Loss of engine power while idle/Misfires/Service Stabilitrak

[jnb1994]

I've been having some issues with my 2013 2LT R/S (94k miles) for almost a year now and after 4 repairs at the mechanic my family has been going to for 20 years, we still haven't figured out the root problem. I really don't know much about cars so it's been frustrating trying to solve this and seemingly getting nowhere.

The symptoms:
- I can usually tell when I'm about to have problems, it usually starts when I'm idling. RPMs usually stay steady around 500 but then start to bounce around a little more, dropping down to maybe 400-450. That lasts for maybe a minute or so and then starts getting worse.
- The engine will start running really rough, and as soon as that happens my dash starts lighting up, check engine light, traction control light, messages saying "loss of engine power" and "service stabilitrak". When that happens I step on the gas and the car just had no power, I would floor it and would struggle to get up to 30 mph. I'd pull over and usually after turning the car off, waiting a few minutes and starting it back up once, sometimes twice, everything would start running like normal. However, sometimes when I would turn it off the engine would continue running for 5-10 seconds and eventually kind of choke itself off.
- Usually this happens mostly when I'm idling, but there was one time that things did start acting up on the highway. That time when I stepped on the gas I would accelerate enough to keep up with highway speed, but it was noticeably sluggish.
- I've had the following codes at one point or another: P0300, P0301, P0191, one was about running rich or lean but I don't remember what code that was. After the last fix, I started getting P0496 so I'm not sure if that's related or just a coincidence.
- Since I got the P0496 code I have filled up my gas tank twice, and immediately after filling it the car would struggle to start. It was cranking but just didn't sound like it was getting enough gas to get started. Only happened right after fillup.

The repairs:
- Started out with new spark plugs, first time replacing them so it was probably time anyway
- After the spark plugs things seemed normal for a little while, but the issues came back. They said there was excess carbon buildup in the engine and recommended that I take it to another shop to have it walnut blasted. They also recommended that I start using Top Tier fuel, and ACDelco Fuel System Treatment, both of which I have been using since. The shop that did the walnut blasting recommended that I replace the fuel injectors, but I asked my regular mechanic didn't think I had to. It sounded like they were just trying to get a little extra money while they had my engine open.
- After the walnut blasting the engine did seem smoother and things were going well for a couple of months, but again problems came back. This time they said it was the throttle position sensor.
- Again, that worked for a little while, until the problems came back. They replaced the fuel pressure sensor and told me that there was a chance it was the fuel pumps, but they said that would be just under 2 grand so they recommended I try the sensor first.

I've put in over $1500 into this so far and the thought of putting another 2k in and just crossing my fingers that it's actually the fuel pumps isn't sitting well with me. Hoping someone here might have an idea of what's going on or has an idea of something else to look into first, because I'm clueless! Thank you!

[2013ZL1FUN]

You really need to take this vehicle to a shop that has a person that knows how to use a diagnostic scanner and have this vehicle properly diagnosed. Anyone can do a parts cannon on any vehicle and maybe fix it. You are way beyond that point now. If you were in Ohio I could recommend a shop that has a scientific approach to car repair. That is really what is needed at this point because the semi routine maintenance stuff didn't work. Sorry to tell you those shops were just guessing.

[ChibiBlackSheep]

Sounds a lot like issues that i was having with my LFX where the high-pressure fuel pump inside the engine went bad and was leaking fuel into the engine without properly stopping it and pressurizing it.

It causes you to run extremely rich and can foul out plugs quickly.

This was the problem that caused me to drop the money, fix it, and then sell the car.

[xstuntman]

Those misfire codes tell me it could be something as simple as a dirty MAF or bad oxygen sensor but I do agree it needs a professional check up after you knock out the obvious.

[HyperV117]

It could even be a loose spark plug cable. Someone with a good scanner could tell you if it's a specific cylinder thats misfiring or if there are multiple.

[ChibiBlackSheep]

Originally Posted by HyperV117

It could even be a loose spark plug cable. Someone with a good scanner could tell you if it's a specific cylinder thats misfiring or if there are multiple.

the v6 doesn't have spark plug wires. The coil sits directly on the plug