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  #1  
Old 10-10-2011, 12:57 AM
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2002 Volvo S40
 
Join Date: Jun 2011
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Unhappy P0171 code lean bank one but eating gas?

ok first ive checked all vacuum lines I.E. intake and the ones off the turbo no leaks most shops say diffrent fixes and volvo dealer wants 200+ just to hook it up to their computer this started after a fuel system clean from ez-lube and one mechanic says fuel pressure regulator diafram probaly cracked or shattered and would cause the bad gas mileage if im using more fuel why "lean bank 1" code im at the end of my rope p.s. i did replace both O2 sensors also (other mec's suggestion) please help anybody had this problem before?
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  #2  
Old 10-13-2011, 06:21 PM
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I'm thinking your bad gas mileage is because the ECM is trying to add fuel to compensate for the "Lean Bank 1". A couple of things come to mind.

On my 2001 there is a wiring problem with the upper O2 sensor wiring harness. The wires are in the wrong order on the car side of the O2 wiring harness. The fix is an adapter cable that goes between the car side harness and the O2 sensor harness that aligns the wires correctly. Does you car have that harness installed? It would be easy for someone to remove it if they don't know what it's there to do.

Also, is it possible that the upper and lower O2 harnesses were switched? I'm not sure it's even possible but if so then the cat converter would be generating oxygen which would show as lean to the switched O2 sensors (i.e. what should be the top one is actually the bottom one).

A bad fuel pressure regulator shows itself on the 1.9L engine as really long cranking times until it finally starts.
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Old 08-18-2012, 07:50 PM
Jak Jak is offline
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Hudini --
I have a P0170 Too Lean Bank 1 reading from an emissions test (in MD). How do you check the O2 sensors? Should I check for the harness problem first? If you have any pics that would be great.
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Old 08-19-2012, 02:03 PM
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Ok, what I should have asked first above is "Have you had any engine work done recently?" This because the factors I presented are not something that appear without a reason. Someone would have to remove the harness or swap the O2 sensors. I can tell you the code is set because the ECM cannot add enough fuel to make the top O2 sensor swing back to rich. Does your exhaust smell rich? If yes then I'd guess bad O2 sensor. If not then I would try to verify the car is actually lean as this can be a very bad issue. Lean engines melt things that shouldn't melt. A glowing red exhaust manifold is a symptom of a lean engine. I would check fuel pressure and replace the fuel filter if it hasn't been replaced in a while.
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2005 S40 T5 AWD

You can have it done QUICKLY, done INEXPENSIVELY, done CORRECTLY. Pick any two.
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Old 12-30-2013, 06:40 PM
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Quote:
Originally Posted by Hudini View Post
Ok, what I should have asked first above is "Have you had any engine work done recently?" This because the factors I presented are not something that appear without a reason. Someone would have to remove the harness or swap the O2 sensors. I can tell you the code is set because the ECM cannot add enough fuel to make the top O2 sensor swing back to rich. Does your exhaust smell rich? If yes then I'd guess bad O2 sensor. If not then I would try to verify the car is actually lean as this can be a very bad issue. Lean engines melt things that shouldn't melt. A glowing red exhaust manifold is a symptom of a lean engine. I would check fuel pressure and replace the fuel filter if it hasn't been replaced in a while.
Hey, i have the same code on my 2005 s40 2.4i - it comes and goes though. it has been cleared once. car passed emissions. then the same day i got the light.. the car is consuming gas like crazy though. like a v8 would.

how do i know if the exhaust smells rich? what kind of smell would this be? i bought a fuel injector cleaner to see if that cures the problem.. should i bother using that on a full gas tank?
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Old 12-30-2013, 07:36 PM
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It's hard to describe a smell. Rich is unburned fuel exiting along with the burned fuel. It is a strong smell so you will notice it easily. You may notice a black color to the exhaust.

Do you know how to read spark plugs? The plug on the left is fouled from being too rich. See the black? Too rich leaves a black powder. (Oil leaves an oily sticky black residue)



Poor gas mileage and the trouble code says too lean? My first guess is a bad top O2 sensor (bank 1). If this has gone bad it will report as lean to the ECM and never move toward rich as the ECM adds fuel. It would explain your excessive fuel use.
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You can have it done QUICKLY, done INEXPENSIVELY, done CORRECTLY. Pick any two.
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Old 01-01-2014, 06:53 PM
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ok in that case my exhaust doesn't smell rich. which vacuum lines should i check to see if anything is loose or leaking? and is the MAF easily removable? are the spark plugs easy to remove if I have a ratchet set?
also - how would I know if the fuel pump is the culprit? my check engine light comes and goes between starts.

thanks in advance Hudini! happy 2014
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Old 01-05-2014, 12:18 AM
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Happy New Year! Ok, there is a large hose near the throttle body that sometimes breaks causing weird issues. It's about 3/4" diameter and tends to break completely in two.

It's the S shaped hose that comes from the throttle body and ties into the intercooler on the right side of the red square in the pic:
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1976 240 DL
1986 240 GL
2001 S40 1.9T
2005 S40 T5 AWD

You can have it done QUICKLY, done INEXPENSIVELY, done CORRECTLY. Pick any two.
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Old 01-05-2014, 12:18 AM
 
 
 
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2002, bank, code, codes, engine, fuelsystemleanbutbadgasmileage, gas, lean, mileage, p0171, po171, poor, s40, system, volvo, whine


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