2006 Sonata 2.4L Strange Rough Running
My 2006 4cyl 2.4L Sonata has developed a
very strange fault. It idles fine, around town
it's fine, cold or hot & it still has plenty of
BUT, when cruising along the freeway once
fully warmed up it begins sporadically
running rough. If I floor it it gets better. If I
slow down it gets better.
I've checked the coils & there's no sign of
flash over or corrosion on the connectors. I
did replace the plugs, they were old &
needed to be replaced soon anyway & that
improved the matter, but it's still there.
My obd2 code reader shows nothing.
I'm really confused, everything points to a
fault coil pack but which one & why does it
get better when I accelerate when, in theiry,
it should get much worse?
I'm stumped, all help will be greatly
Update. Today I tried seeing if it was engine speed related. At 60mph I shifted from Automatic into Neutral so I could shift down to 3rd. BUT. The moment I shifted to Manual gear change the problem went away & came back if I shifted to Automatic again. Is this a mis-shift & not a mis-fire? Still no trouble codes though.
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