FZJ80 Failed CO Emissions and Code 25

[IoN6]

I have a TOYOOBDI you can borrow to see the AFR and other values while driving around. Still crude, but better than codes alone.

How does it run >3000 RPM?

 

[FZJFirefly]

I have a TOYOOBDI you can borrow to see the AFR and other values while driving around. Still crude, but better than codes alone.

How does it run >3000 RPM?

It runs great other than it failing emissions and having a low idle which is why this is so confusing to me

 

[FZJFirefly]

Replaced the other o2 sensor with another 95+ as I didn’t want to spend $200 on one sensor but I think I have to buy the oem ones as this made it the worse emissions test yet


Purple is the one from this morning it also had the cel pop back up. Haven’t checked it but I assume it’s the same code 25

 

[FZJFirefly]

Okay just checked the code. It’s now a code 26 (Continuous Rich) any thoughts? Or is it still probably just an oem o2 sensor will fix?

 

[KC Masterpiece]

Wonder if you have an injector issue. Any idea when they were last cleaned or replaced?

 

[AdamKFarmer]

You don't need an OEM one, just a denso one. Look at the napa website, it lists the Denso model number, and then buy it from Amazon or Rock Auto

 

[FZJFirefly]

Wonder if you have an injector issue. Any idea when they were last cleaned or replaced?

Not a clue. TBH I doubt they’ve ever been cleaned or replaced

 

[FZJFirefly]

You don't need an OEM one, just a denso one. Look at the napa website, it lists the Denso model number, and then buy it from Amazon or Rock Auto

That’s the issue with the 93-94 they have different o2 sensors that have no aftermarket sensors which is why I put in 95+ ones following the post I have linked

 

[AdamKFarmer]

To be fair these are much more than the 96 ones.

 

[IoN6]

Have you checked the VAF? Not - take out the screws - check out? Does the vane move freely and return to fully closed?

 

[FZJFirefly]

Have you checked the VAF? Not - take out the screws - check out? Does the vane move freely and return to fully closed?

Just checked it. Opens and closes smoothly and closes fully. I’ve been messing around with my tpc and timing to try to fix my low idle can someone confirm their idle speed? I’m getting around 650 in park and around 500-550 in drive and it feels to low

 

[FZJFirefly]

To be fair these are much more than the 96 ones.

Yeah I spent $70 on the 95+ ones. Those ones are also more expensive then just buying oem sensors

 

[IoN6]

Do you have an FSM? Even the PDF version would likely suffice.

Have you checked for vacuum leaks?
How is in the soft intake tube from the VAF to the throttle body?
Have you checked the VAF per the FSM?
Have you checked that the fuel pump "kicks into high" >3000 RPM? <-- this was the most beneficial test I did

I have spent countless weeks/months/years in dealing with mine, some of which you can see in this thread.

 

[FZJFirefly]

Do you have an FSM? Even the PDF version would likely suffice.

Have you checked for vacuum leaks?
How is in the soft intake tube from the VAF to the throttle body?
Have you checked the VAF per the FSM?
Have you checked that the fuel pump "kicks into high" >3000 RPM? <-- this was the most beneficial test I did

I have spent countless weeks/months/years in dealing with mine, some of which you can see in this thread.

I have a pdf of what I think is the right fsm, I’ve replaced almost every small vacuum line including all but 2 under the intake manifold.

The intake tube isn’t that soft however I’ve sprayed carb cleaner all around it and into the flex joint and that didn’t affect the rpm at all so I assume there’s no leaks in that tube at least.

For checked the vaf is that just the ohm as it opens? I haven’t checked it other than seeing it closed and opened properly.

I don’t know how to check the fuel pump but right after I get past 3k rpm it noticeably pulls a lot better so I assume that part of the fuel pump is working

 

[RayRay27]

I know you probably dont want to hear this because it sucks to keep throwing cash at a maintenance issue but I would almost guarantee if you were to put in two oem 93-94 O2 sensors it would solve your problem. I had a similar situation where my truck was throwing a CEL 25/26 code, and as soon as replaced both with OEM sensors and retested my truck it passed no issues.

