Engine sputter then stop then start?

2014 CHEVROLET SONIC
119,100 MILES • 1.4L • 4 CYL • 2WD • AUTOMATIC
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JONSOLOW13
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I bought this car 3 weeks ago. It was stored for at least 16 months, very low mileage as you can see. Mileage appears legit even though the odometer mileage not showing except briefly when you open the driver door (we think it's lost the connection to the VCM and needs reprogramming) because mileage correlates to the car fax and increases with driving.

After driving about 150 miles, the engine sometimes (irregularly) sputters at a light or stop sign, then stalls. Starts right back up. No engine lights on the cluster.

We thought it might be water in the gas tank, haven't put any Sea Foam in. However, it seems too long for that to be the case.

Any ideas?

Thanks,

Jon
Jan 8, 2024 at 12:58 PM
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JACOBANDNICKOLAS
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Hi Jon, does it ever do this when the engine is cold? If not, it could be a failing crankshaft position sensor. Oftentimes, they will cause a stalling issue when the engine reaches operating temperature. Once the sensor cools a bit, it can start working again.

Do me a favor. Take a look through this link and let me know if it seems to mirror what you are experiencing:

https://www.2carpros.com/articles/crankshaft-angle-sensor-replacement

Let me know your thoughts. Also, let me know if you checked for engine vacuum leaks. That can cause stalling at an idle.

Here is a link that explains how to check:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let me know.

Take care,

Joe

Jan 8, 2024 at 7:08 PM
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JONSOLOW13
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Joe,

It turns out the check engine did come on. There were two codes, but I didn't capture them. In essence, one was an evap leak and the other indicated a potential issue with the MAS. My mechanic friend (amateur, used to be certified) thinks both codes may be connected, and noted a hose near the Mass Airflow hose was loose.

We are going to tighten it, and I'm ordering a new MAS. The "permanent" codes showed an issue with the Cam Position Sensor (or Crankcase Position Sensor). I will re-run a scan and send you pics of the codes.

Thanks so much!

Jon
Jan 9, 2024 at 12:15 PM
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JACOBANDNICKOLAS
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Hi,

Thanks for the update. Let me know what you find. I'm interested in knowing.

Take care,

Joe
Jan 9, 2024 at 8:24 PM
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JONSOLOW13
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So, the actual problem was a bad valve cover and possibly a bad valve cover gasket. Turns out there is a flap in the cover that wore out. We replaced the valve cover (from the junk yard) and gasket (new), and voila- no more problems.

However, we have at least 1 motor mount that is bad, causing engine vibration at idle. Otherwise, the car is great.

Thanks again,

Jon
Jan 22, 2024 at 9:59 PM
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JACOBANDNICKOLAS
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Jon,

Thanks for that information. It's likely it will help others in the future.

Take good care of yourself and feel free to come back anytime in the future. Also, if you need help with the motor mount, go ahead and start a new post and we'll do our best to help.

Joe
Jan 23, 2024 at 7:30 PM