The vehicle in question is a 2012 Chevy Cruze LT 1.4L w/ Manual Transmission 111,000 miles
I've notice the last 1000-2000 miles, the car would have a inconsistent rough/jerky idle.
The rough idle is now more consistent but only when the vehicle is at operating temperature.
It's kind of like the rough idle you get with the AC on, but in this case, the AC is off. If I turn the AC on the rough idle gets worse.
The car will not stall and there are no engine codes present or stored.
- The car still drives perfect and smooths out at any rpm over 1000.
- Valve cover/Intake manifold/Throttle Body/Fuel injectors were replaced under warranty around 75k so they are still relatively new.
- New O2 sensors installed at 90k; I monitored the O2 sensors on OBD Fusion (Iphone App); they are getting proper voltage.
- New spark plugs went in at 50k and 100k with .28 gap
- The entire cooling system was replaced at 95k-100k
- New coil pack installed 100k. I pulled the coil at 111k and made sure the springs were straight.
- I suspected it was the valve cover going bad again so I changed it; it wasn't the valve cover. Engine still looks new with 0 carbon build up on the inside.
- Plastic pipe between air box and turbo was loose, but made no difference once tightened.
- Cleaned both MAF sensor and K&N air filter.
- Always use premium from Shell/Costco with fuel treatment every 5000 miles.
- The vehicle has no oil/coolant leaks at this time.
- Haven't checked spark plugs/spark plug gap; my spark plug socket has been misplaced in a move.
Anyone have an idea of what the problem is?
Gonna have to go for a GM diagnostic if I can't figure it out soon.