Skip the auto shop - Our mechanics make house calls

Q: Warm starting Problems

asked by on

The vehicle will start-up fine when cold it will run alittle rough. I can drive wherever I need to go. When I shut it off and let it sit for 10 minutes and it will start, but idle down, run rough, and stall. Will have to do that multiple times to finally get it to start and stay running. It only does it when its warm and sits.

My car has 105000 miles.
My car has an automatic transmission.

This sounds like a common sign of a failing ignition coil. Components that contain heat sensitive materials include parts like coils, injectors, igniters, and some sensors. 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 manifolds, 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 like ignition coils are very sensitive to heat when they are beginning to fail. Ignition coils are coated with a varnish-like insulation that becomes brittle over time after being stretched then contracted repeated as the copper beneath them expands and contracts at a higher coefficient than the insulation. 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. 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!

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: Fail safe mode

Hi there. When a car runs out of gasoline, it can cause serious damage to the fuel pump and other fuel system components. If you're able to start your car but it quickly dies, it is likely that the fuel...

Q: 2011 Chevy Aveo has no spark at cylinders 2 and 3

The coils on your vehicle are all housed together in a carrier assembly. If two of the four coils aren't producing spark, there's a good chance the carrier is to blame. A professional, such as one from YourMechanic, can repair...

Q: Nonstop backfiring

Backfiring occurs when the air fuel charge in a cylinder(s) fires at the wrong moment often when the exhaust valve is opening. There are backfires into the intake manifold, too, however. If during your work on the engine you moved...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
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...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...