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Q: When the car is driven and parked, it takes about 2hours to restart it.

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My car is a 2005 Hyundai Santa Fe and normally drives well. Over the past few months, whenever the car is driven and parked, it doesn't start until after 2 or more hours. The fuel pump has been changed but the problem still persists. My mechanic wants to change the engine coolant temperature sensor but he is not sure if it's the problem. He conducted a diagnostic test but said the result showed nothing specific. What could possibly be the cause?

My car has 122000 miles.
My car has a manual transmission.

Hi There, What you are describing sounds like an ignition coil pack that may be failing. Ignition coils are prone to this type of erratic functioning or heat cycling when they are beginning to fail due to the temperature fluctuations under the hood which ultimately cause them to shut down causing the car to only run after cooling down for 30-40 minutes. Ignition coils are coated with a varnish-like insulation that becomes brittle over time after being stretched then contracted repeatedly The insulation develops small fractures that open when heated and close when cooled. When open, they allow shorting of coil windings and decrease or eliminate the coil’s ability to function. This process will repeat itself continuously until the coil ultimately fails completely and must be replaced. Other components that contain heat sensitive materials include parts like coils, injectors, igniters, and some sensors. Any of these may be potentially subject to this same kind of heat cycling problem which can be very difficult to trace. I would recommend having a professional from YourMechanic come to your location to diagnose and inspect your ignition system.

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