Okay, skip the sender idea. I'm guessing you have a leaking intake
manifold gasket. Have done a few of these on 4-cyl '06 and newer
Sonatas. This would explain the roughness as well. In fact, it's
usually obvious if you remove the plastic engine cover and look
Yep, that appears to be it. Any idea why this is a common failure mode?
I've never before had a vehicle where the intake manifold gasket
failed and I've run several cars well over 100,000 miles.
Is the replacement gasket better than the original? Do I need to plan
to replace this every 50,000 miles on this engine?
My only suspicion is improper torque from the factory, either too
loose allowing the gasket to get sucked in, or too tight, damaging and
weakening the gasket so it can get sucked in. Usually, a portion of
the gasket indeed gets sucked in. I don't see enough failures to
expect that all cars will have it, just enough to know that with
certain symptoms, this is an excellent first place to look. In my
opinion, the gasket is stout enough-- a couple layers of thick paper
like most intake gaskets. Have seen no difference in construction
between replacement gaskets and the originals.
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