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Chasitek

TJ Enthusiast
Feb 19, 2018
304
Chapel Hill, NC, USA
So this is NOT TJ related and I know it shouldn’t be posted in this section but I’m in dire need of smart people knowledge. Aka tj forum knowledge. My girlfriend has an 07 FJ cruiser that was throwing code P0101 “mass or volume air flow sensor “A” circuit range/performance” I replaced the MAF with a spectre one and the code went away for a week and then came back. Since it was under a 3rd party warranty i brought it in to the dealership and they said it needed a OEM sensor. Well before Spending the money, I exchanged the spectre one for another spectre one which caused the engine to misfire. It also would start and then instantly die. Finally it stayed alive and the rpms were bouncing up and down. The current codes that are being thrown are the P0101, P0171, and P0174. I just got an OEM sensor and the first couple start ups the car would just die after being started. Finally it stayed running and I test drove it around the neighborhood. All was going great and then going down a hill all the lights came on on the dash and then I lost power steering but the car did not die. I cut the car off and started it but it instantly died. In order to keep it running I have to give it gas or it will immediately die. If i rev it, the car kind of sputters. It’s not a consistent rev sound if that makes sense. I was thinking when I lost power steering that it could be the alternator but everything starts up fine and is going fine. Over the break we were at my moms house but school starts tomorrow so I really need it fixed to get back. The FJ forum does not respond at all. All help is GREATLY appreciated.


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Chris

Administrator
Staff Member
Sep 28, 2015
38,061
Salem, Oregon
Do you have an ODBII scanner? If so, scan it and see what codes it's currently throwing, as well as any potentially "pending" codes. It's possible there are more codes now with the current issues you're having.
 
OP
Chasitek

Chasitek

TJ Enthusiast
Feb 19, 2018
304
Chapel Hill, NC, USA
Do you have an ODBII scanner? If so, scan it and see what codes it's currently throwing, as well as any potentially "pending" codes. It's possible there are more codes now with the current issues you're having.
Current codes are P0101, P0171, and P0174. I’m assuming this makes it either fuel related or sensor related.


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Chris

Administrator
Staff Member
Sep 28, 2015
38,061
Salem, Oregon
P0101 Causes
  • Dirty, obstructed, or faulty mass air flow sensor
  • Damaged or disconnected air intake boot (snorkel)
  • Vacuum leak
  • Clogged or improperly installed air filter
  • Clogged catalytic converter / restricted exhaust

P0171 Causes
  • Dirty or faulty mass air flow sensor
  • Vacuum leaks – PCV hose, vacuum hoses, intake manifold gasket.
  • Weak fuel pump
  • Clogged or dirty fuel injectors
  • Exhaust leak
  • Faulty oxygen sensor

P0174 Causes
  • Dirty or faulty mass air flow sensor
  • Vacuum leaks – PCV hose, vacuum hoses, intake manifold gasket.
  • Weak fuel pump
  • Clogged or dirty fuel injectors
  • Exhaust leak
In other words, everything seems to be pointing to your MAF sensor. You could have a bad O2 sensor or a weak fuel pump that is going bad. I'd also be inspecting very carefully for vacuum leaks as well.

If it were me, I might actually start by resetting the ECU. Unplug the battery for 10 minutes and let it sit. Plug it back in, then see what happens.
 
OP
Chasitek

Chasitek

TJ Enthusiast
Feb 19, 2018
304
Chapel Hill, NC, USA
P0101 Causes
  • Dirty, obstructed, or faulty mass air flow sensor
  • Damaged or disconnected air intake boot (snorkel)
  • Vacuum leak
  • Clogged or improperly installed air filter
  • Clogged catalytic converter / restricted exhaust

P0171 Causes
  • Dirty or faulty mass air flow sensor
  • Vacuum leaks – PCV hose, vacuum hoses, intake manifold gasket.
  • Weak fuel pump
  • Clogged or dirty fuel injectors
  • Exhaust leak
  • Faulty oxygen sensor

P0174 Causes
  • Dirty or faulty mass air flow sensor
  • Vacuum leaks – PCV hose, vacuum hoses, intake manifold gasket.
  • Weak fuel pump
  • Clogged or dirty fuel injectors
  • Exhaust leak
In other words, everything seems to be pointing to your MAF sensor. You could have a bad O2 sensor or a weak fuel pump that is going bad. I'd also be inspecting very carefully for vacuum leaks as well.

If it were me, I might actually start by resetting the ECU. Unplug the battery for 10 minutes and let it sit. Plug it back in, then see what happens.
I tried the battery disconnect after I replaced the first spectre sensor which got the car to stay running. However, i didn’t remove it for 10 minutes. Just a minute. Nothing was wrong until I replaced the first spectre MAF with the second one. Ever since things have gone down the drain and no sensor is making it run. Originally when I first got a check engine light way back when, i got a P0171, P0174, P0101, P0420. Then when I originally replaced the MAF for the first time, the P0420 went away and has since not come back. I will try disconnecting the battery again for longer as well as check for vacuum leaks but it’s hard to check for leaks when the car won’t idle. I usually spray carb cleaner or something to check. There were No signs of any conditions until the MAF was changed. However i do know the intake filter isn’t connected the best but it was running fine even with it not the best and it hasn’t been touched at all since the conditions have happened.


