Major sputtering problems after installing brand new O2 sensors in 2001 Celica

Maintenance/Repairs
1

My fiance’s 2001 Toyota Celica GT had a check engine light on for faulty o2 sensors for a long time and we just now got around to replacing them. Car was running perfectly fine on old sensors, good gas mileage and everything, we just wanted to get rid of the check engine light in hopes to sell the car.

So I bought the matching upstream and downstream O2 sensors from Amazon (Denso brand) and went to install them and didn’t have any problems doing so.

Then when I thought the job was done I turned on the car to find it sputtering, backfiring, and barely able to keep staying on without me throttling it. I have heard that some cars need some time to adjust to the new O2 sensors so I keep restarting the engine, idling it, throttling it, driving around in circles slowly, but nothing is working.

After a half hour of trying to get it working by doing this I decide to switch back to the old O2 sensors temporarily thinking I just got a bad new O2 sensor from the manufacturer.

Only thing is after switch the old ones back on the car still sputtered like crazy for a while until it seemed to be running fine. We drove the car about 2 miles reaching up to 60 mph and had no problems. Fast forward 2 hours later and the same problems are back and the car is barely running.

What in the world is going on!

2

My first question…If the vehicle was running perfectly well then why did you replace them? O2 sensors are not something you replace for the heck of it.

It might just a bad one. After you put the new ones in were there any codes?

3

Look around the area you worked and see if you may have knocked another sensors connector lose. Disconnect the battery for a few minutes and see what happens. If it is still running poorly check to see what codes you have.

4

What was original code? Too Rich? Too lean? That is not a code for a bad sensor, it is an issue that the sensor detects. Perhaps the code was for defective heater circuit in sensor? Don’t know

5

If the engine was cold when you started it after replacing the O2 sensors, the O2 sensors aren’t the problem.

When the engine is started cold, the computer is in the open loop mode. This means the computer makes adjustments to the engine from the signals it receives from the coolant temp sensor, the throttle position sensor, the MAP/MAF sensor, and the crankshaft position sensor.

It’s not until the engine warms up to a certain point where the computer goes into the closed loop mode, and makes adjustments to the fuel trim from the signal it receives from the upstream O2 sensor.

Tester

6

I don’t have the codes written down anymore and the car is at my Fiance’s parents, but putting in the new O2 sensors got rid of the codes while the old ones brought them back. I do remember it saying something about being too lean upstream and downstream.

There were no codes after new O2 sensors, but I switched them back. I tested the new o2 sensors resistance as stated in the Toyota shop manual (it is supposed to read 11-16) and the front one read 16 and the rear read 21 so I think I may have gotten sent a bad rear O2 sensor.

7

I have found buying cheap brand name stuff on Amazon to be a fool’s errand sometimes.

8

Denso is who makes the OEM version of the sensor, edit … at least it is for my Corolla. I don’t expect that you purchased Denso is the problem. Of course it is always possible there’s a sample defect. But the resistance measurements you made are pretty close to spec. I think what you are measuring is the heater coil resistance, so one of them being a little high would mean it might take a few minutes more for the O2 sensors to kick in and for the ECM to go into closed loop. The O2 sensor itself could be bad though.

Did you measure the resistance in the old sensors? If not, do so. I’m thinking one or both of the old sensors were in fact no good, and you’ve been running in open loop. Which is fine, the engine can run fine in open loop, probably wouldn’t even notice anything unless you were coming close to some performance limit or another. But when you switched to the new sensors, that confused the ECM, as it had been compensating for the bad sensor.

What to do ? hmmm … I think if I had this problem I’d disconnect the battery overnight. Put in the new O2 sensors, double check there isn’t any obvious problem like a missing wire or vacuum connection, and try again. It may take some time for the ECM to learn how to operate the engine with the new sensors. A little more patience with the new sensors may be needed. As said above, you shouldn’t note any difference in performance, old vs new, until the sensors warm up to operating temperature, which can take 5-10 minutes. If you do note some difference, post back.

If the car simply won’t run well with the new sensors, it could still be , and indeed likely, that the new sensors are ok. The cause would be that the ECM is now going into closed loop, and there’s something else wrong. You’d diagnose this by starting with the diagnostic trouble codes once the ECM has a chance to adjust to the new sensors and everything has stabilized.

9

Did you double check the part numbers on the new O2 sensors?
It has happened to me that I got the wrong part numbers on a part.

10

Mike in NH

O2 sensors are not something you replace for the heck of it.

Of course not, but for what the military calls high-rel, you will at a certain mileage.

