MrImole:
Are you sure this story was never written by anyone?

Piyke:
So I was at my mechanic quite recently and he asked me to help him scan one 2010 Accent which was having an occasional vibration at idle. The Car would also hesitate sometimes when the throttle is called upon.

Well, the car had no CEL and since I had confirmed the CEL bulb wasn't removed, I decided to run livedata to take a look at fuel trims and at least try to rule out fuel supply issues, vacuum leak etc.

Fastfoward. I hook up my scanner, run a manufacturer level scan as expected no codes. I then proceeded to take a look at STFT and LTFT but the car remained in Open loop. I just started the car, so I felt it's still warming up but alas it remained so after 5-10mins. This was odd to me as my Accord would hit closed loop at the blink of an eye after startup.

I then decided we should take it for a spin to help it "heat up" . Holding the scanner while the mechanic drove, it still refused to come out of open loop. We drove maybe almost about a km, but I was on a schedule and had to move on.

Bottom line I didn't read the fuel trims.

This was quite surprising to me, but my plausible explanation is that the car probably does not use heated O2 sensors thus requiring a long warm up time before the the O2 sensors become active and then provide the data for the car to enter closed loop.

Any thoughts?

GAZZUZZ:


kia, hyundai from Korea up to 2010 (what iv noticed) do not come with O2 sensors Just a simulation. Funny thing is they have great fuel economy. Another crapy thing is the check light is very useless, you can unhook a major electrical part and it will not turn on the check light. Strange manufacturer.

GAZZUZZ:


kia, hyundai from Korea up to 2010 (what iv noticed) do not come with O2 sensors Just a simulation. Funny thing is they have great fuel economy. Another crapy thing is the check light is very useless, you can unhook a major electrical part and it will not turn on the check light. Strange manufacturer.

sultaan:
O2 for the car I checked are heated

http://www.rockauto.com/en/catalog/hyundai,2010,elantra,2.0l+l4,1444686,emission,oxygen+(o2)+sensor,5132

I might be one of those skeleton models made for Nigerian market so it might have CEL but you don't know if it has that capability unless you trigger one by disconnecting a cylinder to cause misfire.

Case sounds like a misfire, but if the CEL actually works it is a case of either air or fuel starvation if there is spark.

Start with air first looking for vacuum leaks spray some aerosol(hairspray) around vacuum lines and listen for sound/idle change

If none tell mech to check fuel pressure at injector rail read it at idle and WOT to see if it maintains pressure if theat fails replace filter first(not wash) the fuel pump

I know it is not your car but this diagnosis applies to a lot of users