Skip the auto shop - Our mechanics make house calls

Q: Check engine light flashing at hwy speed

asked by on

Start vehicle and has slightly rough idle with check engine light staying on, only in idle position Get moving at highway speed and light starts flashing Also sometimes hard to start, have to slightly press throttle to start

My car has 156000 miles.
My car has an automatic transmission.

A: Have a certified technician start off by sc...

Have a certified technician start off by scanning the system for fault codes. When the check engine light is on faults will be stored in the system. These faults will give the technician a direction to take do diagnose the fault. Something like a misfire can have the check engine light on in a solid state when at idle, but flash at speed because the fault is seen more often. This can also lend to a hard start if all cylinders are not firing properly.Misfiring can be caused by ignition components such as bad spark plugs or a bad ignition coil. Misfires can also be caused by improperly firing fuel injectors, either because they are clogged or failed.

Have a certified technician check for misfires and isolate why the check engine light is on and flashing.

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: Air bag light staying on and now the car won't start.

There has seen many same complaints of the air bag light on these vehicles and may be a manufacturer problem at this point. I would not recommend any one attempt a repair unless they are qualified to do so. The...

Q: Truck will not go forward. I have replaced the water pump and radiator. It had been like slipping gears for about week and is leaking oil.

Hi there. Check all of the fluids in the vehicle and see what is low. If the transmission fluid is low, top off the fluid and see if the transmission stops slipping. If the transmission continues to slip, then there...

Q: "Service Stabilitrak" has come up on my dash and I do not know what it means?

Hey there. These messages are there to tell you that the main computer has detected an issue with the systems. The warning lights are very general. They can mean the system is malfunctioning, the system has been turned off, or...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
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 Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.