Misfiring

20

Asked by Jun 11, 2014 at 10:05 PM about the Hyundai Sonata

Question type: Maintenance & Repair

Hi there, I am from Australia and I have a 2005 NF Sonata Elite with a 3.3 v6 engine. For as long as the past 3 years, a check light has been constantly on, stating there is an issue with the 02 sensor. For most of this 3 years, this has not caused any issue and a mechanic once told me, unless your fuel economy gets worse, I wouldnt replace the 02 sensor as it is an expensive job and is probably just a electrical fault. Needless to say, on pulling out of a shop last week onto a highway, i put my foot down to be able to merge properly and my caar lacked power, made loud metalic sounds and the check light flashed. Took it straight to the mechanic, my car is now misfiring on cylinder 1 3 & 5. It is shuddering at all times now and the check light is constantly flashing. I recently had the sparks replaced as per the log book servicing guidlines. I hadnt experienced this misfiring issue before. It is currently down at the mechanic, they found a small air leak in the exhaust system that they claimed could have been the caause of the o2 sensor issue, they said essentially 'suck it and see' and come back as soon as a check light comes back on. To my surprise the check engine light didnt come on within the first km, as is usually the case after having the codes cleared, with i would assume, an 02 sensor code. But my car still had a slight tinny sound and lack of power, especially noticable when the foot was put down and it changed back a gear or 2. Shortly after, the check light was back flashing again and running rought and shuddering. I took it right back to the mechanic and the same misfire codes are coming up. They have had it 2 days now and are replacing the 02 sensor, despite that error code not coming up again on the test drive mentioned. I read a previous post which talked of the timing chain slipping a couple of notches, i also saw a post where someone had Intake Oil Flow Control Valve (24355- 2G000) replaced by a hynudai service dealership and that seemed to fix his issue. I am just a little concerned that the mechanics are replacing things because they just dont know what the problem is hoping it is the cause. The issue with this is that it may not fix the problem, but I still have to pay for it and the price will begin to add up.

5 Answers

74,015

Have your catilac converter checked,may be thats what that o2 sensor was trying to tell you,check your catilac converter may be stopped up.

1 people found this helpful.
74,015

When they stop up you here a rattle.

1 people found this helpful.
20

The mechanic says that the back ones were relatively clean, although some black soot was present, consistent with the engine running rich. They have stated that the front ones are connected to the manifold and therefore would cost thousands to replace. Given that the back ones didnt look too bad, the assumption is that the front ones hopefully wouldnt be too bad either, although i do realise that the front ones would take the bulk of the soot or unburnt fuel but would also expect some flow over into the back ones, which they appear clean... this is my rough theory anyway. I am aware that the cat converters may require replacing, but at such an expense with no guarentee that it will solve the issue, I am inclined to look into cheaper potential issues first. But yes if it comes down to it... I will have it done.

1 people found this helpful.
20

The rattle occurs when I put the car under load, when the check light was flashing constantly, under gentle acceleration, the metallic sound wasnt really present but when i accelerated a bit harder or went up a hill it would. I wouldnt say that it is a rattle, which would imply a loose or broken part, but rather a noise of inefficient, uncoordinated or not in sequence moving parts of the engine.

1 people found this helpful.
74,015

Yes, that metalic sound is raw gas going into your converter,your o2 sensor is telling your ecm it need,s fuel,meanwhile your caty is having to burn up all the raw suit gas,and that is why it,s running this way.Yes it,s expencive but, it will get worse as time go ,s on. Good luck with this.

1 people found this helpful.

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