desertmtnbkr

I have a 2004 Sequoia on which I installed a K&N intake ~4 years ago. Never had any problem from the day it was installed. In late summer this year, the engine was hesitating on acceleration a little when cold. I dropped it with the mechanic who usually works on it to check it out. After a $200 bill, he said he couldn't find any issue, changed the PCV valve and cleaned the MAF sensor as said that "oiled" air filters tend to get the sensor dirty. I've read various arguments against that but that’s a topic for a different discussion.... Anyhow,.. no change/improvement to function. About a month later, I decided to perform some needed maintenance myself, prior to a long road trip hauling my boat, I performed a slightly more in-depth service: changed plugs, changed O2 sensors, changed fuel filter, drained-changed fluids, etc. Not long after, I had a trio of lights come on - Check Engine and the two VSC lights. However, I don't have the cold hesitation anymore. Running the codes on my reader indicated P0171 and P0174 indicating both banks are running too lean. I've searched all over this intake looking for a vacuum leak but no luck in finding one. Just to make sure, I went all over the air-intake double checking the tightness of clamps and I also pulled the MAF and cleaned it using MAF-specific cleaner. I reset the codes and sure enough, they came back on. It doesn’t seem to make sense that the problem is actually in the air-intake system as nothing was touched there during the service. The O2 sensors I installed were not OEM but BOSCH. I bought them at AutoZone and they matched the engine by their lists but the sensor ends look a little different. I wonder if the new sensors are simply the issue and I’m toying with the idea of purchasing and installing the OEM Denso versions but at $100/ea, that’s an expensive experiment. I've also wondered if the MAF sensor could have been damaged in the cleaning but I'm not getting an error code regarding it. Does anyone have any further suggestions before I bite the bullet and take it to the toyota dealer at $80/hr? Thanks.

waskillywabbit

iTrader: (-1)

My bet is non OEM O2 sensors.

:wabbit2:

desertmtnbkr

Thanks. I'm leaning that way too. Just an extra note, when I've reset the codes, I've tested it intermittantly while driving casually and the codes did not show. Only when I pushed it hard like passing up a hill did they pop up again. also, the after market BOSCH sensors have much fewer perforations for the gases compared to the OEM sensors so I'm wondering if they simply don't have the access to the passing gases for analysis thus incorrect reading.

Thelast83inNJ

Hello, isn't bank 1 sensor 1 an air/fuel ratio sensor not an ordinary oxygen sensor?

runneroffroad

Iv heard about 80% of the time when code 171 and 174 are on its the mass air flow sencor. So I would guess its bad.