I have a 2008 Hyundai Tucson GLS 2.0L I4 with an intermittent crank/no-start issue; 110k miles, bought used a year ago. The previous owner probably bailed on the vehicle because of this issue. New parts: Battery, starter, spark plugs, air filter, oil/oil filter, crankshaft position sensor, timing belt, water pump. 98% of the time, the car starts and runs great. On unlucky days when the 2% comes up, the engine cranks and will not start with repeated attempts. However, after leaving the car alone for a time between 5 minutes and a few hours, it will start up again, sometimes stalling immediately on multiple attempts before returning to normal operation. Several weeks of daily driving usually go by until the next episode.

The car has been towed to the shop many times. It starts right up for the mechanic and he has not been able to replicate the issue while in his care, so he is unable to diagnose the problem. The car used to stall at low speeds and the mechanic did replicate that, identifying a fault in the crankshaft position sensor when it stalled while idling at the shop. That issue has not occurred again but the sensor was just replaced a month ago so who knows, it could happen again. There were times when the engine stalled and would not start up again.

The car has been at the shop for the past two weeks and the mechanic has been gracious enough (or he’s tired of having it reappear at his shop) to keep it and continually test it. So far, no issues. If the car does not act up for him, I’m willing to shoot in the dark a little and replace components that could be the culprit, especially if they are relatively cheap. The mechanic would rather catch the problem in the act but I feel bad for having him invest so much time into this vehicle.

Any ideas on what this could be? Are we talking dozens of possibilities or can this be narrowed down to a few? What can I do to diagnose the problem when it is occurring? Selling this Tucson and buying another vehicle would be a loss of thousands of dollars, so I’d rather not go that route. Plus, the next owner would be stuck with the issue. It’s a great vehicle when it works.