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I have a 2011 Kia Forte SX with dual(-ish) transmission (shifting paddles on the wheel, and a slot by the shifter to move up or down gears). It currently has 62k miles on it, and was taken to a Jiffy Lube in November 2016 for routine maintenance.

The first time it had lurched was after accelerating from a complete stop. I went to accelerate in a typical manner, and it had lurched forward twice; the second time about half a second after the first. I had been driving for about 10 minutes at that point, the road was flat, weather was nice, no change in driving habits or route.

The second time I was moving at about 30MPH up a slight incline (freeway on-ramp) accelerating to the posted speed (60PMH) when I experienced the same behavior. It was a little bit wet at that point, but no change in my driving behavior.

The third time I was moving at about 40MPH up a steeper incline (going up a hill) and it lurched again.

It lurched twice each time, about half a second after the first lurch.

My car has an Eco boost mode on it, and is always on unless I've started shifting manually. Each time this has happened, the Eco mode would not turn on again. Typically, if I began shifting manually, after about a minute of no shifting being done, it would switch back to proper automatic, and Eco mode would be turned back on.

Some other symptoms I noticed were:

  • If it happened once during a drive, it would happen more often during that drive.
  • After it happened, the gas pedal was ineffective (pushing in the gas pedal did not result in acceleration, or an increase in RPM).
  • Immediately after it lurches, the Eco light turns off, the check engine light then turns on and back off.

Restarting the car seems to solve it for a time.

I checked the oil shortly after the second incident and noticed that the oil was low. I haven't put in more yet, because I haven't had it say low so soon after an oil change (I got it changed at 61k, expecting another at 66k). I haven't noticed any oil leaks in the parking spots that I've left since then.

Any thoughts on what could be causing this behavior?

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  • Are you saying that this started after taking it to Jiffy Lube? In other words, it did not happen before you took there?
    – CharlieRB
    May 17, 2017 at 17:53
  • Correct, it did not happen before i went to Jiffy Lube, but it has been nearly 6 months since then, and it only just happened this weekend.
    – user28715
    May 17, 2017 at 19:30
  • Adding the 6 month old information about taking it to Jiffy Lube only confuses the question. It obviously has nothing to do with the problem you are having.
    – CharlieRB
    May 18, 2017 at 11:34

1 Answer 1

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The fault ended up being a bad crankshaft position sensor. It's been a few months now, and ever since I got it replaced, I've had not issues.

The error code that was being reported was P0336.

The crankshaft position sensor records the rotation speed of the crankshaft, monitors the engine valves to ensure the pistons can operate properly, and monitors how well the engine is functioning. The ECM uses the information that has been recorded by the crankshaft to make any necessary adjustments to the fuel injection process and ignition timing. When the crankshaft position sensor and ECM are working properly together, they control the vehicle’s emission performance and power output. This mechanism allows the vehicle to be reliable with great driveability.

The crankshaft position sensor has two parts: a rotating disc (reluctor) and the stationary sensor. The majority of crankshaft position sensors have a voltage wire sensor, a ground wire, and a signal wire. These three wire sensors work together to provide the ECM with a revolutions per minute (RPM) signal.

With this information, as well as the information it receives from the camshaft position sensor, the ECM can determine how to adjust the timing of the ignition and fuel injection. When the ECM stops receiving the proper signal from the crankshaft position sensor, and is thereby unable to determine how to make necessary adjustments, it will store the P0336 trouble code.

Related OBD-II Trouble Codes:

  • P0335 OBD-II Trouble Code: [Crankshaft Position Sensor A Circuit Malfunction]
  • P0337 OBD-II Trouble Code: [Crankshaft Position Sensor A Circuit Low Input]
  • P0338 OBD-II Trouble Code: [Crankshaft Position Sensor A Circuit High Input]
  • P0339 OBD-II Trouble Code: [Crankshaft Position Sensor A Circuit Intermittent]
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