MAF Sensor
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CL Community Team
Joined: Apr 2004
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From: Miami, Florida
MAF Sensor
I just got back from bracket racing up at the track...semifinalist out of 16 cars in the open division (not the points championship that I am usually in that took a siesta this month)...defeating a Corvette and a Camaro before losing in a very close race to 1967 Firebird (happy to lose to a mechanical rather than electronic wonder and he won 1st place in the final). My loss came way of breaking out of my set time by .030 seconds, which is big 
Why this story? I cleaned my MAF sensor earlier in the day and by doing so it may have pushed my car a little too fast over the course of my races, only killing my happy race day in the end. Fast times but you lose the race for inconsistency.
The MAF sensor of course is that sensor one finds after the airbox and has been subject to numerous discussions on this forum involving the K&N air filter and oil. I had this issue a few years ago, so I thought I would show the necessary areas that need cleaning.
Why this story? I cleaned my MAF sensor earlier in the day and by doing so it may have pushed my car a little too fast over the course of my races, only killing my happy race day in the end. Fast times but you lose the race for inconsistency.
The MAF sensor of course is that sensor one finds after the airbox and has been subject to numerous discussions on this forum involving the K&N air filter and oil. I had this issue a few years ago, so I thought I would show the necessary areas that need cleaning.
Last edited by Lexmex; Feb 26, 2006 at 09:46 PM.
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From: Miami, Florida
This red diode found on the MAF sensor is one of the possible culprits involved in the infamous P0171 OBDII code or the lean air error as I like to call it. There are numerous cleaning agents. I have used brake dust cleaner, while others may use carburator cleaner. This is the diode that in my case got coated with the K&N oil (nothing against K&N here as they do make fine products and I use their oil filter).
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CL Community Team
Joined: Apr 2004
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From: Miami, Florida
However, one of the most overlooked areas of the MAF sensor is the filament inside the sensor seen by turning the sensor upside down and looking inside.
Rather than using brake dust cleaner or carburator cleaner, it is better to use an electrical contacts cleaner. My uncle had a generic Mexican version of the stuff, but your local Radio Shack should have this (the ones in Mexico did not
) A short spray inside and blow a little air in ever so gently and repeat one more time and that should get it clean.
Maybe we are not racers at the track, but this can improve daily performance along with MPG. FYI, on the track this can help your times .2 to .3 in the 1/4 mile from a dirty MAF sensor (based on friends who have done the same with their own vehicles and never knew about this sensor). May not seem like much, but this is an eternity in racing.
Rather than using brake dust cleaner or carburator cleaner, it is better to use an electrical contacts cleaner. My uncle had a generic Mexican version of the stuff, but your local Radio Shack should have this (the ones in Mexico did not
) A short spray inside and blow a little air in ever so gently and repeat one more time and that should get it clean.Maybe we are not racers at the track, but this can improve daily performance along with MPG. FYI, on the track this can help your times .2 to .3 in the 1/4 mile from a dirty MAF sensor (based on friends who have done the same with their own vehicles and never knew about this sensor). May not seem like much, but this is an eternity in racing.
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Joined: Aug 2005
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From: Ukr
Originally Posted by Lexmex
This red diode found on the MAF sensor is one of the possible culprits involved in the infamous P0171 OBDII code or the lean air error as I like to call it...
Thanks for Info.
This "red diode" is Air Intake Temperature Sensor.
Sensitivity Element* ( possible reason to P0171) is situated into Tube of Sensor
Take a look
https://www.clublexus.com/forums/sho...d.php?t=182163
BR,
_______________________________
* http://www.alflash.narod.ru/NZ/36-1.gif and http://www.alflash.narod.ru/NZ/_3006.jpg
Thread Starter
CL Community Team
Joined: Apr 2004
Posts: 17,321
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From: Miami, Florida
[QUOTE=alflash]Hello,
Thanks for Info.
This "red diode" is Air Intake Temperature Sensor.
Sensitivity Element* ( possible reason to P0171) is situated into Tube of Sensor
Take a look
https://www.clublexus.com/forums/sho...d.php?t=182163
BR,
Any time (with the K&N filter) that I got the P0171 error, I only cleaned the red diode...pulled the EFI fuse and that was the end of it until I decided just to reoil the front side of the filter. Never even touched the Sensitivity Element.
