Help!!! P0171!!!

Went to clean the MAF...picture below was what it looked like pulling it out...needless to say, it likely can't be cleaned any more, so it is either bad, or the 02 sensors are. I ordered both front and back and they will be here Wednesday. I am so glad mine isn't a Cali spec. Also turns out the CEL is burned out and that is why this whole thing came as a surprise. Hopefully I didn't do too much damage to the cat. I am sort of thinking about swapping MAF/air boxes between my two 4runners and seeing if the one throws a code in the other, good or bad idea? I have a blue tooth scanner on the way, so soon I will be more in touch.

 
Replaced the pre cat O2 sensor with Denso 234-4162. 234-4153 (as described on Amazon by reviewers who drove 3rd gens), was supposed to have a longer lead for the rear O2 sensor...however, my 99 and 00 runners have equal length leads and look to use the exact same O2 sensor for both positions.

Once I replaced it, drove over to the Zone and had them read my code...only came up with loose gas cap. Drove it last night and today and will go and get a retest done to see if that cleared. Bluetooth OBDII will be here tomorrow, can't wait, and really hoping I solved my issue.
 
P0171 came back, so I popped in a new MAF and have driven 30 miles with no light. Pretty sure that did the trick. 163k on the original MAF.
 
Nates_NW4Runner said:
Fightman,

I was just looking through your build thread and noticed you just recently got a K&N filter from someone... If you have already installed it, this may be your culprit.:shrug: just thinking out loud...
If I were you, I would clean it this time and see how long it takes for the light to come back on then check the MAF to see if it is gummed up again. If it is, I would go back to a paper filter. Again, just thinking out loud.

Good luck and happy motoring :driving:
Click to expand...
i am also experiencing this issue. I got the truck with a K&n filter installed..The guys at the repair shop told me that my MAF was bad. i put in a new one, and also an O2 sensor( i am in the islands, so these are pretty expensive down here) . yet still the check engine light is still there with same code. i am thinking now of purchasing the air resonator( which was removed by previous owner ) and go back to original clothe filter. do u guys think this will help?
 
171 with a 306...

Hey guys new member here.. just picked up a 97 and it's throwing a 171 and a 306 engine code. The guy said it needed the coil, so I threw that at it with no change. Pulled the MAF sensor and cleaned that up as best I could, looked at the plug, it's running a paper air filter (not a k&n)... She has 264k on it but looks like the exhaust is pretty new... Anyone have ideas? Could the two codes be related? I've only run one tank of gas through it and got 15 with mostly highway miles..

Help. Haha, thanks
 
Newbie here

Looking for some advice in the P0171 area. Have a 98 3.4L Auto, throwing 2x P0171 codes (one pending) causing my car to not start occasionally after getting warm or longer drive times. Tried cleaning my OEM Denso MAF, code came back. Cleaned again and swapped out the front O2 sensor with a Denso Universal (had to attach to original plug?), code came back and upon cold drive had serious lag, still not wanting to start after long drives or getting warm. Finally broke down and purchased a NEW Spectra MAF off Amazon (Had great reviews unlike most the others I've heard of), after install (and reattaching battery wire) car would fire up then slowly putter and die. No check engine code, nada. Just would keep firing, putter, and die. Finally decided to take out and of course the front end got stuck in the air intake hose and broke off exposing wires. Ordered replacement and same deal. Put the old one back on but dont know where to go from here. New air filter and looking into replacing fuel filter. Anyone have experience with the spectra MAF? Dont know too much about cars but this is my daily driver and serious work vehicle so I need it running.
 
P0171 is excessive leaness, how has the fuel mileage been lately?

I would focus on ensuring a complete, 100% airtight passage way from the air cleaner to the metal intake. Double and triple check every rubber to plastic to metal connection. I found cracks in the last rubber intake 'hose' before the metal intake. Replaced that with OEM and it now idles unbelievably smooth, never thought it could be that smooth. Luck. :cowboy:
 
jgue467 said:
P0171 is excessive leaness, how has the fuel mileage been lately?

I would focus on ensuring a complete, 100% airtight passage way from the air cleaner to the metal intake. Double and triple check every rubber to plastic to metal connection. I found cracks in the last rubber intake 'hose' before the metal intake. Replaced that with OEM and it now idles unbelievably smooth, never thought it could be that smooth. Luck. :cowboy:
Click to expand...

:iagree:

Also, check all of your vacuum hoses for routing and any other issues, along with the PCV and grommet. Doing all of that, and cleaning the MAF, cleared my P0171 issue, and fixed the lean/low gas mileage problem.
 
I’ll document my P0171 journey here also. I had a 29.6 LTFT and I couldn’t find any vacuum leaks. I put a rebuilt engine in and this code popped up instantly on first drive.

I’ve triple checked vacuum lines. If I go wide open throttle my O2 bank 1 sensor 1 volts are .990 so the fuel delivery looks good in open loop at wide open throttle.

I’ve cleaned the 97’s MAF and it didn’t solve the issue. However I need to use my glasses and make sure I’m cleaning the proper spot.

I found cracks in the intake tube and replaced it with a good crack free spare from a 96.

The fuel rail and injectors sat for 3 years. I cleaned and rebuilt the injectors so I think they’re ok. The fuel filter looks old as dirt and I will replace it. The pressure regulator on the fuel rail sat open for those 3 years. I hit it a few times and my LTFT went down to 14.8. For the record, the 171 code only happens while driving. At idle it ignores the number.

Saga continues.......


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7f1dfb1a4958d8d13de153998bd31578.jpg

The above and below is the 97 puppy hauler to compare parameters.
1a89a0b9c14645c96bbecb9540acfe29.jpg


I have three MAF’s I did the above to compare to my engine.


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I Swapped out the MAF at work for my drive home and have the same MAF reading at idle as the other.

It sure does seem like I have a vacuum leak and it’s showing up as low airflow through the MAF sensor.

I bought a preCat O2 sensor and I’ll work on replacing it even thought the MAF reading is lower than my Ex’s 97 puppy hauler.



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So, my problem ended up being the throttle body gasket. I put it on in the wrong position.

A MAF reading around .520 lbs/min is a good number. Anything less is a vacuum leak. I was at .390 before I found the problem.


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now im starting to have this issue with the po171 code during this time i also got the p1130 code once as well but it has not come back. rig is running rich my afrs are 9.6-10afrs at cruzing speed on the fwy and idle.

the original maf has been cleaned and also replaced with a new denso unit. no vacumn leaks,no fuel leaks, it has a little rough idle and running extremely rich.reset computer mutiple times by discontecting battery and pulling efi fuse. but it still runs rich and idles a little rought still and code comes back on when i wot itto see if my afr will change.

also the afr jumps from 9.6/10afr to 11-13ish afrs with hard throttle accelerations. but when i let off it jumps back to 9.6-10afrs coasting.

is it safe to say i should move on to replacing the a/f ratio sensor? or are there other things to check??
 
Here’s my 2¢.

Battled a 171 code for a hot minute.

Checked and rechecked everything. New TPS; known good MAF; new O2 sensor; ohmed the injectors (tested fine) replaced 4 of the 6 injectors with known good injectors.

Nothing fixed it.

For sh*ts and giggles I bought an ultrasonic cleaner and an injector tester.

Cleaned the injectors; code went away.

Turns out a partially clogged injector was causing my issue.

YMMV.


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