Q: On a good day car starts very easily in the morning or if rested for about 30 mins. However, it does not start when warm

asked by on November 10, 2016

i have changes MAF sensor and Coolant temperature sensor. car starts easy at mornings and once started can run all day without stalling and cutting out . if u cut the engine while warm and leave it for a few minotes it wont start.Leave it rested for 30 minutes then it will start
My car has an automatic transmission.

Hey there. This is a common sign of a faulty ignition coil. Ignition coils are coated with a varnish-like insulation that becomes brittle over time after being stretched then contracted as the copper beneath them expands and contracts faster than the insulation around them. The insulation develops small fractures that open when heated and close when cooled. When open, they allow shorting of coil windings decreasing the coil’s ability to function. This type of temperature cycling happens because every time you shut the engine off, the fan stops running, the coolant stops flowing and the temperature under the hood rises.

Every time you start the engine again the coolant flows, the fans turn on, and the temperature drops. The areas in and around the tops of the combustion chambers, the exhaust manifold, and the exhaust components are hundreds of degrees hotter than the outside temperature under the hood. When this heat dissipates and is absorbed under the hood, it is trapped causing this cycling effect.

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 problem which can be very difficult to trace. I would recommend having an expert from YourMechanic come to your location to take a look at your truck to properly diagnose the hard start and proceed with the proper repairs.

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