1999 5vzfe TRD supercharger URD 7th California emission

I feel like I'm always chasing something with this car.

Using torque pro my o2 sensor1 (a/f sensor) voltage pretty much only stays at 0.6v. From what I've mostly read this means the sensor isn't working as it should be oscillating between .1 and .9. but i've also read something about a/f sensors specifically that they have a different behavior. I dont remember the specifics on that. Anyways my o2s1 voltage only bumps higher or lower than .6/.7 for a second when changing load for example when downshifting for a lane change.

My o2 sensor2 voltage seems to correctly oscillate between .1 and .8

On top of what I gather to be a bad a/f sensor I hit my catalytic converters with a laser temp reader and they are both colder at the outlet than the inlet which I understand to mean they're not working. I'm going to take the reading again later after a proper drive to get the cats heated up. These temps were taken after only a couple minutes of idling.
EDIT I took catalytic converter temps again after a good drive and it looks like the first cat is lighting off and the rear cat is not. First cat's outlet is >10% hotter than the inlet. The rear cat's outlet is slightly cooler than the inlet.

My main question is this:
Does my o2 sensor 1 voltage constantly sitting at .6v mean it's not working? Or is that normal behavior of a cali emissions a/f sensor?

Edited original post to add this info: I took catalytic converter temps again after a good drive and it looks like the first cat is lighting off and the rear cat is not. First cat's outlet is >10% hotter than the inlet. The rear cat's outlet is slightly cooler than the inlet.


Still trying to understand if the a/f sensor needs to be replaced

My first question is, what problem are you trying to solve? Do you have a P0420 Check Engine Light? Your upstream sensor values look normal. Sometimes the upstream values are reported on a 0-5v scale, and some are reported on a 0-1v scale. Unlike a narrowband sensor, the Toyota wideband AFR sensor does not generate voltage like a narrowband sensor. Instead, it generates current. The ECU looks at the strength and direction of the current generated by the air-fuel ratio sensor to determine what the AFR is. Then, it reports a voltage value that corresponds with the AFR it sees from the sensor that you see in your OBD scanner. This chart should help you make sense of the data you’re seeing for the sensor.

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I have no CEL currently but once in a while a P0420 does come on. Mainly looking into my high LTFT (~14%) at idle and low throttle and more recently a stumble that happens at low-load acceleration. All of my fuel system components are pretty new, MAF is new denso, spark plugs are new denso ik22s, wires are 20k mile NGK's, front a/f sensor is a new "denso" (from Amazon, but i guess it's working), theres no burning oil or coolant, what I think I'm left with is vacuum leaks, exhaust leaks, and o2 sensor.

Yesterday I didnt find any vacuum leaks during my smoke test but I've identified very small exhaust leaks at the o2 sensor flanges by blowing air through the tailpipe and spraying soapy water on the joints. Very tiny stream of bubbles coming out. I'll clean those surfaces and replace the gasket and nuts.

I did, however, find a large exhaust leak at the flange just AFTER the rear o2 sensor. I've ordered the parts to replace the gasket and hardware as I've read that even a leak after the o2 can affect the sensor's reading and this flange is just a couple inches directly after it

I'll clean the MAF and replace the dirty air filter asap as well

seems your making logical steps .good luck ,let us know how it goes after repairs

Also most obd scan tools don't have a fast enough sample rate to see the true values of the o2/afr sensors. Which is why the majority of fsm's tell you to pin out the sensors connector, either with a o-scope or a volt meter. But a good o-scope is pricy, so usually cheaper to just replace the sensor.

But just looking at the rear sensor voltage it should be a flat line. But also having an exhaust leak inches away and at the o2 can cause that too. As the exhaust gases exit in pulse waves, positive pressure in front of the wave and vacuum behind. So every time a wave passes is sucks in air.

Also are they original cats? Exhaust system parts have a lifespan. It's a 24+ year old car, if they lasted this long that's awesome and you are lucky.

I'd be suspect of anything "Denso" or "NGK" if you got it from Amazon or eBay. They are FILLED with knock-offs.

OEM (from a local dealer or online dealer), RockAuto or a local parts store are all good options to get reliable parts.

-Charlie

2 new oem sensors are on order from Toyota. Even if the a/f sensor seems to be in working order I'm just gonna rule that out for sure.

As far as I know they are original cats. I've got like 14 years of service history for this car and no records of them being replaced. According to my temp gun the front one is operating (output hotter than input) but the rear is not so much (output only slightly hotter or equal to input) which is a bit confusing for me because I thought the front would go first if anything.

We'll see how it goes when parts come in this week

That large exhaust leak you mentioned, curiosity has me thinking I'd fix that change nothing else.
Had cat to muffler flange leaking condensate lot's mild temps cold start. Fixing that
seat O the pants noticed operating difference no problem no need to dig further.
Your problem mine I'd have to scratch that itch do the simplest fix for the hell of it.

Yes, I agree. P0420 code is often caused by exhaust leaks - even very small ones. Start there for sure and potentially save a bucket of money. I have both original cats and created and solved a couple of P0420s when installing and experimenting with a Magnaflow cat-back exhaust system and creating post-cat leaks by leaving clamps too loose. We did a group buy here and got them for right around $500 shipped. The price has gone up quite a bit!

Being supercharged, do you have an AFR gauge?

My location good chance OE pipes/shells outlasting the guts.

I fixed the exhaust leaks, replaced afr/o2 sensors, cleaned MAF, and replaced the air filter with no improvement. Also double-checked my spark plug gaps and cleaned any corrosion on the plug wire to coil pack connections (those caused a stumble for me in the past)

The rear cat is def dead tho, the output is consistently the same temperature or slightly colder than the inlet. I've read that the output should be 10% up to 100f hotter than the inlet if the catalyzing process is happening correctly.

I did find a vacuum leak though, from a fuel injector
During a smoke test I saw some leakage from under the supercharger but couldn't tell from where so I turned the smoke off and changed to soapy water with the air still running and found the bubbles.



The bolts that hold the fuel rail down are as tight as I'd possibly go on aluminum threads. The injector doesn't have up and down play but it can turn easily by hand with everything still bolted. It got fresh Injectors and O-Rings last year from Motorwest Performance, I don't think the o-ring folded over as I used the provided grease during the install, but they were suspiciously easy to pop in. I'm gonna send them the video and see if they have any useful tips or advice.

Besides that I'm still considering also pulling the cat down and cleaning it out. Couldn't hurt if it's already dead.

Well that sucks. But a moderately easy fix. I have had that issue before on my miata. Kept ripping o rings, until I got some viton orings. That air leak is more then likely the lower o ring is either torn or to small and not sealing. Keep us updated please.

Judging from the video, I’m inclined to think it’s not the oring, but the fat grommet thing that sits on the bottom of the injector and seals it to the head. If you pull the injectors out and and look at where the bottom is supposed to seat, you’ll see some open ports that are part of the air assist system. If the big grommet thing is leaking, those ports will suck in unmetered air causing the high fuel trims.

Advance Auto seems to have the injector seal kits, p/n AS037.

Looks like Oreilly’s has it as well, p/n 158-0893.