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Code P0171??

S

SaturnLvr

CEG'er
Joined
May 28, 2006
Messages
108
Hello all. I have a 2000 Contour with the 2.0L 4cyl automatic. I just got a check engine light coming on and I checked the code. It is this crazy P0171 code. I checked for vacuum leaks using propane and could not find any (propane is sooo much cleaner than using carb clean). My car has new plugs, wires, coil pack, timing belt/ belt tensioners, MAF sensor, engine coolant temp sensor and o2 sensors. All of these were replaced within the last 15k miles due to other problems. I have not changed the pcv valve yet...any suggestions on how to do this since it is such a tight spot?? Any suggestions on the next step to solve this code problem?? Thanks in advance!!
 
thats a System to lean, Bank No.1 code. Either you have a Vaccume leak, or your new Bank 1 O2 sensors is faulty. Im putting my money on the O2 sensor.
 
I know it is a fuel trim lean code and I checked for a vacuum leak and found none. I have a scan tool and I checked the o2 sensors. The upstream sensor seams to be working fine and the downstream o2 looks ok (senses rich immediately when propane is introduced to the system) but it is staying lean at idle averaging .25 volts when it should be averaging .45 volts. A look at some ford literature states that the P0171 fault code will not be corrected by replacing the downstream sensor. What do you think?? Change the sensor anyway, I just hate to spend the $50 and still have the code.
 
I did not check the exhaust manifold, I will have to check that first thing in the morning. Any other suggestions?
 
I crawled under there this morning and the o2 sensor is indeed connected. Any other suggestions?
 
A real time live data scan (about $100 at the shop or you can buy a Actron CP9180 for about $200) will help narrow down what the problem is but as you have not done it, below are some of the causes of P0171 code:

1) Air leaks after the MAF sensor or leaks in PCV system,
2) Exhaust leaks before or near O2 sensor
3) Fuel injector issue
4) Ran/running out of fuel, fuel pump not supplying enough fuel
5) Leaking EGR gasket
6) Dirty MAF sensor
7) Engine oil dipstick not seated properly

Check all these items carefully and fix what you find.
 
Lets see, here is where I stand with this issue.

1) No vacuum leaks found
2) I need to check for exhaust leaks
3) Fuel inj. issue: I put in a bottle of sea foam fuel inj. cleaner today
4) Fuel pump issue: I never run this car down past a 1/4 tank, possibly a weak pump though.
5) EGR: This car does not have an EGR valve this is the 4cyl VCT engine
6) Dirty MAF: I just cleaned the MAF today with CRC MAF cleaner and reset codes.
7) Dipstick not seated properly: New dipstick 6k miles ago, checked it and it is seated properly.

I cleaned the MAF today and put in a can of sea foam fuel inj. cleaner. I cleared the codes and we will see what happens. I pulled the freeze frame data from when the code was set, here is the info:

Coolant temp 184
engine rpm 1785
calculated engine load 37%
vehicle speed 40mph
Short term fuel trim 11.6%

Any thoughts??
 
SaturnLvr said:
...2) I need to check for exhaust leaks
3) Fuel inj. issue: I put in a bottle of sea foam fuel inj. cleaner today
4) Fuel pump issue: I never run this car down past a 1/4 tank, possibly a weak pump though.
....7) Dipstick not seated properly: New dipstick 6k miles ago, checked it and it is seated properly.

I cleaned the MAF today and put in a can of sea foam fuel inj. cleaner. I cleared the codes and we will see what happens. I pulled the freeze frame data from when the code was set, here is the info:

Coolant temp 184
engine rpm 1785
calculated engine load 37%
vehicle speed 40mph
Short term fuel trim 11.6%

Any thoughts??
Click to expand...
Not a whole lot from the Freeze frame other than Short Term Fuel Trim leaning lean (should be between -5 and +5 % at 40 MPH). Which explains the lean code.

Check item 2 again. Check if item 7 has a o-ring on the dipstick. Item 3 may require a real time scan (as your freeze frame does not show enough data). It could be a fuel injector problem (not necessarily dirty or if dirty, the seafoam is not doing the trick coming from the fuel tank). I presume you have changed the fuel filter in the last year or so. Change that before thinking of Item 4.
 
I agree, the freeze frame data doesn't tell me much other than the STFT. The dipstick does have an o-ring, just checked it. I still have to check for exhaust leaks, but I am waiting to see if the MAF cleaning did the trick. I will let you know if the CEL comes back on...so keep your fingers crossed.
 
O.K. so my CEL is back on...yeah!! So the MAF cleaning didn't do the trick. I checked for exhaust leaks and did not find any. My next step was to check fuel pressure. The fuel psi at idle fluctuated between 38 and 42 psi. I took the car for a road test and the fuel psi fluctuated between 38 and 42 psi under various speeds and load conditions. Under WOT the fuel psi spiked to 44psi. While on the road test I noticed that the upstream o2 sensor seemed very "lazy" staying "rich" for quite sometime while the downstream o2 sensor was actually reading "lean". So my question is this: could a lazy upstream o2 sensor cause this code??
 
I think I have found the problem. This morning when I started the car I heard a loud whistle noise that increased with the engine speed. I popped the hood and could hear the noise from below the intake manifold. I pulled slightly on the pcv valve hose and the noise increased. So I pulled the hose off and found it to be cracked all over. I replaced the hose with some heater hose to see if that fixes the problem. I checked the LTFT and STFT. LTFT is at 8.6% and the STFT is fluctuating between -1.6 and 1.6%. I hope that this has fixed my problem. I will let you know after a week of driving. BTW you guys were right all along VACUUM LEAK!!
 
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