P0171 code fix

[thebigkahuna96]

I recently bought an 02 with the 4 cylinder 2.3l motor, and 107k miles. I put around 400 miles on it since I bought it and I had a check engine light come on last night and the code P0171 popped up on my scanner, and I’m curious if anyone else has had this happen to them and what fixed it, this is after I replaced fuel filter no check engine light was on before. Recently replaced air filter and inline fuel filter, along with a cracked coolant reservoir I replaced and fresh coolant. I think I primed fuel system back pretty good but who knows. Any help would be greatly appreciated. My scanner said O2 sensor was the most likely fix, as well as an engine intake manifold runner vacuum actuator

 

[sgtsandman]

I would look at cleaning the mass air flow sensor and seeing if there is any vacuum leaks first. If those come up as nothing, then I would look at changing the MAF first before looking at the O2 sensor. While an O2 sensor does have an expected useful life to them, go after the more common things first and eliminate them as a possibility.

OBD-II DTC: P0171 System Too Lean (Bank 1)

 

[pjtoledo]

pull the plugs to check for oil fouling. at least that's cheap.
if the intake manifold flapper shaft is leaking air will be introduced after the throttle body.

 

[thebigkahuna96]

I would look at cleaning the mass air flow sensor and seeing if there is any vacuum leaks first. If those come up as nothing, then I would look at changing the MAF first before looking at the O2 sensor. While an O2 sensor does have an expected useful life to them, go after the more common things first and eliminate them as a possibility.

OBD-II DTC: P0171 System Too Lean (Bank 1)

What all do I look at to check for vacuum leaks?

 

[rumblecloud]

Vac leaks can be hard to pinpoint - or can be easy if someone forgot to put a hose back on after performing some underhood service...

With the engine running you can listen in and around the engine compartment for any hissing sound. I've never found this helpful cuz I can't hear well and the engine running makes it worse for me, but others have found this useful.

Best way is to do a smoke test. You can buy a smoke machine or you can make a simple one. There's lots of info here in TRS on this subject.

Cope 171 (and 172) are fairly common and can be a real biatch to eliminate. Hopefully yours will be a simple MAF clean-up as @sgtsandman has suggested.

Please keep us updates on your porgress.

 

[sgtsandman]

What all do I look at to check for vacuum leaks?

Look at all the hoses leading to and from the intake maniold. Look at both ends, not just the intake manifold side. Is one missing and just hanging there? Do any of them have cracks or splits in them? Disconnect the hoses and look at the under side of them.

If all that looks good, spray brake cleaner around the intake manifold. If there is a leak in a gasket, the engine will rev up from sucking in brake fluid.

 

[Jazzer]

You could also use a propane torch, on but not lit, and aim the nozzle around all vacuum connections and manifolds.

 

[thebigkahuna96]

Vac leaks can be hard to pinpoint - or can be easy if someone forgot to put a hose back on after performing some underhood service...

With the engine running you can listen in and around the engine compartment for any hissing sound. I've never found this helpful cuz I can't hear well and the engine running makes it worse for me, but others have found this useful.

Best way is to do a smoke test. You can buy a smoke machine or you can make a simple one. There's lots of info here in TRS on this subject.

Cope 171 (and 172) are fairly common and can be a real biatch to eliminate. Hopefully yours will be a simple MAF clean-up as @sgtsandman has suggested.

Please keep us updates on your porgress.

Vac leaks can be hard to pinpoint - or can be easy if someone forgot to put a hose back on after performing some underhood service...

With the engine running you can listen in and around the engine compartment for any hissing sound. I've never found this helpful cuz I can't hear well and the engine running makes it worse for me, but others have found this useful.

Best way is to do a smoke test. You can buy a smoke machine or you can make a simple one. There's lots of info here in TRS on this subject.

Cope 171 (and 172) are fairly common and can be a real biatch to eliminate. Hopefully yours will be a simple MAF clean-up as @sgtsandman has suggested.

Please keep us updates on your porgress.

Alright guys, I cleared the code last night at work and it drive home fine this morning, which it has been driving fine I haven’t noticed any difference since the check engine light came on. After I got in it to come to work this afternoon it was on, wasn’t on this morning the whole drive home. So I went to O’Reilly and bought a new mass airflow sensor, installed and cleared the code. I will keep yall updated if it comes back on or not

 

[thebigkahuna96]

Alright guys, I cleared the code last night at work and it drive home fine this morning, which it has been driving fine I haven’t noticed any difference since the check engine light came on. After I got in it to come to work this afternoon it was on, wasn’t on this morning the whole drive home. So I went to O’Reilly and bought a new mass airflow sensor, installed and cleared the code. I will keep yall updated if it comes back on or not

Check engine light is back on after putting brand new airflow sensor. I think I might try O2 sensor now but which one? Upstream or down stream?

 

[Blmpkn]

Do both sensors at once. Buy quality sensors.. motorcraft or NTK.

As Ron would always say.. o2s are the only sensors that have a lifespan, expect 10 years or 100k out of them.

The timing works out.. a little over but close enough.

 

[thebigkahuna96]

Do both sensors at once. Buy quality sensors.. motorcraft or NTK.

As Ron would always say.. o2s are the only sensors that have a lifespan, expect 10 years or 100k out of them.

The timing works out.. a little over but close enough.

10-4, I think I’m gonna go with Bosch. Fingers crossed this works

 

[Mechrick]

I think I might try O2 sensor now but which one

Replacing O2 sensors for the P0171 code is probably a waste of money. Usually the sensor is just reporting what it sees.

You drove it 400 miles with no check engine light, then the light came on after you replaced the fuel/air filters. Most likely, you created an air leak. Double-check all the connections around the air box.

 

[thebigkahuna96]

Replacing O2 sensors for the P0171 code is probably a waste of money. Usually the sensor is just reporting what it sees.

You drove it 400 miles with no check engine light, then the light came on after you replaced the fuel/air filters. Most likely, you created an air leak. Double-check all the connections around the air box.

I found a hose about midway towards the air box, not in the intake and I re plugged it in, cleared code and now gonna see if that was the culprit