O2 sensor

Tiny
DANIYALKZA
  • MEMBER
  • 2008 HYUNDAI TIBURON
  • 2.7L
  • V6
  • 2WD
  • MANUAL
  • 75,000 MILES
Hi. i have some problems with my upstream o2 sensors for both banks. with torque app i have checked them and both of them stay at 900 m for about 2 seconds and then stuck at 100mv. i have replaced them with OEM ones and seems the problem solved but today after some sluggish acceleration. i have checked them again and again stuck at rich and lean voltage happened.what can cause this?
this is what I'm talking about:

https://vimeo.com/334654561

i recorded this before replacing o2 sensors but now it happens again with new ones. it doesn't happen all the time because i have checked them for about a week and they are cycling pretty good.
One last thing; i have never any codes for my o2 sensors.
now I'm dealing with sluggish acceleration and it comes and goes rapidly.
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Friday, November 8th, 2019 AT 1:54 PM

57 Replies

Tiny
ASEMASTER6371
  • EXPERT
Good evening,

I doubt the issue is the sensors. They are just telling you rich and lean. That fuel mapping is controlled by the ECM.

You should check some thing first.

1. Fuel pressure, Make sure you have correct fuel pressure. Low pressure will cause that reading.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

2. Verify exhaust back pressure. Check the pressure to be sure you do not have a blocked cat converter.

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

3. Engine timing. I would check the timing belt to be sure it is not slacked.

https://www.2carpros.com/articles/how-a-timing-belt-works

Roy
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Friday, November 8th, 2019 AT 4:40 PM
Tiny
DANIYALKZA
  • MEMBER
Thank you for your response.
I don't have catalytic converter and also don't have any codes storied in ECU.
I have checked fuel pressure before change o2 sensors and it was fine.
Last thing is timing. I think if it was timing it could be permanent not temporary problem because I can acceleration good but a minute later it goes bad again and it repeats.
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Friday, November 8th, 2019 AT 5:09 PM
Tiny
ASEMASTER6371
  • EXPERT
What was the fuel pressure?

If you do not have cats, then the light should be on unless you have some kind of bypass.

Roy
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Friday, November 8th, 2019 AT 5:17 PM
Tiny
DANIYALKZA
  • MEMBER
It was about 50 psi.
I'm using o2 sensor spacer for downstream and there is no problem with that and no check engine light or pending code.
I'm troubling with sluggish acceleration now and its intermittent for example when stop at lights then try to accelerate its good but a while after it goes sluggish like its regain its power and lose it.
I have checked everything but find nothing also replace MAF sensor with new OEM one.
Update:
Today I test it first it goes to close loop very soon I mean when coolant temperature was about 40 degrees.
Second I have unplugged both upstream sensors and car accelerate so much better, but I can't believe if my new o2 sensors is defective as well as my previous o2 sensors.
I should mention one more time that there is no check engine light or even pending code in my ECU.
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Saturday, November 9th, 2019 AT 3:37 AM
Tiny
ASEMASTER6371
  • EXPERT
Okay, the down-streams have no effect on the running anyway.

Do the other 2 checks I suggested and let me know.

Roy
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Saturday, November 9th, 2019 AT 4:48 AM
Tiny
DANIYALKZA
  • MEMBER
Thank you.
You said 3 things include fuel pressure, catalytic converter and timing.
About fuel pressure as I said it was about 50 psi. For catalytic converter I don't have catalytic converter on my car because I removed it. I did timing about 30k kilometers ago and didn't have any problem since.

As I mentioned, today I unplugged my both upstream o2 and see lots of difference in acceleration, but I don't know what's wrong because they are new and also OEM.
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Saturday, November 9th, 2019 AT 6:24 AM
Tiny
ASEMASTER6371
  • EXPERT
When you did that, the ECM went to a default mode or open loop. That is why it ran better.

Like I said in the beginning, the sensors are not the issue.

You have a control issue.

Do you have a scan tool that can read live data on all the sensors?

