Can You Solve This CEL O2 Sensor Riddle?

Long story short, my cats got stolen and I bought&installed long tube headers, air pump delete, and 12 hole injectors along with brand new spark plugs OEM off Amazon.

When I got the car back after all parts installed simultaneously it ran perfectly other than a secondary O2 sensor CEL due to not having them hooked up.

After a week of driving, all these problems rose. Misfiring, insane raw fuel smells in the cabin and especially when pumping gas, I'm talking raw gasoline fumes that sting your nose. CEL would flash. Bucking, stuttering, plumes of white smoke.

After a while of continuous use in this state, I got the O2 wire extended and hooked them up along with defoulers (post cat)vat.

The plumes of smoke have gone away but I'm still having the other symptoms.

I purchased an OBD2 reader and found I had the P0051 CEL which is the primary O2 sensor pre cats.. I swapped the driver and passenger side O2 sensors and checked the code and the code changed from P0051 to P0031.AHA! BAD O2 sensor (heater circuit). Upon inspection, the bad O2 was bent.

I replaced and installed the new sensor and I still have the CEL along with TRAC and VSC lights. I've tried deleting and resetting the codes multiple times. Disconnecting the battery, but the lights and faults remain.

Do I need to do a lot of driving for the drive cycles to complete so the lights go away? Here are the pics I took off the reader.

 

Do you have front cats? Those are key for fuel trim.

 

I have no cats at all. Do our cars have two or four? When I looked underneath two sections of exhaust were cut off, one each side along with the wires.

Either way, the longtubes delete the cats. I'd figure that the secondary post o2's would be the problem. But its the front/pre cat/upstream/sensor 1/closest to the engine (whatever you want to call them) which are triggering codes.

Do you think that this one lonely CEL is causing all these failing-EVAP like symptoms along with these random misfires? Randomly 2, 4, 6, and 8 would misfire which is all on the same bank (same bank as failing o2 sensor). The misfiring and the codes themselves will go away and solve it's own issue with only the P0051 or P0031 heater circuit code remaining depending on which side I had the failed sensor on.

 

1) I would get rid of the Amazonian spark plugs immediately. Buy them from anywhere other than there or e bay.

2) Your front o2 sensors should handle the air fuel mixture. It is strange that replacing the bad one (good diagnosis btw) would lead to other problems. Did you disconnect your battery to clear the codes after replacing the sensor? If not, try it.

3) out of curiosity, what are you running for exhaust after the long tubes? Do you have a y pipe or x pipe or even duals with an h pipe?

 

My bad, front o2s are for the fuel trim, and located in the collector on the headers? Or one of the pipes?

 

I am using the scan tool device to reset the codes. Do you recommend doing the battery method as well?

I am going to swap these plugs because I'm guessing they're fakes.

Only the headers and y pipe are aftermarket, rest of exhaust is stock.

Yes, on the collector of the headers. Both of them followed by the secondary o2's (post cats) on each side.

 

These are the plugs I bought. It appears they're Denso brand. Sold and shipped by Amazon. Any reason to have fake concerns or are they legit?

$9 Denso (3297) SK20R11 Iridium Spark Plug, Pack of 1

https://www.amazon.com/gp/product/B0012Q4IPY?ie=UTF8

 

https://www.driven2automotive.com/blog/how-to-spot-fake-denso-iridium-power-spark-plugs-2017/

If clearing the codes with the reader doesnt work, clearing by disconnecting the battery couldnt hurt? Disconnect, touch the cables, and wait 20-30 minutes? Maybe someone will chime in with the ‘proper’ procedure.

have you checked for any exhaust leaks at the gaskets?

