triple5soul8781

car keeps throwing the code p0171
o2 sensors look to be new
ands car runs fine
just keep getting this code on
i was thinking of cleaning the map sensor?

fastrc2

no dont clean the map sensor, it cant be cleaned anyways, it just reads pressure, any ways p0171 is system too lean bank one, so that means you have either a restriction in fuel supply, or a vacuum leak. if its a restriction in fuel supply, and the engine runs smooth, [indicates injectors are at least ok] check for bad fuekl pump, low pressure pressure regulator, fuel filter restrricting the pumps outoput. if its a vcuum leak, then there is secondary air leaking into the intake tract somehow, both vacuum leak or fuel restriction is causeing the ECM tio adapt richer, and once it hits the limit of enrichment, it throws the code the engine is too lean, because its thrown all the fuel it can at it and it can see the proper feedback fromt he o2 sensor. it would be most common to have a fuel filter or a vacuum leak.

B serious

iTrader: (1)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fastrc2 &raquo;</TD></TR><TR><TD CLASS="quote">no dont clean the map sensor, it cant be cleaned anyways, it just reads pressure, any ways p0171 is system too lean bank one, so that means you have either a restriction in fuel supply, or a vacuum leak. if its a restriction in fuel supply, and the engine runs smooth, [indicates injectors are at least ok] check for bad fuekl pump, low pressure pressure regulator, fuel filter restrricting the pumps outoput. if its a vcuum leak, then there is secondary air leaking into the intake tract somehow, both vacuum leak or fuel restriction is causeing the ECM tio adapt richer, and once it hits the limit of enrichment, it throws the code the engine is too lean, because its thrown all the fuel it can at it and it can see the proper feedback fromt he o2 sensor. it would be most common to have a fuel filter or a vacuum leak.</TD></TR></TABLE>

If it's getting bad gas mileage, the 02 sensor is reading lean erroneously. That means that there really is not a lean condition. The ECU only thinks there is so it keeps adding fuel.

If there really was a lean condition, enrichment would get you back to normal amount of fuel. The fact that it's running rich enough to give him "terrible gas mileage" (OP...what type of gas mileage are we talking here?), tells me that the ECU will read lean no matter how much fuel is added and that the car is running rich in reality.

There may be an exhaust leak before the primary O2 sensor. The O2 sensor may also be faulty. If it's faulty, it may keep registering low voltage. Since in this application, the O2 sensor is really the only thing that can tell the ECU how rich or lean the engine is running, I'd start there. Is the primary O2 sensor is hanging out outside of the exhaust stream completely?

I do somewhat see what you're saying, though. The only way that could be true is to have a vacuum leak SO damn huge that all the fuel that the injectors and ECU can add is not enough. That's a pretty damn huge vacuum leak seeing as how the injectors are capable of running the car rich at full throttle opening.

The op, however, hasn't mentioned the type of car, mods, etc etc.

triple5soul8781

its a 1.6l non vtec d series (im a little new ot hondas here lol) civic dx no mods at all

i wanna say that i filled up and ive gotten a little over 200 miles so far and i might have a quarter tank left at most
although for the better part of it i was driving pretty aggressive, just trying out the car
so im wondering if that could be part of my low mpg's

triple5soul8781

bump

Syndacate

The secondary O2 sensor doesn't control fuel trim, it's for emissions.

Change the primary O2 sensor, that's most likely the problem.

Don't forget what pathetic grounds you're ruling the O2 sensor out on:
"it looks new"

So? Just because it looks new, doesn't mean it is new. Mine look new too, both of them, but they're both almost a year old. There's no reason for them to "not look new."

It points to your O2 sensor, I would change that.

Or don't change, and maybe you'll get lucky enough for it to lean out enough for you to sling a rod because you're being stupid.

Check out obvious problems first.

EDIT:
PS: I initially changed mine because I had the opposite of that same CEL (too rich, bank 1) - I took the first logical step and changed 'em (found good bosch ones really cheap (new) in the market place), and guess what? CEL hasn't came back since I put 'em in.

Of course in putting 'em in I tore the wire a bit and it grounded out to the chassis causing a complete failure of the alternator, VSS, and oxygen sensor heaters..but that's a different story .

triple5soul8781

ill swing by autozone tommorow

primary o2 sensor is the one located on top of the exhaust manifold?

triple5soul8781

bump i have a small crack on m exhaust manifold right above the primary o2...im going to jb weld it to see if it holds up but i just ordered a header tonight

hoping this is a solution

nub

Dont bother with the JB on the manifold. Might as well put BBQ sauce on it, it'll smell better. That **** wont seal on a hot manifold. I'd replace the mani. first then clear code and drive before doing the o2. That crack will let air in leading to a lean condition reading so fix the obvios first.

triple5soul8781

bump
i have ebay headers coming in the mail still

but i went to autozone and picked up an o2 sensor for the hell of it and it seems ot be running better, no more cold start bogging etc