Hyundai Forums banner

1 - 16 of 16 Posts

·
Registered
Joined
·
8 Posts
Discussion Starter #1
Hi all,

I have been having issues with intermittent stumbling or slight engine hesitation. It started on a long road trip when I was going up a steep hill in single digit temperatures. The engine stumbled, lost a lot of power, engine light was coming on when I hit the accelerator and then eventually stayed on, didn't feel like all cylinders were firing and that went on for a few minutes until I reach my destination. I parked the car for a few hours then went back to take a look, started it up and it started right up, no check engine light, no issues. I then drove it back home (1 hour drive) and it drove without a hitch no issues at all. I took it in to a mechanic the next day and had them look at it and they kept it overnight, ran diagnostics, said there was no codes stored at all, they test drove it a few times and found nothing, I had a minor exhaust leak that they fixed. I then drove it for a week and every once in a while I would feel a slight engine hesitation, so I took it in to the dealer and they ran full diagnostic, test drove it for a few days and they said they can't find a thing wrong with it. So I drove it for a while, ran some Techron through it, put in new ignition coils (had put in an aftermarket set this summer so thought that might be it so replaced with OEM), and still get that slight hesitation every once in a while. Mostly after the car has been warmed up and driven for a while. It always starts right up even on cold mornings and runs smooth when cold. So I decided to get bluedriver which allows me to record sensor readings using my phone from the OBD2. I drove it for an hour and sure enough towards the end of the drive I would get some slight hesitations and noticed that my O2 sensor Bank 1 - Sensor 2 would drop to 0 volts right before a hesitation most of the time. I then recorded some fuel trim data on the drive back. My best guess based on my limited knowledge is that I either have a vacuum leak, a failing fuel injector, or a bad MAF or O2 sensor. I'm attaching the log files from my drive down (at 8:43pm and then my drive back at 1:43am). If anyone has any advice on what might be wrong or how I can better diagnose it or fix it then please let me know.

Any help greatly appreciated!
 

Attachments

·
Registered
Joined
·
3,261 Posts
Look at the engine speed. It may be the crank angle sensor. Also what the tacho doing when it starts cutting out.?
 

·
Registered
Joined
·
8 Posts
Discussion Starter #3
Thanks for the reply, the tacho remains pretty steady when it's hesitating and usually if I accelerate the engine responds and stops hesitating and picks up speed.
 

·
Registered
Joined
·
3,261 Posts
Possible air leak. When you put load (accelerate) on the engine is when it will misfire with plugs,leads coils etc so you can eliminate any of those parts. Only when hot it may be an air leak because the ECU delivers more fuel when cold. If you have a scan tool you could look at the fuel trims at idle then at say 2000rpm which could confirm a leak.
 

·
Registered
Joined
·
8 Posts
Discussion Starter #5
Thanks charlescrown, I did look at fuel trims but unfortunately I don't really know how to interpret the data. The file I attached DataLog-Feb_13_2020_1-43-49-AM.txt shows a log of fuel trim data and O2 sensor readings from a start up until the end of a 45 minute drive. What would I be looking for in the fuel trim data?
 

·
Registered
Joined
·
8 Posts
Discussion Starter #7
It is a csv text file but I had to chance the file extension to text to upload it, if you turn the extension back to .csv you should be able to open it in excel without a problem. Thanks for taking a look.
 

·
Registered
Joined
·
8 Posts
Discussion Starter #8
Quick update, this morning the car misfired and threw a P0304 code. Parked it and then started it up again and it started right back up smooth and engine light was off.
 

·
Registered
Joined
·
8 Posts
Discussion Starter #11
I had replaced all the ignition coils with OEM ones after it misfired the first time and still having issues. Plugs are also fairly new but I'll take a look at those. Gonna try to go back to the mechanic with more data this time and see if he can figure it out, hopefully third time's a charm.
 

·
Registered
Joined
·
8 Posts
Discussion Starter #13
Looks like it might be a bad plug, the plug on cylinder 4 was a bit loose and the electrode strap was gone but it was still working most of the time. Hoping it was a cause rather than a symptom.

Thanks for your help charlescrown and Propflux01
 

·
Registered
Joined
·
823 Posts
When you say strap, are you referring to the ground electrode? Please let us know if this is the fix, or the problem returns.
 

·
Registered
Joined
·
3,261 Posts
When the ground electrode has been burnt off its a classic sign of not tightening the plug like you said. Thank the gods that it didn't destroy you engine.
 
1 - 16 of 16 Posts
Top