FZJ80 Failed CO Emissions and Code 25

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sjpitts said:
Maybe I am misunderstanding what you did --if what you did was install a 95-97 O2 sensor on a 94 --- but in my opinion you screwed up here. The 95-97 O2 sensor is not compatible with the 93/94 computer, and changing the connector does not fix it. The issue is not just that the connectors are different -- it is the ohm values the sensor provides during operation.

So maybe I misunderstand, but if it were my I would source the correct 93/94 O2 Sensor (and switch back to the old style connector).

Preferably OEM Toyota if you can find it. The OEM Toyota sensor you can use for both locations on the 93/94 is 89465-69115.

And while you are at it get two of those sensors.
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You’re right with the values. Just bought a multimeter and tested the ohm value of the new o2 sensor at 13.5ohms when the fsm states 5-6.5ohms. So I’m going to order those o2 sensors and hope that fixes the majority of my issues
 
BTLSHP said:
I can't help you. The Cats are a big expensive project and they are also pretty robust. The best test I know is an infrared thermometer. Check the from of a hot cat and the back, the back needs to be something on the order of 100 degrees hotter. If the front and back are the same temp, you have a Cat issue. I simply run too many old cars with original Cats to focus on them as a primary fault, unless they throw a unique code. I had a P0425 on my wife's Lexus that I ignored right up to the test. I fixed an exhaust leak in the flex pipe a foot away and after a week or so the P0425 disappeared.

There is a ton of info on here about the IAC and in the FSM. I never touched mine beyond confirming the resistance on the pin outs.

I do not think adjusting the IAC is all that difficult, but I recall taking it apart carries risks.
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I tested the cats with a heat gun after that most recent fail and it was about exactly 100 degrees hotter out of the back then exhaust going into the cats
 
FZJFirefly said:
You’re right with the values. Just bought a multimeter and tested the ohm value of the new o2 sensor at 13.5ohms when the fsm states 5-6.5ohms. So I’m going to order those o2 sensors and hope that fixes the majority of my issues
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I do not recall if I have replied to this post about the OHM resistance on your O2 sensors. But I was having very similar issues and checked the VAF and it was GTG, then checked the O2 sensors the resistance was way off like yours were. I replaced mine with Bosch O2 sensors, against the recommendation of others on this forum but Bosch has been around for years. I have had to do 2 emissions test here in AZ and pass every time now.
 
OffRoadScott said:
I do not recall if I have replied to this post about the OHM resistance on your O2 sensors. But I was having very similar issues and checked the VAF and it was GTG, then checked the O2 sensors the resistance was way off like yours were. I replaced mine with Bosch O2 sensors, against the recommendation of others on this forum but Bosch has been around for years. I have had to do 2 emissions test here in AZ and pass every time now.
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I read your Bosch Sensor post with great interest and fantasy's about what I could do with the money saved. I chickened out.

I wonder if the recent court decisions rejecting the 10% tariffs means we are back to the old ways with Partsouq and Japan4x4?
 
FZJFirefly said:
I tested the cats with a heat gun after that most recent fail and it was about exactly 100 degrees hotter out of the back then exhaust going into the cats
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So, I think you can tick those off of your risk list for now. I have no idea how mine would have been replaced. The flanges and bolts were one. If you are in the FSM near the O2 Sensor pages is the test procedure for the VAF. I went no further than confirm the resistance. The next step would be to gently clean the vanes and their pivots with air. Not me.

Good luck
 
BTLSHP said:
I read your Bosch Sensor post with great interest and fantasy's about what I could do with the money saved. I chickened out.

I wonder if the recent court decisions rejecting the 10% tariffs means we are back to the old ways with Partsouq and Japan4x4?
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Just checked Amayama and they are including the fees when you proceed to the cart to check out.
 
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?
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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?
 
I would not jump into cats. You have a decent temp differential there based on my '94 a year ago. You have something wrong with your idle, any signs of a fuel pressure issue/injector leak?

What my daughter did was go back for her "free" test and they directed her to the State help lab. The guy there was incredibly helpful.

Sorry you are still in this mess. Ours had been test free for 6 years before getting to CO. I was biting my nails.

Sorry I do not Know how to rotate this. It is one of our failed tests. Note our CO line on the right side of the graph was up and down, where yours was a flat line. Curious.


