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Discussion Starter #1
Hello,

About a month ago, I overhauled the engine head, and last week I plugged in the exhaust cover, after plugging in I forgot to connect the 2 front and rear oxygen sensors, and drove like that for about 20 minutes. then the engine control lamp turned on and I stop the car and scanned fault codes and immediately realized it was the sensors.
But since then there has been instability in the RPM when I'm stopping vehicle seems to be turning off. I tried to clean the contacts of the sensors in case they became contaminated and then reset the computer, but it didn't get any better.
Plus when I stand outside the car when it is on I smell a strange smell of fuel not really fuel but also not burnt fuel. What could be the problem?

The car is Hyundai i30 2009 auto, 200k.
The engine and chalk oils are full.

The shift of gears feels smooth as usual, and the phenomenon also happens that the vehicle in N and not only in D, in D when I come to a stop is the worst.
I've attached a velocity graph with RPM.

Thanks a lot for your help.
444088
 

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So after finding the codes and reconnecting the O2 sensors have you erased the codes?
I see you said you reset the computer. How?
If you have erased the codes have you taken it for a drive and re scanned?
 

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Discussion Starter #3
So after finding the codes and reconnecting the O2 sensors have you erased the codes?
I see you said you reset the computer. How?
If you have erased the codes have you taken it for a drive and re scanned?
I reseted the codes by the torque app and obd and also I disconnected the negative plug of the battery for couple of minutes.

I'm also took the car for driving and scan after and there is no codes.

But now I scanned again after I saw your answer and there is code p0171- System too lean (bank 1).

What can be the problem? and what can I do about it?
 

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Discussion Starter #7
You are sucking air somewhere.
You mean somewhere that is not through the intake manifold? I mean after the intake manifold or can there also be a hole in the manifolds or before the throttle that can cause it?
 

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Discussion Starter #8 (Edited)
Hi,

3 errors have appeared in torque app in test results, can help pinpoint the problem more accurately?
The results:
MID:$01 TID:$08
Maximum sensor Voltage for test cycle(calculated) - O2 Bank 1 Sensor 1
Max: 1.07946V Min: 0.59634V
Test result value: 0.59463V
FAIL
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MID:$81 TID:$80
- Fuel System Monitor Bank 1
Max: 7.5% Min: -7.5%
Test result value: 9.98%
FAIL
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MID:$81 TID:$82
- Fuel System Monitor Bank 1
Max: 1.2293 Min: 0.76955
Test result value: 1.24928
FAIL

I also attach a graph of some parameters maybe they going help:
 

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Discussion Starter #9
Hey!

I tried and still try to detect the RPM instability problem at a stop (in short: the problem is when the vehicle is not occasionally traveling there is a decrease as if the vehicle is choking and then comes back up. Usually the problem appears more times when the vehicle is in D gear but also appears in N)
And in the meantime, what I have come to realize is that there is no problem with the CO sensors, The MAP sensor is good. The Intake Manifold Stepper Motor idle control valve is ok.

There was some error that suddenly appeared that there was a Misfire in cylinder 2 so the plug was replaced and there has been less black smoke since.
I bought a vacuum gauge and connected it to the PCV hose and measured. I am attaching a video if anyone can direct me to a problem, or any further tests to understand the problem and how to deal with it.

Here: Vaccume test

Thanks
 

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Discussion Starter #12
You have a mechanically sound engine and a clear exhaust. That engine is breathing just fine.
Thank you very much, can you please tell me what could be the reason for the RPM fall in both D and N mode.
I shot the vacuum while the RPM were falling in both D and N.
I also attach a graph of the RPM while shooting the videos.
Drive gear vaccume
Neutral gear vaccume

Thanks again for your help
 

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Your vacuum gauge shows normal. Need to look at scan data to better determine your problem.
 

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Discussion Starter #15
Yesterday I did a test for actuator assy control valve

According to the guides I saw on the internet and there is a difference in the resistance between the 2 pins, in one the resistance is12.0 and in the second 15.6, what are the values that should be? And should there be a difference between them at all?

Thanks
 

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The closing coil should be 14.6-16.2 and the opening coil should be 11.1- 12.7. Workshop manual specs. They control a rotating valve (maybe sticky) which I don't know if you can get access to but should be able to flush it with throttle body cleaner.
 

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Discussion Starter #17
The closing coil should be 14.6-16.2 and the opening coil should be 11.1- 12.7. Workshop manual specs. They control a rotating valve (maybe sticky) which I don't know if you can get access to but should be able to flush it with throttle body cleaner.
Thanks so much.
The sensor seems to be in the thresholds you wrote so that means it is correct. Of course I cleaned it off. It wasn't the most smooth and was very dirty. It didn't get rid of the problem altogether and it seemed less trembling but not yet.
What I noticed today that this only happens after the car reaches a working temperature, you know maybe tell me which of the sensors the computer only refers to after the car heats up to working temperature?

Thanks again for your help
 

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It may well be the crank sensor in it's early days of failing. An easy way to find out is carry a bottle of water with you and when it starts stumbling pour the water onto the sensor. It won't do any damage but cool it down and if the car then runs fine replace the sensor.
 

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Discussion Starter #19
It may well be the crank sensor in it's early days of failing. An easy way to find out is carry a bottle of water with you and when it starts stumbling pour the water onto the sensor. It won't do any damage but cool it down and if the car then runs fine replace the sensor.
Hi, only today I managed to reach the sensor's position and pour water on it, and the vibrations did not stop as I poured water on it.
I thought maybe the problem is the catalytic converter, because I saw that there was a rpm instability in the stop.
And recently the car started to shake as I start driving with weak gas until I step up and then it settles and besides having the smell of fuel from the exhaust which raises my suspicions.
What I noticed was that the O2 sensor after the converter tracks the sensor in front of the converter when in drive. when the vehicle stops, the sensor shows a steady 0.7-0.8.
I also use the torque app and that's where I get it:
MID: $ 21 TIME: $ 80
- Catalyst Monitor Bank 1
Test incomplete or dependent test failed
what do you think?

Thank you very much for your help
 

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Not much goes wrong with a cat and they either are working or not. If they get too hot because of a rich mixture caused by a misfire they can melt or sometimes they just break apart and block the exhaust. If pouring the water on the sensor made it run right I would go ahead and replace it. If it doesn't fix the problem all you have done is spent a few dollars. 07-0.8 is a good reading in my books. The thing is is the O2 sensor output fluctuating?
 
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