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Chris

Administrator
Staff Member
Sep 28, 2015
38,061
Salem, Oregon
Try resetting the battery by leaving it unplugged for 10 minutes. It's worth a shot.

1-minute wouldn't be long enough to reset the ECU.

What do you mean the intake filter "isn't connected the best"?
 
OP
Chasitek

Chasitek

TJ Enthusiast
Feb 19, 2018
304
Chapel Hill, NC, USA
Try resetting the battery by leaving it unplugged for 10 minutes. It's worth a shot.

1-minute wouldn't be long enough to reset the ECU.

What do you mean the intake filter "isn't connected the best"?
Well it’s an aftermarket TRD 1st gen air intake round air filter that’s housed inside a box. The box is supposed to be against the fender which pulls air from the outside but there’s a small gap in between the box and fender. Not a big gap but a gap nonetheless. Also the tube from the filter itself to the TB is missing a coupling so the seal isn’t air tight however I didn’t think it was a huge deal since it’s before the MAF. It’s not a big leak or anything it’s just not tightly snug against the tube. I’ll take a picture.


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OP
Chasitek

Chasitek

TJ Enthusiast
Feb 19, 2018
304
Chapel Hill, NC, USA
Try resetting the battery by leaving it unplugged for 10 minutes. It's worth a shot.

1-minute wouldn't be long enough to reset the ECU.

What do you mean the intake filter "isn't connected the best"?
ef23a26bcdf41d787bf381a4e8f74c92.jpg

Here is a picture of the intake system. It’s just a general photo since i’m not home but the part
circled in green is missing that red coupling but there’s a silicone tube in place that is a smaller diameter than the hard plastic tube but it’s perfectly smaller than the hard tube so it’s not an air tight fit. It slides into the hard tube with no effort.


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Chris

Administrator
Staff Member
Sep 28, 2015
38,061
Salem, Oregon
Do you happen to have the stock airbox? If so, it would be worth putting it on to see what happens. You know... rule it out at least.
 
OP
Chasitek

Chasitek

TJ Enthusiast
Feb 19, 2018
304
Chapel Hill, NC, USA
Do you happen to have the stock airbox? If so, it would be worth putting it on to see what happens. You know... rule it out at least.
Nope. It came with this one. I would love to go back to stock as the stock one was a good CAI. i will try and track down a coupling that works. It’s like a 4.25” diameter so i’ll look in plumbing at lowes or something. I told my girlfriend to unplug the negative terminal and see what happens so i’ll let you know what she says happens when she puts it back on.


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OP
Chasitek

Chasitek

TJ Enthusiast
Feb 19, 2018
304
Chapel Hill, NC, USA
Do you happen to have the stock airbox? If so, it would be worth putting it on to see what happens. You know... rule it out at least.
Well she said so far since the ecu reset, she started it up normally and it is idling normally. However, it seems to always be fine when it’s a cold start and after a few minutes of driving, it starts to struggle.


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mots

TJ Enthusiast
May 11, 2018
917
OH, USA
I don't know these motors, but I see a MAF sensor after where the air leak is presumably at. From your readings, it seems odd that the LTFT's are pulling that much fuel. Not much to see with STFT at idle. So, perhaps the turbulence of the leak is causing the MAF to read incorrectly and causing the ECU to assume there is more air than there really is coming in from the intake. This causes the ECU to to try to dump more fuel to correct, but the O2 sensors are reporting back to stop dumping the extra fuel. The ECU then adjusts and pulls the extra fuel (as shown in the LTFT's).

I would fix the leak, either properly or by using duct tape or gorilla tape as a make-shift gasket. Then, reset the ECU again, and see if it fixes it.
 
OP
Chasitek

Chasitek

TJ Enthusiast
Feb 19, 2018
304
Chapel Hill, NC, USA
I don't know these motors, but I see a MAF sensor after where the air leak is presumably at. From your readings, it seems odd that the LTFT's are pulling that much fuel. Not much to see with STFT at idle. So, perhaps the turbulence of the leak is causing the MAF to read incorrectly and causing the ECU to assume there is more air than there really is coming in from the intake. This causes the ECU to to try to dump more fuel to correct, but the O2 sensors are reporting back to stop dumping the extra fuel. The ECU then adjusts and pulls the extra fuel (as shown in the LTFT's).

I would fix the leak, either properly or by using duct tape or gorilla tape as a make-shift gasket. Then, reset the ECU again, and see if it fixes it.
Ok i’ll try that and report back. Thanks. Also it’s the same engine as the 2004-2015 tacomas. 4.0 L 1GR-FE V6

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Last edited:
OP
Chasitek

Chasitek

TJ Enthusiast
Feb 19, 2018
304
Chapel Hill, NC, USA
I don't know these motors, but I see a MAF sensor after where the air leak is presumably at. From your readings, it seems odd that the LTFT's are pulling that much fuel. Not much to see with STFT at idle. So, perhaps the turbulence of the leak is causing the MAF to read incorrectly and causing the ECU to assume there is more air than there really is coming in from the intake. This causes the ECU to to try to dump more fuel to correct, but the O2 sensors are reporting back to stop dumping the extra fuel. The ECU then adjusts and pulls the extra fuel (as shown in the LTFT's).

