I can go but suggest you try these first.
Al
Do you have a picture showing where the EGR VALVE is located?

Thanks
 

nalaver

New Member
Hi nope , the egr is connected to the inlet manifold on the right side ,the pipe is steel and about 15 mm in diameter ,it recycles exhaust gas into the inlet ,this is only when warm at part throttle and idle (not at full throttle) it can jam open or closed ,it can give wrong signal to ecu , as the lambda probes are working I guess these would be at the end of my list .If the egr is working correctly you can hear it cycle as the sound of exhaust changes slightly .

Al
 
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