When I asked some time ago, those who understood the issue admitted that sensors start deteriorating at maybe 100,000 or 120,000. So, the first predictable failures will happen in that range.

If you live close to a good parts store or Toyota dealer, and don’t plan any long trips, wait until they fail. If you live a long ways away, as I do, and parts will probably be air freighted in, then for high rel, you would replace them at around 100,000 or so.

I knew this for my 2002 Sienna. So, in September when I went back to the States, I had a plan to replace all of my sensors. Call it for the heck of it if you wish. I prefer to think of it as preventive maintenance.

When I stopped in McAllen for some days, I decided to wait until I went north to our home of 30 years before retirement, to visit a foster daughter and brother for the last time.

Coming back, around 100 miles after starting back, we stopped at a truck stop on the Interstate. My wife wanted a souvenir post card for our last visit to the state.

The minute I restarted the car, the CEL came on. I stopped at the first rest stop to put on the scanner, and found that Bank 1 Sensor 1 had an open heater. This makes sense, because any filament type device does most often open up the instant you turn on the power to it. I kept an eye on it, and performance and mileage was normal, which makes sense since the heater only makes a big difference during warm-up.

When I got back to McAllen, I took the car over to Pharr and had a new one put on. Note that the sensors had somewhat over 100,000 miles on them.

Next year, I expect to have the rest replaced, if you wish, “for the heck of it.” If my highly talented SIL will help me, I might try to buy the Denso from Amazon to save a bundle.

11
When I asked some time ago, those who understood the issue admitted that sensors start deteriorating at maybe 100,000 or 120,000. So, the first predictable failures will happen in that range.

I’ve never had one fail…even on vehicles with over 300 and 400 thousand miles.

12

@MikeInNH‌

I see oxygen sensors fail all the time, on various makes and models

And the vehicles typically only have a fraction of the mileage you mentioned

oxygen sensors are one of the most common automotive failures

13

UPDATE:

Fiance’s dad cleaned out the mass air flow sensor and ran the car a bit more with the old O2 sensors on and the car was running great again, but check engine light came back on with same old codes.

I returned the O2 sensor that had the high resistance reading than spec and got a new one, replaced them. While the car did sputter and misfire a couple times (and way more exhaust than normal) it was nowhere near as bad as before and after 10-15 minutes it had no problems.

14

@db4690‌
You’re the first mechanic who ever said. I’ve talked to several professional mechanics on O2 sensors over the years…and they all say it’s NOT a very common part replacement. Most of the vehicles they service on a regular basis…rarely does an O2 sensor need replacing.

15

I’m not a mechanic, but with older Subarus, you often need to change out an O2 sensor. So maybe some brands need it more frequently?

16

@MikeInNH‌

Don’t know what else to tell you, except that I see oxygen sensors legitimately get replaced all the time

By legitimately, I mean that I personally know they needed to be replaced, because they were faulty

Maybe this will throw some light on the situation . . .

In my experience, one of the most common reasons for oxygen sensor replacement is because the heater circuit failed. That brings up the question . . . does it “need” to be replaced? After all, the sensor is still fluctuating correctly. But it’s not 100% functional anymore. And the check engine light will be on, and if you’re in a car with smog tests, yeah, you’ll “need” to replace it, if you want to honestly pass

Here’s something else . . . with severe oil consumption, or overheating, the sensors sometimes get contaminated. While they’re not “dead” they’re contaminated, and are not giving an accurate reading anymore

Those guys you talked to, here’s what may be going on. I say “may” because I see this happen all the time.

Maybe you needed a sensor replaced, and the mechanic told you that he doesn’t replace sensors often, so that you’d somehow feel better about it. After all if you’ve got a Chevy, and he tells you he replaces several sensors on Chevy every week, you might lose faith in the brand

Another possibility is that memory is somewhat selective, as we all know. It’s possible that if the guy were to think about it systematically, he’d realized that yeah, he actually replaced several sensors, and that it was a fairly common repair

17

I know this is old but im just searching about it online and came across this and the same exact thing is happening to me right now I ordered one off rock auto looked soo similar to mine the upstream bank 1 sensor different numbers on it tho … anyways installed it and the check engine light when off for a few minutes popped right back on and said the same thing it was saying before went on a test drive and the car ran horribly it idled so low and was shaky i knew it had to be the sensor i just put it i took it out put back in the old one and she ran perfect again :. Just bad gas mileage lol… anyways got a new sensor coming straight from toyota in a day or two … just my story on it …