Hello all...new to this forum....had a question..........I have a 99 4 runner with about 96k miles. Everytime i floor it to merge on the freeway or just step on somewhat hard.....i tend to get a check engine light...the truck feels fine and all......I have not diagnosed the code yet.....but plan on taking in to autozone to read the code this weekend?...anu ideas on what it can be....it only happens when i give it more than half throttle and the RPMS climb....not to red line but between 4-5500....any suggestions are greatly appreciated. Thanks!

 

how troublesome....no suggestions...............

 

Absolutely not even worth guessing until you get that OBD code.

 

That's very unusual, to have it only come on then (and goes immediately off, I presume?...). The CEL typically comes on and stays on until you reset the ECU from what I understand.

5500 rpm? OUCH!!!

 

well the checl engine light stays on...but i reset the ecu everytime because its annoying......i guess my truck doesnt like when i step on it...

 

Now THAT is beginning to sound like the MAF needing a good cleaning...

 

Or a lean condition from a pluggged injector, or fuel filter, or a bogus O2 reading, or a "slow" O2 reading, or any of 30 other different things.


994runnerguy... Stop resetting the ECU - you're only masking a problem, the CEL is there to tell you that something's up. "Resetting the ECU" doesn't clear the code - it's still there stored in memory. It'll come back unless it sees the condition clear.

Get the code read and please post it up here...

 

Ok....i went to autozone to get the code checked out....it turns out that its code P071 i think...it read.....system too lean...bank 2.......so i was thinking it was the pre-cat o2 sensor. they offered me a bosch o2 sensor for like $380.....so what do you guy sthink it cou;d be? any help is greatly appreciated!

 

Now that you have the code, you're still just pissing in the wind until you get a FSM (factory service manual) and follow the diagnosis procedure for that code to determine what the TRUE problem is. You follow what the book tells you to do and eventually you will eliminate the sources one by one until you find the culprit.

FYI: OEM O2 sensors are $80 from any online Toyota dealer. Don't do bosch - do OEm DENSO (toyota) O2 - if that is the problem.

 

i think i might do that......so far i have cleaned out the MAF, air filter, plugs, i took off the 02 sensors and cleanes them w/electronic safe chemical.....the only thing i havent done is the fuel filter.....i have a 99 4runner and was wondering where the fuel filter is located...any help ios greatly appreciated...thanks!!!

 

underneath the driver side door along the frame rail to the inside.

 

I had this same problem. My check engine light would come on when accelerating to get on the highway, then after a week or so, it would turn off. It probably did it about 4 or 5 times and everytime it was when I was accelerating to get on the highway. I finally cleaned the MAF and so far, after about three weeks, I haven't seen the check engine light. It also took care of a hesitation problem I was having!!
So that might be something to try before spending money on a sensor.

 

i got a similar code when it was my MAF.

 

ik going to replace the fuel filter today....ill also give the maf another good cleaning!!! thanks for the help guys!!!!!!

 

fuel filter is about $38 from toyota. you can get one from autozone/napa etc for about $20 if a dealer isn't close by.

 

From the tech write-up section here on the forum:
https://www.yotatech.com/~corey/tech/techpage.htm

Comes a link to the Maintenance page:
https://www.yotatech.com/~corey/tech/techpage3.htm

Which leads to a link to this article, which may help:
http://www.4runners.org/articles/fuelfilter/


Have fun! (and heed the warning about eye protection and having a bucket handy!)

 

You might also want to look at this little thread too....
https://www.yotatech.com/forums/show...ighlight=p0171

If you do a search for the code you get tons of great reading!
https://www.yotatech.com/search.php?searchid=289895