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BTLSHP said:
To be clear, it is a '94 he is trying to get through and so it is x2.

Curious, have we checked the timing is at 3 degrees yet?
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fair point that does make it a little more tricky, and carb might be his only option because you cant modify the location of the cats. but yeah regardless aftermarket cats dont last long and at his mileage there is a high chance for colorados standards his oem cats are done.
 
lastresort576 said:
fair point that does make it a little more tricky, and carb might be his only option because you cant modify the location of the cats. but yeah regardless aftermarket cats dont last long and at his mileage there is a high chance for colorados standards his oem cats are done.
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Perhaps I cling to closely to his reported 100 degree temp difference front to back in the cats. Something is going on ...

I think weld in replacements are available. On ours the nuts/bolts look like a molten bloob. I have zero clue how they would come off short of a saw.
 
BTLSHP said:
To be clear, it is a '94 he is trying to get through and so it is x2.

Curious, have we checked the timing is at 3 degrees yet?
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Yeah I set the timing a few tests ago and checked it before this one.

The cats were replaced in Utah in November of 2020 so they’re likely non carb compliant so that’s why I’m assuming it’s just time to just get cats installed
 
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FZJFirefly said:
Yeah I set the timing a few tests ago and checked it before this one.

The cats were replaced in Utah in November of 2020 so they’re likely non carb compliant so that’s why I’m assuming it’s just time to just get cats installed
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They dont have to be Carb compliant to pass in CO. You just cant buy fed compliant cats in CO. However, theyre old enough to have gone bad if not oem from what ive seen.

Give a parts store on the border of a neighboring state a call and have them order some up for you and go pick them up...or spend ballpark twice as much for the carb ones.
 
Lots going on here but have you sorted out the low idle yet? I struggled for a long time with a low idle (400rpm when warm) and the only solution was to dig in and really sort out the underlying issues. Now its a solid 650rpm on the dot, you can set a cup of coffee on the valve cover its so smooth.

This is a total shotgun approach. Hopefully you pass emissions along with having a perfect idle after doing all of this. The time cost is high but the parts cost is low and in the end it will definitely run a lot better.

- Disconnect the battery
- Pull the upper intake manifold, replace all of the vacuum lines under there (regular OEM works just fine), replace the fuel filter, even pull the injectors and have them serviced.
- If needed replace the coolant hoses under the upper intake (PHH, throttle body coolant hoses)
- Check all of the vacuum switching valves (VSV) per the FSM
- Open the wiring harness loom where it passes the EGR pipe and inspect for shorts or damage to the insulation, repair if needed. Secure the wiring harness away from the EGR pipe to prevent future damage from heat.
- Deep clean the throttle body including the idle control valve passage. Confirm it closes all of the way.
- Test the idle control valve per the FSM (stepper motor)
- Adjust the throttle position sensor per the FSM, with a multimeter (this is crucial to achieve a 650 rpm idle)
- Adjust the throttle cables per the FSM
- Replace the PCV valve and check that the PCV hoses are in good condition
- Check that the oil fill cap seals correctly, if not replace (this can cause a vacuum leak if not sealed)
- Check the 02 sensor wiring and replace the 02 sensors if they have not been done (OEM or equivalent)
- Normal tune up items such as cap, rotor, plugs, wires, air filter, check the timing (sounds like you've already done these). After emissions bump it up to 7-8 degrees.
- If there are leaks in the valve cover gaskets (the cover and the spark plug tubes) get those sorted while its apart

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ZackR said:
Lots going on here but have you sorted out the low idle yet? I struggled for a long time with a low idle (400rpm when warm) and the only solution was to dig in and really sort out the underlying issues. Now its a solid 650rpm on the dot, you can set a cup of coffee on the valve cover its so smooth.

This is a total shotgun approach. Hopefully you pass emissions along with having a perfect idle after doing all of this. The time cost is high but the parts cost is low and in the end it will definitely run a lot better.

