Rough idle on warm engine?

[12114]

I very recently bought a 2012 rspec with pretty high mileage. I started noticing it idles kinda rough after I pull off the highway and wait at a red light. You also get the feeling the car is about to shut off on you, and the dash indicators like the speedometer are flickering. The shakiness also happens on cold start sometimes. Is it the damn carbon build-up again? Or could be something else?

 

[Qship]

Sounds electrical to me. Check the battery/Battery Terminal to start with. Clean up any corrosion.

 

[12114]

Sounds electrical to me. Check the battery/Battery Terminal to start with. Clean up any corrosion.

Funny story, I was having electrical issues too, bad contact with the battery. Cleaned it the other day, and put some techron in a few weeks before. Hasn't happened since techron. Anyway I have a new issue with oil consumption now. This car is quite a headache unfortunately...

 

[air540g]

Due to high mileage, I suggest you to replace those parts:
1)spark ( every 150,000km)
2) ignition coil ( 150,000-200,000)
3) fuel pump assembly ( 150,000-200,000)
4) clean throttle body
5) clean injections ( use fuel additives)
6) if your car is GDI engine, clean valve carbon.

your car will be smooth.

if your car is over 200,000km, replace crankshaft position sensor.
replace pcv valve and hose.
replace radiator fan motor ( only motor)
replace radiator upper hose.

 

[wmcii]

I have a 2012 4.6L v8. I started having issues where the car would turn over but not start for ~5 seconds when it was a warm start; it had a rough idle on a cold start; and eventually started to randomly stall at stop lights. It ended up being the crankshaft position sensor. It was easy to replace myself and the part was $65 at the Hyundai dealer. I'm not sure this is your problem, but it sounded similar to my experience so I thought I would share.