Time for a smoke test - P0171 issue
11-01-2022, 03:59 PM
#21
Moderator
Join Date: 01-23-2009
Location: Fredericksburg,VA
Posts: 25,325
The purge valve should be normally closed. When testing EVAP the intake manifold doesn't get involved.
Disconnect the back connection of the valve introduce smoke to the tube, look for smoke emerging in front of the driver rear wheel well. To check the purge valve disconnect both sides blow into it, should be closed.
if the purge valve is stuck open fuel vapor will be entering the combustion all of the time, cold start can be hard. Hole in vapor line would introduce air when the purge is supposed to be all fuel vapor.
Disconnect the back connection of the valve introduce smoke to the tube, look for smoke emerging in front of the driver rear wheel well. To check the purge valve disconnect both sides blow into it, should be closed.
if the purge valve is stuck open fuel vapor will be entering the combustion all of the time, cold start can be hard. Hole in vapor line would introduce air when the purge is supposed to be all fuel vapor.
11-01-2022, 05:53 PM
#22
Senior Member
Join Date: 12-05-2014
Location: Northern Ohio
Posts: 2,623
It’s a leak after the MAF that would be a problem.
A bad O2 sensor could be lying, causing a perfectly good a/f be trimmed excessively thus throwing the code, trimmed excessively rich to be specific, causing the fuel smell.
A different possibility - didn’t at least some 2007 2.2’s have those cranky fine-orifice injectors that were prone to clogging? This would be especially suspect as the trouble began after the car was parked for awhile. Uneven a/f in different cylinder could cause hunting for a good a/f, not bad enough to cause misfire codes. A leaking injector seal could cause similar effects and fuel smell under the hood.
By now I would have had a scanner watching long and short term fuel trim while running, at startup and once warm.
A bad O2 sensor could be lying, causing a perfectly good a/f be trimmed excessively thus throwing the code, trimmed excessively rich to be specific, causing the fuel smell.
A different possibility - didn’t at least some 2007 2.2’s have those cranky fine-orifice injectors that were prone to clogging? This would be especially suspect as the trouble began after the car was parked for awhile. Uneven a/f in different cylinder could cause hunting for a good a/f, not bad enough to cause misfire codes. A leaking injector seal could cause similar effects and fuel smell under the hood.
By now I would have had a scanner watching long and short term fuel trim while running, at startup and once warm.
11-01-2022, 06:14 PM
#23
Member
Thread Starter
Join Date: 12-17-2010
Location: High Desert, CA...
Posts: 51
The purge valve should be normally closed. When testing EVAP the intake manifold doesn't get involved.
Disconnect the back connection of the valve introduce smoke to the tube, look for smoke emerging in front of the driver rear wheel well. To check the purge valve disconnect both sides blow into it, should be closed.
if the purge valve is stuck open fuel vapor will be entering the combustion all of the time, cold start can be hard. Hole in vapor line would introduce air when the purge is supposed to be all fuel vapor.
Disconnect the back connection of the valve introduce smoke to the tube, look for smoke emerging in front of the driver rear wheel well. To check the purge valve disconnect both sides blow into it, should be closed.
if the purge valve is stuck open fuel vapor will be entering the combustion all of the time, cold start can be hard. Hole in vapor line would introduce air when the purge is supposed to be all fuel vapor.
Never had hard cold or hot starts. Lights up right away.
One thing I did notice is that upon start up, it revs up high then comes down. I don't remember it doing that before.
11-01-2022, 06:31 PM
#24
Member
Thread Starter
Join Date: 12-17-2010
Location: High Desert, CA...
Posts: 51
It’s a leak after the MAF that would be a problem.
A bad O2 sensor could be lying, causing a perfectly good a/f be trimmed excessively thus throwing the code, trimmed excessively rich to be specific, causing the fuel smell.
A different possibility - didn’t at least some 2007 2.2’s have those cranky fine-orifice injectors that were prone to clogging? This would be especially suspect as the trouble began after the car was parked for awhile. Uneven a/f in different cylinder could cause hunting for a good a/f, not bad enough to cause misfire codes. A leaking injector seal could cause similar effects and fuel smell under the hood.
By now I would have had a scanner watching long and short term fuel trim while running, at startup and once warm.
A bad O2 sensor could be lying, causing a perfectly good a/f be trimmed excessively thus throwing the code, trimmed excessively rich to be specific, causing the fuel smell.
