Po 171 engine code - Toyota Nation Forum : Toyota Car and Truck Forums

cranedewd · 10-28-2011, 08:10 PM

I have an 03 matrix that i just put a cone style air filter and short intake on. I drove it for about 20 miles then the cel came on. I put it on my scanner and the Po 171 engine is lean code came up. Is there anything I can do to fix the lean problem? I also just replaced the catalytic converter to clear that code and to get it inspected. Would one have anything to do with the other? Any help would be appreciated! Thanks

***humanoid*** · 10-28-2011, 11:19 PM

Is the cone-type filter you put on an oiled type filter as well? If it is, the oil may have gotten onto the MAF sensor, throwing off that code. Maybe buy some MAF cleaner from an autoparts store and get that cleaned and see if that clears it. Worst comes to worst, take off the negative battery terminal for a few minutes and that should clear it for the time being.

cranedewd · 10-29-2011, 08:48 AM

thanks ill give it a shot.

**MattK&NFilters** · 12-08-2011, 03:52 PM

What brand of intake did you put on there? (I won't be upset if it's not a K&N, I promise)

cranedewd · 12-08-2011, 04:58 PM

No its not a k+n. Its a no name I bought on ebay.since my last post I've noticed the cel will go off after its been warm outside and I've driven 80 miles. As soon as it gets cold, below 65 degrees, the cel will come back on. Any ideas?

**MattK&NFilters** · 12-08-2011, 05:07 PM

It could be caused by a number of different things related to the intake, but I'd suspect your intake is sized such that is causes your MAF sensor to misreport the amount of air entering your engine, which then triggers your check engine light. Basically, poor quality intake system. Or there's the possibility that there's a leak somewhere in your intake tract that is allowing air to enter your motor unmetered (not going past the MAF sensor).

hardtopte72 · 12-08-2011, 07:15 PM

Like Matt said this is most likely caused by unmetered air entering your engine. If you havent already Clean out the MAF sensor. After that check the intake piping for leaks. IF there are no leaks this is almost guaranteed to be caused by a bad intake manifold gasket. There is a TSB for them on the 1ZZFE engine. I have replaced several and the fact that you stated it happens when it gets cold makes me 90% sure that is your problem. There is still a chance it could be caused by leaks elsewhere or even a bad VSV but I would bet it is your intake manifold gasket.