 

Anything 'fulfilled by scAmazon' is at risk of being a fake. Actually, anything that originates at one of their warehouses has risk of being fake, because the inventory is at risk of being mixed. Just avoid the hassle. Never, ever, ever buy auto parts off scAmazon or fleaBay. Neither's systems allow for them to properly vet every piece of inventory they stock, they don't have the ability to scrutinize inventory. Period. And they have no skin in the game if you get duped, they have no legal recourse if you get boned, there is no consequence for them, period. Just don't put yourself at risk. Buy from your LAPS, from RockAuto, from Summit Racing, or some other vendor that actually vets their inventory and isn't well-known for selling counterfeits. They have to care about their brand and reputation.

 

Are you running any sort of o2 simulator or defoulers on the rear o2 sensors?

You can find a Denso store through Amazon but I would steer clear of them at all for spark plugs. For one we have seen pretty frequent fake or low quality plugs from there. Some people reported very bad gaps on them. Also amazon doesn't treat things with care and you don't want plugs that have even dropped. Hate to waste money but I really would throw those out and either buy from Toyota or Rock Auto or some other reputable auto supplier.

 

Yup, got defoulers, and my plugs came all messed up in the package. Little cartons squished and plugs were loosely in the package.

I do have a tiny exhaust leak past both o2 sensors.

Just did a 30 minute battery reset, all the faults are still there. Did a 32 mile drive and I noticed that the butter smooth idle is back along with the smooth shifts. It's not holding gears forever anymore and it's no longer lurching when it shifts.

Perhaps I just have to keep driving and trigger all the drive cycles? The scanner still shows "not ready" for the evap, secondary air, o2, and cats.

 

I would still get rid of the Amazon spark plugs to be safe. I almost destroyed our RAV4 with counterfeit Denso plugs.

https://www.tundras.com/threads/counterfeit-denso-spark-plugs.64225/

 

Yikes!

I did some live data monitoring. Does this evap pressure look right?

Also says OL-fault for fuel system 1 but fuel system 2 is CL.

Bank 2 sensor 2 O2 output voltage only at 0.055 where has bank 1 sensor 1 is at 0.7.


When idling and giving the engine a rev, the engine has a slight judder and rims fall lower than idle when they come down and it takes a second for the engine to work up and get back to idle rpm.

 

As in P0051 or P0031, C1201 ?
Are TRAC and VSC lights still on ?

"not ready" will continue to show if you still have those A/F sensor codes and once fixed, should clear the O2/Cat readiness monitors. Speaking of the drive cycles related to readiness monitors, I'll attach a pdf concerning those monitors from FSM. I'll also assume that you have an 05-06 given the mention of Secondary Air Injection. Evap in particular can be lazy in getting ready if certain criteria is not followed.

What year/model/type Tundra in case it helps ??

Similar to the plug comments by folks, where did you purchase sensors and are they OEM from reputable source ?

As for the A/F and O2 sensors voltage difference, we are dealing theoretically with 0-1 vdc. The A/F sensor with eng operating temp normal at idle when graphed will appear as a sine wave and will vary from say .055(lean) to .8(rich) vdc.
The rear O2's with eng operating temp normal at idle will be a solid line on graph with minimal fluctuation. The below pic is after me changing a rear O2 sensor. The sinewave is A/F sensor that went from a high of .820vdc(rich) to low of .055vdc(lean). The solid line is the O2 sensor @ .047vdc.

 

^^Thank you. The o2's were purchased from O'Reilly. The plugs from Amazon. I will test and see if my graph reads that way. My truck is an 05 Sequoia. I swapped the relay with another one and the relay is not the issue.

I somehow forgot that I also had the timing belt and water pump replaced. After doing further research there have been documented cases like mine with multiple misfires on 2,4,6,8 like mine randomly and it's possibly due to the timing belt being slightly off.. Man oh man I sure hope that's not the case. I don't have the patience to take the cover off, check, and adjust which would be something I've never tackled before.

 

Thanks, that definitely helps.

Scratching my head but I don't see how a timing belt being off would give your results mentioned above..

That aside, you didn't by chance get bad gas somewhere at an elcheapo place. I still have thoughts an AF sensor is part of this problem. I also know back pressure will cause misfires but you're saying cats are deleted correct ?