I would fix the leak, either properly or by using duct tape or gorilla tape as a make-shift gasket. Then, reset the ECU again, and see if it fixes it.
Well I taped the intake up and reset the ecu again and still having codes p0172 and p0175 and now p0101. It’s at least drivable but this is ridiculously stupid. Also i attached a picture of where the leak is at.
048918a0d292663c8a6f7c0b6debfd5f.jpg
c5e77b9c958d96343a7153963d1f77f4.jpg



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Last edited:

mots

TJ Enthusiast
May 11, 2018
917
OH, USA
The leak was pre-MAF, so it theoretically shouldn't have affected things, but it is good to get that sealed up. I'd also grab a cheap worm clamp and remove the tape, then at least you've done well for them there ;). Also make sure the air intake after the MAF going into the engine doesn't have any "post MAF" leaks.

Since p0101 is for the Mass Airflow sensor circuit, I'd definitely think about replacing the sensor with OEM sensor as recommended. If the connector is corroded, check that first and make sure the sensor is making good contact and also look for other potential wiring harness issues. That may save you from getting an OEM sensor if it is just not making a good connection into the wiring harness. Use electrical parts cleaner to clean it up the connector on the wiring harness if it has corrosion inside. If all looks good and you still are having issues, then I'd try a new OEM MAF sensor. We have found Jeeps not liking aftermarket sensors as well, so it wouldn't be a surprise if you needed an OEM sensor for it to work properly.

The "hot wire" inside the MAF sensor is very fragile, so be very careful not touch or damage while installing. There may be other issues as well, but this is the best place to start since the ECU is telling you the MAF is an issue. Cars that have a MAF sensor have a table inside the ECU that translates sensor voltage reported to grams of air coming in. The ECU uses this air mass value along with some other variables to know how much fuel to add under different engine conditions. If the voltage is reported improperly by a failed sensor, you can see how this would confuse the engine it put it into reactive mode all the time.

Good luck!
 
OP
Chasitek

Chasitek

TJ Enthusiast
Feb 19, 2018
304
Chapel Hill, NC, USA
The leak was pre-MAF, so it theoretically shouldn't have affected things, but it is good to get that sealed up. I'd also grab a cheap worm clamp and remove the tape, then at least you've done well for them there ;). Also make sure the air intake after the MAF going into the engine doesn't have any "post MAF" leaks.

Since p0101 is for the Mass Airflow sensor circuit, I'd definitely think about replacing the sensor with OEM sensor as recommended. If the connector is corroded, check that first and make sure the sensor is making good contact and also look for other potential wiring harness issues. That may save you from getting an OEM sensor if it is just not making a good connection into the wiring harness. Use electrical parts cleaner to clean it up the connector on the wiring harness if it has corrosion inside. If all looks good and you still are having issues, then I'd try a new OEM MAF sensor. We have found Jeeps not liking aftermarket sensors as well, so it wouldn't be a surprise if you needed an OEM sensor for it to work properly.

The "hot wire" inside the MAF sensor is very fragile, so be very careful not touch or damage while installing. There may be other issues as well, but this is the best place to start since the ECU is telling you the MAF is an issue. Cars that have a MAF sensor have a table inside the ECU that translates sensor voltage reported to grams of air coming in. The ECU uses this air mass value along with some other variables to know how much fuel to add under different engine conditions. If the voltage is reported improperly by a failed sensor, you can see how this would confuse the engine it put it into reactive mode all the time.

Good luck!
The MAF sensor that is on it right now is from the dealership. It says toyota but it also says denso. It cost me a whopping $240 for the damn thing so i was hoping it would fix it as that is what the dealership was the problem. I cleaned the electrical with electrical cleaner. So far it’s running fine as in it will get us back home but I would still like to clear these damn codes. I will order a coupling to properly fix the air intake seal. It’s just weird to me that it was showing everything as lean but is now showing everything as too rich. Makes me think it is indeed another bad sensor but again, it’s from the dealership. They also said once the package is opened and the sensor has been installed, it cannot be returned. Also, i can’t put a worm clamp on there are the tube is hard plastic, it won’t compress at all.

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OP
Chasitek

Chasitek

TJ Enthusiast
Feb 19, 2018
304
Chapel Hill, NC, USA
So we got the fj back to my house and driving on the highway, the fj would lurch/sputter kind of like a shudder when I went more than 50-55 and took my foot off the gas. So in english, when driving above 50-55mph and letting the car cruise, the car would sputter kinda like an extremeee engine brake if it were a manual. Wtf is wrong with this thing. I don’t have these kinds of problems with my tj. Why can’t it just be simple like a tj


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