2012 3.8 Genesis has rough idle at start up

[greygenesis]

My 3.8 2012 Genesis rumbles at idle upon a cold start, but has a smooth and silent idle after I drive it a bit.

Is this normal? Why is there a faint thumping when engine just started?

 

[Bill K]

How many miles?
Do you use tier 1 gas?
If not, do you use the Hyundai GDI cleaner?
Under warranty??

 

[greygenesis]

How many miles?
Do you use tier 1 gas?
If not, do you use the Hyundai GDI cleaner?
Under warranty??

40K miles
I use reg unleaded 87 Octane, and no not tier 1
Never heard of GDI cleaner
Yes under factory and powertrain warranty

 

[Bill K]

Since the GDI engine uses direct injection, the tops of the intake valves tend to get dirty.
Hyundai recommends using either tier1 gas, or to use their cleaner.
If you take It in to the dealer they'll probably tell you the same thing and charge you to do it. I would recommend buying a GDI cleaner from the dealer and do it yourself. This way, you can take it in and tell them you already did it.

 

[greygenesis]

Since the GDI engine uses direct injection, the tops of the intake valves tend to get dirty.
Hyundai recommends using either tier1 gas, or to use their cleaner.
If you take It in to the dealer they'll probably tell you the same thing and charge you to do it. I would recommend buying a GDI cleaner from the dealer and do it yourself. This way, you can take it in and tell them you already did it.

Ok thank you for the info.

What is considered tier 1 gas?

How much is the GDI cleaner?

 

[craigt]

Perhaps this: http://www.toptiergas.com/retailers.html

 

[greygenesis]

I filled up Supreme gas at Chevron, and the smoothness, power is significantly better. Idle roughness is way down too. Seems low-quality gas is the culprit. (I had been filling up reg unleaded at Fuel Depot gas station)

 

[Subninja]

This has to do with GDI carbon build up on the intake valves. You should never use 87 octane on GDI engines. Have to take it to get the intake valves media blasted and it will probably run you about $1500.

 

[craigt]

This has to do with GDI carbon build up on the intake valves. You should never use 87 octane on GDI engines.

Citation please?

The manual states 87 is recommended.
Top Tier gas has detergents in 87 to prevent carbon build up.