Skip the auto shop - Our mechanics make house calls

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

asked by on

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.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  1. Home
  2. Questions
  3. Car turns on and runs fine when cold but when warms up it randomly turns off

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: I just got a new clutch but after an hour of driving it stopped going into gear and stuck on neutral.

first try to put transmission into gears with engine off to see if the problem is in the shift linkage or it is inside the transmission or it is in the clutch if it only happens when running.

Q: Engine shut off while driving and won't start.

Hi there: The symptoms you're describing above could be one of several different problems; ranging from serious internal engine damage caused by the lack of engine oil for an extended period to simple items such as a malfunctioning crankshaft position...

Q: Trying to get it started after sitting for five years

My previous comment about timing was in reference to starting the firing order with the correct terminal on the distributor cap. If you have the number one plug wire on the incorrect terminal to start the firing order, this is...

Related articles

P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...