Q: Car turns on and runs fine when cold but when warms up it randomly turns off

asked by on November 30, 2016

Well I took my car to a mechanic and he replaced the crankshaft position sensor and the fuel pump and it seemed like it fixed the problem I drove it around for a little and the car was fine, so I drove the car home and half way to my home the car sputtered and turned off and would not turn back on so I had to push it to the nearest parking lot. This whole problem started when I put a fuel system cleaner, any ideas on what it could be? We check the coils I replaced the spark plugs We tested the fuel injectors I'm confused and all out of money. I really need this car back up and running :(

My car has 143000 miles.
My car has an automatic transmission.

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 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 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. 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 vehicle to properly diagnose your ignition system.

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