Hi,

I hope you can help me. Two weeks ago our Sonata started to get crazy. We drove about 50 km without any problem. At our destination, when parking, suddenly idle RPM went to 2000. I switched the engine off and tried to start again. And ... nothing... it just kept cranking. And you could smell gas. As we had some minor welding on the exhaust the week before, I suspected the O2 sensor. Either because the crack of the pipe has been closed and now the ECU is getting confused because of probable stored longtime values - or the sensor has been damaged.
I then disconnected the battery for a few minutes to clear ECU etc. (I knew that from Opel/Gm but I have no idea if that helps with a Hyundai too). And then it started again. For the next 2 weeks and 150 km everything was fine.

Today it all began again. It first started very hard, then after a few km it wouldn't start at all. Again disconnected the battery and it worked again.
I had a look at the sensor and bingo: one wire is off. I found out that it ought to be the sensor heating (pin 3 sensor side).
Now what I don't get: could this be it? I find it a bit confusing that the heating has any influence on air/fuel mixture, at least not in the long run. If the cable of the sensor itself would have been off, I could understand it. Has anybody an idea if this could be the reason?

Ok, the flex-pipe is still cracked, but it was since a couple of months, so I don't think this has a major influence on this sudden problem. Anyway it has to be changed, that's for sure, as well as the sensor. Bun I'm still a bit unsure if this solves the problem.

Thanks for any answer in advance!

Greetings from Austria.