 

I'm a noob when it comes to timing belts and timing in general, so I wouldn't know why either but doing some google searches on this platform shows that this is a possibility. As for gas, can't be because I pump at QT or Costco or Shell. Same gas stations I've always pump at before these problems.

I'm purely dumbfounded at this point. Cleaned MAF, Throttle Body, and PCV yesterday as well. Still getting the O2 light and not ready status. I'm noticing a very slight stumble in idle. So slight it's barely noticeable. I do notice that while under constant throttle the RPMs have a tiny dip/hiccup. Also barely noticeable and 9/10 people driving the car wouldn't notice or chalk it up to being an old car.

 

Clean the throttle position sensor?

did you double check the header flange area for leaks? And the block off plates?

Im just winging ideas out there. The vvti engines are too complex for my walnut brain to fathom. Is it still running rich at .7v?

 

That .7vdc was an AF sensor reading at that exact moment in time and while it is indeed a valid number, one has to see a graph of the AF sensor and hope it is a rich to lean of approx .8 - .1 vdc sinewave representation. One can also view the numbers without graph by watching the AF sensor reading go full rich to full lean approx once every second.

 

I've been busy over the weekend and haven't been able to do more OBD diagnostics.

Here's a video if a strange sound coming from the engine while idling. Haven't heard this before.

https://vimeo.com/698071744

 

For videos to work... you have to upload to YouTube, a d then post a link here.

Also, get rid of the spark plugs. Buy from a local place, rock auto or a dealership that will mail you the plugs.

What brand were the 02 sensors you installed? Try using Denso. These trucks don't typically like any other brand of sensors. The readouts from the sensor to the computer are not always in a format the computer can understand so it throws a code.

Like trying to speak French to someone speaking Japanese. Not a lot is understood so there is general confusion.

However using Denso sensors will eliminate that possibility so the computer and the sensor will both be speaking Japanese

 

^^ Denso everything.. Video doesn't work for you?

 

Video worked for me. How’d you do it? Uploading to youtube isnt hard, just extra steps.

 

I used vimeo, I stay off YT for anonymity.

Took some pics of plugs and coils. Plugs have this white, gray bluish layer on them. Comes off with a some rubbing. One of the coils was brown compared to the rest with one other kind of brown.

Did a search for how to spot fakes, tough to tell with them being used. Going to buy new ones tomorrow.

Used electric parts cleaner on the coils and harness

 

White on plugs is a sign of heat. A quick search shows you have the right heat range. When a cylinder leans out, it burns hot. Were those on the even # side?

 

Passenger side which I believe is bank 1 on this truck.

 

id call that bank 2. But who knows…toyotas are weird sometimes.
Theres 3 different denso iridium plugs recommended by rock auto, i wonder if the heat range is different… lemme dig around on here and see which plugs i used.



bummer. My pics didnt show the number, and im not at home where my spares are. But they were identical to the ones i replaced em with. Looks like the last 2 are ‘gp’

 

Just the opposite....Driver Bank 1, Pass Bank 2 like @Sirfive pic is showing.

 

I can tell you after my most recent valve cover gasket overhaul, my cylinders 4 and 6 had similar looking coils, with possible heat/burn-in signs. I suspect I may see similar on my 4 and 6 plugs when I do my plugs between now and next oil change.

 

Are the burnt/hot coils cooked or still good? Currently waiting on the NAPA truck to deliver my stuff. Ordered the TT Denso plugs this time.

Also, so much contradicting info out there. Not you guys or anyone in here per say but those diagrams clearly show that bank 1 is driver side however my car says B1 is passenger and B2 is driver side. Even saw a youtube clip where it was the same on someone elses truck.

After I install new plugs, I'm going to check all wires, relays and fuses again then do an OBD diagnostic.. Also going to reswap both upstream O2's. If all else fails, this truck might go visit the crusher.

In all honesty. THANK YOU guys for your help and assistance. Amazing and incredible group of knowledgeable guys. This forum is one of the last few out there that's still a forum.