JSharp

I finally got around to cleaning the MAF sensor after having my check engine lamp come on a few weeks ago when pulling up a long hill at 75mph in 5th with the cruise on.

The check engine lamp would reset itself by the next moring but come on again after pulling another long hill. The scanner at Autozone gave a P0171 - bank 1 too lean code.

Removing the MAF, the temp sensor was clean but the airflow sensor wires were black. A little contact cleaner and some q-tips and I now have shiny sensor wires again.

Lets hope this fixes the lean code I was getting...

JSharp

Possibly. The intake plumbing was very clean though other than the sensor wires. I pulled the K&N a while back and replaced it with paper because I didn't like the silicon numbers I was getting when I did an oil anaylsis. Just forgot to change my sig.

Checking and cleaning the MAF is sure a no-brainer. Probably a good thing to do every 30K service...

midiwall

Since you've got the intake tube open to get to the MAF, it'd be a good idea to clean out the throttle body as well. You'll be amazed at how much goop you'll get out of there. Info is here on "dukestr"'s website:

http://www.thedukenetwork.net/4runner
Pick "Maintenance" then "Throttle Body" from the top line menu

dragr1

iTrader: (3)

With the code on, would you lose power big time at full throttle?



I'm having the same code and I've cleaned the MAF, throttle body, and checked for vacuum leaks. I just told the stealer to get me an O2 sensor (in front of cat). I hope that fixes it.

MTL_4runner

A bad O2 sensor usually gives a different code.
You may need a new MAF if cleaning does not help.

dragr1

iTrader: (3)

Anyone else? Throttle position sensor maybe?

dragr1

iTrader: (3)

Anyone else have suggestions for this? I have a thread going on another site also:

http://www.4x4wire.com/forums/showfl...5&o=14&fpart=1

MTL_4runner

If you have a junkyard near you I would see if they let you borrow another MAF (must be 99-02) to try out in the parking lot (only takes 2 secs to put one in). I remember someone in your exact same situation on Yotatech that even cleaned theirs with electrical contact cleaner to no avail. I really don't think it is the TPS and only has a small possibility in my book of being an O2 sensor but you never know.

The lean condition is almost always associated with the MAF:
https://www.yotatech.com/forums/show...ht=replace+maf


......unless you have a supercharger!


EDIT: Also did a bit of searching and forgot on 99+ tucks the front O2 sensor (bank 1, sensor 1) is actually an A/F ratio sensor not just a traditional O2 sensor like on the 96-98's. Here is someone who did have the same problem and the A/F sensor did the trick.....check it out.
https://www.yotatech.com/forums/show...ighlight=po171

Try using the search button, there is tons of stuff in there on this subject.

dragr1

iTrader: (3)

Thanks for all the help, I did do a search, but I didn't get all the threads you linked. I have cleaned the MAF with the dealer recommended throttle body cleaner. This was a couple of months ago and made no difference. I'm gonna try the maf swapout and then the O2 sensor.

MTL_4runner

Might want to pull the MAF out again and clean with some warm water and dishsoap.
If there is any residue on the MAF sensor it may not function correctly.
Just another thought.

dragr1

iTrader: (3)

I borrowed another MAF briefly and it definitely seemed to help. So today I traded my stock front bumper for a MAF and to sweeten the deal, I also got both O2 sensors and a TPS, woohoo. One of these should cure the problem. I'll do them one at a time, starting with the MAF and let you know what comes about. For good measure, do you think I should clean the MAF before installing, it's got a little dust on it. If so-water, throttle body cleaner, or Radio Shack electrical parts cleaner?

midiwall

Throttle body cleaner!


Good luck!

MTL_4runner

My preference would be electrical parts cleaner but I am sure soap and water would be fine too.

dragr1

iTrader: (3)

That is my thinking also.

kimchee

ive tried both throttle body/carb cleaner and electric contact cleaner. throttle body cleaner seems to leave a very light oily residue. contact cleaner leaves a very very faint dry residue. I doubt either residue is going to throw off the readings but i like to try and remove the residue afterwards with a cloth or something.

i havent used water and soap becuase im afraid of it not drying all the way very quickly. but thats just because im impatient.

JSharp

I used electrical contact cleaner that is safe for plastics, and a q-tip. The black film on the sensor wires wouldn't come off by just spraying with cleaner...

dragr1

iTrader: (3)

I found a MAF at a junkyard and finally replaced my MAF today. I drove around for about 30 miles and so far it seems much better. I hope it stays that way. Thanks for all the help!

MTL_4runner

Cool, glad to hear it!

dragr1

iTrader: (3)

I also noticed that the screws on my maf were almost stripped, so maybe this has been done before. I bought it used with about 55k miles, it has 78k miles now.