Hi, in February my EML came on (07 Hawkeye Sti - 2.5L). Garage said diagnostics say "bank 1 mixture too lean(P0171)". Each time they did something, it ran okay for a couple of weeks then the EML comes on again, and it's always "can't fit you in this week".
It's had - New purge solenoid, Lamda sensor, numerous associated hoses, now all hoses replaced with Silicon vacuum hoses. Same diagnostics again and again, roughly 7/8 visits.
Lost confidence in that garage, only been able to drive 1000 miles since february. EML came on again Tuesday.
I have had the car nearly 6 years and always used Shell V power or Tesco Super unleaded (more often).
Booked into a different garage this morning. Ignition on , engine not running. Diagnostics - bank one too lean, suggested I stop using Tesco petrol. Said he couldn't reset the fault, suggested going to an Auto electricians, unplugged the Diagnostics. Started the car, EML went off. Drove 2 miles , while waiting at a junction the revs started to fluctuate between 500-1000 revs and felt as if it was about to cut out. EML came back on. Auto-electrician can't fit me in for 10 days.
In the meantime I thought I would see if anyone else has had anything similar, and what the fix is. Only other info that may be relevant - had an engine refresh last August, but car ran fine on mostly Tesco Super unleaded petrol from August to Feb.
Any suggestions?


Thanks in advance.

 

Assume Tesco Super unleaded is actually Tesco Momentum (99Ron) ?
Diagnostics for P0171- "Lean" are the same as P0172 - "Rich"

MY07 P0171-2 pdf

Check for exhaust and air inlet leaks
Clean your maf
Maybe time for a fuel filter change (in fuel tank alongside pump iitem 13 below)


http://opposedforces.com/parts/impre...llustration_2/

 

Hi Don, thanks for that. It is the Tesco momentum as you mentioned. It was tested for air leaks at the first visit and found to a have a crack in the purge solenoid, which was replaced. Mechanic told me that he had checked and cleaned the other bits, but EML stayed on. Only when they replaced the Lamda sensor the EML went off. Later tests highlighted the associated hoses.
I will look into the fuel filter, but I would have thought that would effect both banks. It is only ever bank 1 that is effected.


Cheers

 

What brand of 02 sensor was used ?

 

Hi JDM Stig, doesn't say what brand it was on the bill ,but the part No. is FPSVE381422. Whether that is an OEM or suppliers number, I don't know.
Cheers.
P.S. It was £250 , so I would hope its an OEM.

 

Typically OE is Denso, and seem to be cheaper than what you paid for what looks like a brand called Cambiare, they use a PN that is very similar and that is for a Impreza.
https://www.ebay.es/itm/Sonda-lambda...m4383.l4275.c1

 

Bank 1 refers to the sensor (you only have one A/F sensor) not the cylinders.

 

My P0171 was due to exhaust leak - one of the gaskets on the bit of exhaust manifold pipe which runs from left to right sides of the engine was blowing.