Hello all I'm new to these forums but I have read them for a while and it's time I made an account myself. Yesterday I was driving my rig on the highway and about 80mph when my check engine light came on. I brought it to my trade school where I work on cArs to become a mechanic in a ase certified course. The code that came up was P0141- Engine running too lean, my teacher smoked the engine but we did not find a leak, we accessed my Mass airflow sensor and cleaned it with carb cleaner which my teacher suggested to use. We reset the code but my rig is running like shit, it seems to have trouble starting itself but it still does without a problem. The car seems slower and my engine used to have a whine to it, the whine is completely gone and the car seems to be limiting itself. I brought it to my mechanic today for a full tune up and replace the maf specifically. Any advice from you guys on what I should do?
3rd gen 2000 4Runner P0141 running too lean Help!
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allwheeldrive
New member
If it's a 171, probably the maf. Cleaning it rarely works, and you could have made it worse by trying to clean it.
I had a similar issue, I threw p0141 among others. My FIRST suggestion is very easy. There is a ground wire on the intake plenum in front of the diagnostic port. Tighten that down if it's at all loose. Reset ECU and check it out. I went through a ton of work and $$$ replacing sensors and what not and this was my issue.
After that, check the rear 02 sensor. A replacement is about 60 bucks and easy to install if it's not rusted in there. mine was so bad I had to replace the rear cat along with it just to get the sensor out. Be sure to use Denso 02 sensors only. Here is the site with the part numbers for various 2000's.
Look up part number and order from amazon.
Oxygen / AFR Sensors - Underdog Racing Development
After that, check the rear 02 sensor. A replacement is about 60 bucks and easy to install if it's not rusted in there. mine was so bad I had to replace the rear cat along with it just to get the sensor out. Be sure to use Denso 02 sensors only. Here is the site with the part numbers for various 2000's.
Look up part number and order from amazon.
Oxygen / AFR Sensors - Underdog Racing Development
TheDurk
Elite Member
I completely disgree. MAF needs to be cleaned regularly as I have done every 30k since 1999. Still on original MAF and no P0171 here. If you ruin a MAF by cleaning it, you're doing it wrong.
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TheDurk
Elite Member
allwheeldrive
New member
I respect your input, but if the maf is at its point where you are getting a 171, cleaning hardly solves the problem. You may be able to get by for a while, but at some point a new sensor is the way to go. If it's dirty enough, it's real difficult to clean the platinum hot wire with only some cleaner. That's been my experience with Toyota mafs.
JayRolla
New member
Respect your input but you said cleaning maf makes it worse. In my eexperience with any maf or sensor it don't work to well when dirty. Just my opinion.
TheDurk
Elite Member
Sometimes, sure. But you would be irresponsible, or a typical dealer tech, to swap an expensive part without trying to clean it first. Plenty of people on here have cured their P0171's with a simple cleaning. I certainly see a major difference every time I clean mine. It goes from black to bright platinum.
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Quick update, the p0171 code came back, I noticed it came on at highway speeds as I drove on the freeway given both times I was driving around 60-70 mph which has never happened to me before. I cleared the code this noon but it began to drive bad as I came back from class, my mechanic then drove it and somehow everything is back to normal. Light came back on 10 minutes ago on my drive home. Tommorow I'm going to buy that maf sensor cleaner and run seafoam through the engine. Thanks for the advice.
NEVER Carb cleaner--that's Doing It Wrong 101.
I'm buying this stuff tommorow. Thanks for your input, how much of the can should I use. Also found out that I'm running lean in bank/bay 1 I may switch my mass air flow sensor what do you think? My car is still not running as well as it was before this happened.
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TheDurk
Elite Member
Just keep firing 3 second bursts at it until the wire is bright. One can does several good cleanings. Make sure you are shooting at the right wire.
This should help:
Toyota 4Runner Highlander Mass Air Flow Sensor MAF cleaning
I wouldn't swap the MAF until I had tried everything else because it is big $$. Did you go through the FSM?
http://tacoma.site40.net/4Runner_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/02toyrm/02toypdf/02rmsour/2002/024runne/di/eg5vzfe/cip0171p.pdf
http://tacoma.site40.net/4Runner_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/02toyrm/02toypdf/02rmsour/2002/024runne/sf5vzfe/mafm/insp.pdf
There are two different types of MAF, depending on year. If you buy new, and you have the older type, consider upgrading to the '99+. It is both cheaper and better.
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