2013 ATS 2.5L with 6-speed auto trans, 54k miles, no DTCs.
After the engine reaches operating temp and after a few stops, the engine will intermittently die. The car will start right back up after it dies. Also, at a cold start, there is a brief rattling type noise (like a loose metal shield) and the engine sometimes idles a little rough before smoothing out.
Recent repairs: Throttle position relearn (twice), both VVT actuators (due to DTC), new #3 coil pack (misfire confirmed), new crank position sensor (no DTC, just throwing parts at the symptoms). Also, at 45k miles and about a year ago, the torque converter was replaced under a TSB regarding a known trans / TC shudder issue.
Anyone had an issue with this engine and heavy carbon buildup on the valves? I'm hoping this is not the cause, but it could be. Proper fix is removing the head for a walnut shell blasting to clean the valves and seats.
Anyone found a fuel system cleaner that has proven to clean their valves of carbon buildup? I've read that the Techron additive is among the better ones.
Anyone installed a catch can and noticed a difference (i.e. oil the catch can at each oil change)?
Here are my current thoughts on next steps:
1. Buy a scope or take it to a shop to inspect the valves for carbon buildup
2. Clean the MAF and throttle body with the appropriate cleaners, disconnect battery briefly, then perform a throttle position relearn again
3. Replace cam position sensor even thought the symptoms do not match well and there is no DTC for it.
4. Take it back to the dealer and have them check and test the torque converter solenoid and verify no issues with the trans. Torque converter replacement is still under warranty.
If you've experienced this, please advise what you did to fix it. I'm quite frustrated.