- Disconnect the battery
- Pull the upper intake manifold, replace all of the vacuum lines under there (regular OEM works just fine), replace the fuel filter, even pull the injectors and have them serviced.
- If needed replace the coolant hoses under the upper intake (PHH, throttle body coolant hoses)
- Check all of the vacuum switching valves (VSV) per the FSM
- Open the wiring harness loom where it passes the EGR pipe and inspect for shorts or damage to the insulation, repair if needed. Secure the wiring harness away from the EGR pipe to prevent future damage from heat.
- Deep clean the throttle body including the idle control valve passage. Confirm it closes all of the way.
- Test the idle control valve per the FSM (stepper motor)
- Adjust the throttle position sensor per the FSM, with a multimeter (this is crucial to achieve a 650 rpm idle)
- Adjust the throttle cables per the FSM
- Replace the PCV valve and check that the PCV hoses are in good condition
- Check that the oil fill cap seals correctly, if not replace (this can cause a vacuum leak if not sealed)
- Check the 02 sensor wiring and replace the 02 sensors if they have not been done (OEM or equivalent)
- Normal tune up items such as cap, rotor, plugs, wires, air filter, check the timing (sounds like you've already done these). After emissions bump it up to 7-8 degrees.
- If there are leaks in the valve cover gaskets (the cover and the spark plug tubes) get those sorted while its apart

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After the ecu got used to these oem sensors the low idle came back in full force but at least not it doesn't shake and feel like stalling so this is really helpful!

I've already replaced all but 2 of the vacuum lines under the intake manifold when I had the throttle body out to clean it the IACV and to change out the valve cover gasket.

I was also already planning on pulling vacuum on the TPS tomorrow and getting that adjusted as I just had turned it to about where it was before I had started adjusting it as it only made things worse when I was messing with it.

If all else fails I'll pull the intake manifold and investigate everything under it but hopefully I can sneak by without it as it seems like a major pain when I was doing vacuum lines previously
 
Well just got done adjusting the tps and it made no difference to my idle so doubt that was a major contributor to emissions.

Might just send it to a shop at this point unless anyone has a solid lead as I don’t have time nor the money to keep shotgunning parts only to make it worse
 
This may appear an odd question, but does your Instrument panel gear position indicators show what gear your in?
For the 93-94 model years, the Park Neutral Safety switch is how the transmission and engine controllers know what gear your in. On my 94, the Park neutral safety switch connector just below the PHH was corroded badly, to the point the terminals were "dust". None of my instrument panel gear position indicators worked, my backup lights did not work, and I had a really erratic idle, (usually high). Replacing the park neutral safety switch on the transmission and repairing the body side connector cleared up those issues and fixed my erratic idle, and it drove better too.
It also improved my idle emissions. I had no codes.
For the 95+ model years Toyota used gold plated connectors, not tin plated, so they are less susceptible to corrosion.
 
getsthr said:
This may appear an odd question, but does your Instrument panel gear position indicators show what gear your in?
For the 93-94 model years, the Park Neutral Safety switch is how the transmission and engine controllers know what gear your in. On my 94, the Park neutral safety switch connector just below the PHH was corroded badly, to the point the terminals were "dust". None of my instrument panel gear position indicators worked, my backup lights did not work, and I had a really erratic idle, (usually high). Replacing the park neutral safety switch on the transmission and repairing the body side connector cleared up those issues and fixed my erratic idle, and it drove better too.
It also improved my idle emissions. I had no codes.
For the 95+ model years Toyota used gold plated connectors, not tin plated, so they are less susceptible to corrosion.
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Yeah it does just the D light is out like most
 
Definitely double check your timing.

Also @BTLSHP is right on the money, I'm betting. The IAC on our 94 failed the FSM testing, as did the throttle position sensor (TPS). The idle in our rig was all over the place due to those two components failing. Replaced both, and advanced the timing to 6 degrees (something that you could do after you pass emissions), and it runs great.

Text the above components. If they are in spec, then they aren't your problem, and you've just saved yourself some money. If they are out of spec. replace them. Lastly, question... did you pull and reseal your distributor (new o-ring)? If you did, it's possible that upon re-install, it wasn't clocked properly (and that is something that's very easy to do).

I posted up in another thread earlier where a new owner was having similar problems (not the emissions part but starting/and idling). Haven't owned our '94 all that long, but if the IAC and TPS are original to your rig, there's a good chance that they are failing due to age.

BTW - the IAC for '94s is NLA. You can buy the IAC for the '95-'97 and it will work just fine.
 
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