My current P0171 errors are rare and stem not from racing but actual traffic conditions where the car will coast (especially downhill) under light acceleration and then throw an error (lean error). I really do not worry about this one at all. When I give it WOT, absolutely no error since then the RX is getting is fuel into the mix more efficiently.
Thanks for Info.
This "red diode" is Air Intake Temperature Sensor.
Sensitivity Element* ( possible reason to P0171) is situated into Tube of Sensor
Take a look
https://www.clublexus.com/forums/sho...d.php?t=182163
BR,
Any time (with the K&N filter) that I got the P0171 error, I only cleaned the red diode...pulled the EFI fuse and that was the end of it until I decided just to reoil the front side of the filter. Never even touched the Sensitivity Element.
My current P0171 errors are rare and stem not from racing but actual traffic conditions where the car will coast (especially downhill) under light acceleration and then throw an error (lean error). I really do not worry about this one at all. When I give it WOT, absolutely no error since then the RX is getting is fuel into the mix more efficiently.
Lexus Champion
Joined: Jan 2005
Posts: 2,447
Likes: 9
From: CA
I believe thin wire sensor detects air flow rate, diode sensor detects inlet air temperature. Yes, good practice to clean them both. Here is a good DIY link with pictures.
http://www.lexusownersclub.co.uk/kno...v2&id=152&c=11
http://www.lexusownersclub.co.uk/kno...v2&id=152&c=11
Last edited by TunedRX300; Feb 27, 2006 at 01:52 PM.
Thread Starter
CL Community Team
Joined: Apr 2004
Posts: 17,321
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From: Miami, Florida
Originally Posted by TunedRX300
I believe thin wire sensor detects air flow rate, diode sensor detects inlet air temperature. Yes, good practice to clean them both. Here is a good DIY link with pictures.
http://www.lexusownersclub.co.uk/kno...v2&id=152&c=11
http://www.lexusownersclub.co.uk/kno...v2&id=152&c=11
I should add that given that my air mod, I get more particles flying in their at the track, so those filaments do get dirtier than most.
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Joined: Dec 2002
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From: OH
Funny you mention the MAF. We just took a 2,000 mile road trip and guess what error popped up the night before we left? 
Anyway, we had it reset and figured it was bad gas, but at about 500 miles into the trip it came on again. It turns out the MAF was bad and we had it replaced at a Toyota dealership, which cost nearly $300 inluding labor.
We also have had a K&N panel filter in the vehicle for about 4,500 miles. Do you think the K&N caused it? It was right out of the box and I figured they would not have too much oil on them after you buy them? The RX has about 105,000 miles on it right now so it is about time for things like this to start failing.
Anyway on the positive side, the CEL is gone and the RX drives great. For the hell of it, I put in the stock filter and our average MPG actually dropped by about 1.5.
The K&N is back in and thanks to this post I will just clean it the next time the CEL comes on. We should be back up to our 19.5 MPG again
Thanks.
Anyway, we had it reset and figured it was bad gas, but at about 500 miles into the trip it came on again. It turns out the MAF was bad and we had it replaced at a Toyota dealership, which cost nearly $300 inluding labor.
We also have had a K&N panel filter in the vehicle for about 4,500 miles. Do you think the K&N caused it? It was right out of the box and I figured they would not have too much oil on them after you buy them? The RX has about 105,000 miles on it right now so it is about time for things like this to start failing.
Anyway on the positive side, the CEL is gone and the RX drives great. For the hell of it, I put in the stock filter and our average MPG actually dropped by about 1.5.
The K&N is back in and thanks to this post I will just clean it the next time the CEL comes on. We should be back up to our 19.5 MPG again
Thanks.
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Thread Starter
CL Community Team
Joined: Apr 2004
Posts: 17,321
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From: Miami, Florida
Probably not that soon. I have gotten MAF errors in previous years when descending in altitude from Mexico City. It could have been too much air (even for less than a second) and that could have screwed things up...another form of the P0171 lean error. I always keep an OBDII scanner (you can get them for under $100 USD easily) to see what is up.
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