hi all!

my CEL came on tonite. haven't seen it in 3 yrs i've owned this truck. so i stood out in the rain for a while to pull the codes just to know what was triggering it.

i got a 25 AND a 26. haynes says "air/fuel faulty lean malf." and "air/fuel faulty rich malf." what??

i'm going to clear them tomorrow and drive to trigger the light again and pull the code then, see if one was old.

but since i'm thinking about it, but don't feel like doing anymore in the rain, i figured i'd post and see if anyone had this issue before, with both of these codes together, and what their source of trouble was.

hope everyone's having a decent sat. nite.
tj

 

get your injectors checked and check the injector wiring for the right volts.

 

so, 88... yup, those are the codes: lean and rich. Does it start up cold and idle above 900 or so- the colder it is, the higher it idles, then drop down to 725 once the engine warms up like it should? If so, there's some other things to check... but for clarification, this is EFI, not carb'd, right?

 

Usually worthwhile to run a good injector cleaner when getting O2 sensor codes. Can't hurt, sometimes helps:
https://www.yotatech.com/51228335-post5.html

 

How do you check the codes... my light came on today too... is there a key/on/off combo? thx

 

@ securekey:

to pull codes, you go to DIAGNOSTICS connector near your external fusebox (behind batt) and jumper connect terminal E1 and T. then go inside and turn on key and count flashes. my haynes manual had a chart of explanations.

i cleared the codes yesterday, drove all day without a relight, then this morning it popped right up. but it's pouring so i have to wait and see what came up this time around.

@ SB: i usually toss a Techron in once in a while; this past week i had a coupon for an o/c &rotate and they put in a bottle of Napa brand inj. cleaner; maybe the stuff shook something up, but i've been thru a tank of gas since.

@ABCDE: haven't noticed any change in idle behavior, idles smooth at 800, and it's too warm still around here to notice a cold idle warm idle change yet. the light does not come on immediately at start either. the other day it took a good hour of hiway cruise before it lit doing around 60; today it lit after 5 mins of traffic crawl right as i left home.

so no pattern. if i get a break from the rain i'll go see what codes it has now. hopefully not both but only one.

 

UPDATE:

i just went out to pull codes again, and i have 25 and 26 again! i cleared them one more time, confirmed they are clear (fast blink), and will drive later to trigger again. just making sure it's always both.
my first suspicion is AFM. any other suggestions?

 

mt truck is doing the same. i have a 92 v6 3.slow. This just started to happen. I'm going to try some injector cleaner, but i suspect it to be the AFM unit. I have a custom intake on my truck, so this could be setting it off. But funny this is i've been running this setup with the intake for the last 6 months. No codes.

 

SeaFoam it and see what you get, may help you out some. Then run some Lucas fuel treatment through it.

 

before i do anything, i'm going to wait for all this rain to clear. it's been going for days now. apparently my truck doesn't like it. on the way to mc.d's for lunch it starts making this clunk when it comes to a stop. doesn't require any speed do duplicate. a quick bump forward with the clutch, then step on the brake; when the inertia of the truck drops the nose down, THEN UP (to rest), there's a clunk. caliper? bj? i feel the knock in the floorboard sometimes. don't know, but not getting underneath to look. all of ATL is flooding.

 

i had the same problem a few months ago and got some MAF/AFM cleaner and sprayed the MAF down with it. my CEL came on the other day with 25 and 26, but it was right after i went through the car wash, so im thinking that might have triggered something.

 

jeez i hate it when people don't come back to report what solved the issue, and here i did it myself.

unfortunately, my old decrepit brain can't remember what solved this issue since it's two years ago already.

it's very possible that the culprit was a bad EGR causing the codes, because i remember having to replace that back then.

and the clunking i think was solved by replacing the front shocks.

i need a new memory. the one i got is shot.

 

This is drivin me crazy.....
I have a 95 4runner 3.0 4x4 and it has been very well maintained by the p.o.
I have reciepts for new heads and trans......
It only has 126xxx miles one it but man it runs rough!!!
It idles just fine in park....
But put it in drive or reverse and it idles horriable....
Feels like under load it drives fine but i have no clue as i am new to the 4runner world....
I just changed the plugs and wires and dist cap and button.... i did notice that the dist cap and button were prety rough on the inside...
My afm test out good...
What else should i look at?
Everytime i search i find the same thing with no resolve.....
Gunna look at my injector circut today....
Anything else i should check out while im in there?

 

I had code 25/26 on my 90' 22re. Ended up being the O2 sensor. If you look in the FSM there's a way to diagnose the sensor with a multi meter.

 

This is an old thread but undoubtedly it's still coming up in searches so just to clarify. Both of those codes are being thrown by the O2 sensor. Since they are in direct conflict with each other, your O2 sensor is either faulty or just plain old confused. Either way it needs to be either cleaned or replaced. I would replace it since it is a maintenance item but if it's midnight on a Saturday, take it out and clean it up good, clear your codes and see if that doesn't solve your problem.

 

Ok well im in the process of a body lift and crossover delete and building my exhaust so that will be part of it just gotta find the time to do it all in a weekend lol

 

Not quite. An intermittent vacuum leak (and a lot of other causes) can cause the exhaust to go rich and lean alternately. The O2 sensor is dutifully (and accurately) reporting the condition of the exhaust, and the ECM is trying to chase that O2 level by changing the mixture (by changing the injector open-time).

When the O2 level is so far out of whack that the ECM can't adjust the mixture far enough, THEN code 25 (or 26) is thrown. Both codes are stored, so even though the exhaust is not "simultaneously" rich and lean, you can trigger those codes one after the other and both will show up when you test for them.

In fact, it's difficult to get an O2 sensor to fail is such a way that it signals BOTH rich and lean, so having these two codes together does not (clearly) mean that the O2 sensor is at fault.

But it's actually easy to test the O2 sensor directly: http://web.archive.org/web/201003261...01heatedox.pdf Much more sensible (IMO) than replacing parts at random.

 

Scope103
That actualy makes sense.... as i did a compression check the other day and unpluged the coil pack to do so.... and then a few days later i got a spark fault code lol i was like wtf?!?!
But then i rememberd what i did....

 

Well said. That makes perfect sense. I let myself get too narrow minded in assuming that the codes were active codes vs. logged codes. I'm sure glad I'm not having to troubleshoot such an issue. That couldn't be an easy one to isolate, especially if you couldn't determine which code was thrown first and the amount of time between the two.

 

Ok so i replaced my afm and gave it a tune up.... replaced some vacume lines....
Awaiting a set of egr gaskets so i can do a egr delete and am planing on a PAIR delete aswell.... cant find gaskets for the PAIR....
And am as of now only gettin a lean mixture....
The reason i replaced the afm is someone was inside it at some point and fiddled with it.....
I am still idling funny in gear.... feels like a miss.... getting a new fuel presser pulsation damper and replacing the pcv valve aswell....
Would love to set my valve lash while in there but..... wow thats alota work so i might just bring the stuff i have to my buddys toyota mech and leave it with him a few days.....