Roy
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Saturday, November 9th, 2019 AT 6:28 AM
Tiny
DANIYALKZA
  • MEMBER
I have torque app on my phone and except crankshaft and camshaft sensor I have checked almost all sensors in my car and they are all in good shape I think, but I can record a video from my sensors data if you want.
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Saturday, November 9th, 2019 AT 7:09 AM
Tiny
ASEMASTER6371
  • EXPERT
What are the long term trims on the upstream O2 sensors?

Roy
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Saturday, November 9th, 2019 AT 7:14 AM
Tiny
DANIYALKZA
  • MEMBER
I have reset my ECU yesterday but before that it was at 0.
Sometime I see that it goes to -0.8 and -1.6 (i mean 0.8% rich and 1.6% rich) but never stuck for long time on each one and fluctuates between this 3 percentages.
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Saturday, November 9th, 2019 AT 7:36 AM
Tiny
ASEMASTER6371
  • EXPERT
You do not have a vacuum leak.

I would not dismiss the timing belt either. I would still verify.

Roy
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Saturday, November 9th, 2019 AT 7:45 AM
Tiny
DANIYALKZA
  • MEMBER
I think if it timing problem it would be permanent problem, but I haven't any noise or idle problem and still I think unplug o2 sensor can't affect timing problem.
What else could be the problem?
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Saturday, November 9th, 2019 AT 10:32 AM
Tiny
ASEMASTER6371
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Again, I would not assume anything. It still needs to be verified.

Injectors could also be an issue but that should have shown up on the long term trims.

Roy
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Sunday, November 10th, 2019 AT 4:45 AM
Tiny
DANIYALKZA
  • MEMBER
Then you think it is timing problem?
I have a p0335 code once that occur with a hiccup but after that it never shows again. I have checked crankshaft position sensor after that but it didn't seems bad at all.
This problem makes me crazy for longer than one year.
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Sunday, November 10th, 2019 AT 4:57 AM
Tiny
ASEMASTER6371
  • EXPERT
Seem bad? How did you check it?

Possibilities below.

Roy
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Sunday, November 10th, 2019 AT 5:05 AM
Tiny
DANIYALKZA
  • MEMBER
It doesn't seem fried or damaged or anything else and its fault code didn't show up again.
I have checked everything I can find in the engine including:
TPS
MAF
Intake air temperature sensor
Coolant temperature sensor
Injectors
Ignition coils
Spark plugs and wires
Fuel pump and filters
But nothing. I mean there was no codes. Checked their resistance with dvm or their values and live dates on torque app.
The only thing that didn't work normally was o2 sensors that I changed them.
But one strange thing is my long fuel trim is the same as before o2 sensors change for both banks even after o2 sensors changed and reset ECU.
Just one thing changed in car behave
with my previous o2 sensors when I started engine from cold start sluggish acceleration was permanent unless I restart engine after restart engine, that sluggish acceleration was gone completely.
But now it's comes and goes even after restarting engine.
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Sunday, November 10th, 2019 AT 5:33 AM
Tiny
ASEMASTER6371
  • EXPERT
Again, the O2 sensors just send a signal to the ECM for fuel mapping.

They were never the problem. They did there job.

Visual checks of the sensor are not checks. Its actions are what needs to be checked. One of the checks is alignment of the cam and crank pointing directly at the timing belt.

Roy
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Sunday, November 10th, 2019 AT 5:38 AM
Tiny
DANIYALKZA
  • MEMBER
So the timing checked everything was aligned and right. Now what do you think?
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Sunday, November 10th, 2019 AT 4:03 PM
Tiny
ASEMASTER6371
  • EXPERT
Was the belt loose? Was the tensioner tight?

Roy
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Sunday, November 10th, 2019 AT 4:07 PM
Tiny
DANIYALKZA
  • MEMBER
No the mechanic, checked the belt and tell me nothing is wrong about timing or belt.
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Sunday, November 10th, 2019 AT 5:09 PM

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