A different possibility - didn’t at least some 2007 2.2’s have those cranky fine-orifice injectors that were prone to clogging? This would be especially suspect as the trouble began after the car was parked for awhile. Uneven a/f in different cylinder could cause hunting for a good a/f, not bad enough to cause misfire codes. A leaking injector seal could cause similar effects and fuel smell under the hood.
By now I would have had a scanner watching long and short term fuel trim while running, at startup and once warm.
No issue with MAF, what I was mentioning is that when I smoke thru booster hose and I seal the end of the elbow where it connects to air box, it builds pressure but there is no smoke coming from under hood such as a bad manifold gasket or other seals so it must not be leaking from seals.
2 yrs ago I had bad O2s and I switched them out with some Denso's and I have been hearing some bad things about Denso and was advised to get the Delphi O2s.
No fuel smell under hood but I do get exhaust smell similar to exhaust pipe leading me to believe flex pipe since it is the original and untouched. Does not seem broken from top but I will have a better idea when I lift it up and check.
So my scanner is showing some really high ST/LT's. ST = 32 and LT=29. O2s fluctuate very slow and when I rev the fuel trim drops to about 2 and sometimes in the negative but when I release, it goes back up prompting a leak somewhere from my experience. Only leak that might be issue and I have not fully inspected due to not being able to put on lift is the flex pipe.
11-03-2022, 09:54 PM
#25
Member
Thread Starter
Join Date: 12-17-2010
Location: High Desert, CA...
Posts: 51
***UPDATE***
Disconnected purge valve line going to the back of the vehicle and smoked it. I was near the driver rear well waiting for smoke and did not get anything but then I was walking around and noticed smoke coming from the passenger rear wheel well as well as when I removed the cap from the fuel filler it was also smoking inside and coming out.
Does that mean the canister sensor is open?
Disconnected purge valve line going to the back of the vehicle and smoked it. I was near the driver rear well waiting for smoke and did not get anything but then I was walking around and noticed smoke coming from the passenger rear wheel well as well as when I removed the cap from the fuel filler it was also smoking inside and coming out.
Does that mean the canister sensor is open?
11-04-2022, 12:24 AM
#27
Member
Thread Starter
Join Date: 12-17-2010
Location: High Desert, CA...
Posts: 51
11-04-2022, 11:41 AM
#28
Moderator
Join Date: 01-23-2009
Location: Fredericksburg,VA
Posts: 25,325
Engine running the vent should close on and off. It closes when the purge opens and so forth. I'm not sure if key on not running does it.
Did you try blowing through the purge valve?
The #1 O2 sensor should fluctuate rapidly and wildly, the #2 be pretty steady (both depending on the scale setting). LTFT should stay around + or - 10%
Here is the entire article from the Service Manual:
p0171.pdf
Did you try blowing through the purge valve?
The #1 O2 sensor should fluctuate rapidly and wildly, the #2 be pretty steady (both depending on the scale setting). LTFT should stay around + or - 10%
Here is the entire article from the Service Manual:
p0171.pdf
11-05-2022, 02:55 AM
#29
Member
Thread Starter
Join Date: 12-17-2010
Location: High Desert, CA...
Posts: 51
After changing upstream O2, the ST/LT fuel trims improved to a more normal level %.
What I did end up finding was a deteriorated vacuum plug right under the throttle body on the manifold, popped it off and put a new one on.
Let it idle for a good 15 min, then took it for a spin on the freeway about 20 mins and came back home. Hooked up scanner and no P0171. Usually just idling it would come back after sitting for a couple of mins.
One thing I did notice is a burning smell coming from under the hood after my drive, nothing was melting but I did feel heat coming near the top of the flex pipe, felt like a heater and not like normal radiating heat from exhaust system . Hope it is not a cracked manifold.
Will get on it and provide updates.
What I did end up finding was a deteriorated vacuum plug right under the throttle body on the manifold, popped it off and put a new one on.
Let it idle for a good 15 min, then took it for a spin on the freeway about 20 mins and came back home. Hooked up scanner and no P0171. Usually just idling it would come back after sitting for a couple of mins.
One thing I did notice is a burning smell coming from under the hood after my drive, nothing was melting but I did feel heat coming near the top of the flex pipe, felt like a heater and not like normal radiating heat from exhaust system . Hope it is not a cracked manifold.
Will get on it and provide updates.