94 80 O2 sensor wire - harness side

So I had a check engine code 26 pop up the other day. Truck started to run like poo-poo when idling or stopped. It's been a while since I replaced both sensors so I picked up a set from Stevinson today and started diving into it. Yes i did diagnose a bunch of other potential O2 issues prior...

risingsun4x4club.org

 

[FZJFirefly]

I know you probably dont want to hear this because it sucks to keep throwing cash at a maintenance issue but I would almost guarantee if you were to put in two oem 93-94 O2 sensors it would solve your problem. I had a similar situation where my truck was throwing a CEL 25/26 code, and as soon as replaced both with OEM sensors and retested my truck it passed no issues.

94 80 O2 sensor wire - harness side

So I had a check engine code 26 pop up the other day. Truck started to run like poo-poo when idling or stopped. It's been a while since I replaced both sensors so I picked up a set from Stevinson today and started diving into it. Yes i did diagnose a bunch of other potential O2 issues prior...

risingsun4x4club.org

Honestly I hope it’s just that simple and I also just unplugged one of the new sensor and the idle got a bit better. So I’m going to just order new sensors tomorrow and hope

 

[FZJFirefly]

Okay it’s most definitely the o2 sensors. Just bought a multimeter and took a reading of the o2 sensors and got a reading from one at 13.5ohms @ 68 degrees air temp. They should be around 5-6.5 as stated by the fsm

 

[MileHigh80Guy]

You've done everything so far but the O2s and diag'd pretty damn well, but this shit is so frustrating. Stick with it!




While you're in there, test all leads on the harness from O2 to ECU for resistance/continuity. The driver side one goes over the trans, up the intake manifold and along the firewall before it goes to the ecu. The passenger side, the one 6 inches from it, goes 3 ft up the fender to the ECU... SMDH... Engineers...
Lots of room for breaks, corrosion...

---

Hopefully this helps someone in the future, between the troubleshooting here and my "adventure"...

That was not only my issue, but the O2s were also bad contributing. Straight up not a good time.
Also, I found it easier to remove the downpipes from the manifold, then the rear most CAT to exhaust bolts, also, less than fun. Grab some new OEM gasket for the downpipes to manifold, cat to exhaust and maybe even 2 more from the cat to downpipes, PLUS the O2 gaskets. When the pipe is removed, you can get a much better game plan on removing the O2 nuts based on how they look, mine were not great.

THAT SAID, I did all this, plus other shit that was less than ideal, and I just passed emissions yesterday.

Started with FAILED at 7.9 NOx, 1 Unknown intact cat, one empty fake cat, bad O2s and wiring with both O2s codes and more than a few crusty, broken harnesses and vacuum lines, AND a leaky AF PAIR VEIN thing... Fixed all that.

Mine failed on NOx though, got a 4.1 out of 4 on my 93
That was with:
2 new OEM Toyota O2s (the new part number)
Rewired them (wires were FUBAR)
1 Non CARB cat (which replaced the hollow fake cat from the PO, it was an out of state car)
1 possibly an old OEM one (it was in there already)
OLD OIL
New spark plugs/wires
Timing confirmed
Smoke test with confirmed no vac leaks
10 minute drive with one bottle of heet and 1/3 of a tank of 87 (on top of 1/8 of 2 year old gas), cool day < 70*.

5 Days later, it passed with a 3.01

My formula was all of the above plus:
45 minute drive ECT and OD OFF
timing confirmed
oil change
New cap and rotor
1/3 tank of 87, 1.5 gallons of E85, 2 bottles of red heet.
(The last 2 may not have been required, the (presumably non-CARB) cats likely weren't hot enough, bad old gas remnants and dirty oil at the 4.1 test, but I was over it...)


Im in West Arvada if you wanna reach out too.

-CJ

 

[FZJFirefly]

Okay well now I’m just confused. It got better than the purple one but it’s still worse than the yellow one . Also I noticed they turned overdrive off when testing it would that cause it to have more emissions due to higher rpm or is it negligible?


O2 sensors helped the idle a lot but still feels a little low as well.

Is it time to bite the bullet and replace cats?

 

[RayRay27]

1. I dont think its a cat issue, your NOx reading is low.
2. What do you mean by purple vs yellow?
3. What size tire are you using to test with?
4. Are you throwing any codes again?
5. Have you disconnected your battery recently? If so you may need to drive the truck again for it to re-learn or reset the emissions system. This goes double for replacing the O2 sensors. You may need to drive it for a bit so the system to adjust.