Q: Sporadic RPM surging while stopped in the traffic

asked by on

While I'm driving and am about to bring the car to a halt in the traffic, the RPM suddenly increases. When I stop, the RPM drops and then surges again. In other situations, the car idles at 700 RPM. This occurs sporadically. It doesn't matter if the engine is warmed up or cold. The dash isn't showing any lights on. I went to the dealership, and they had the wiring harness to the throttle replaced. The issue is still happening intermittently. The car has gone around 80,000 miles. Do you have any idea what might be wrong?

Fault codes should be read out of the ECM on your 2006 Mercury Montego. All connectors on the engine harness and at the ECU need to be checked for condensation and/or water ingress as these will cause drivability problems. I looked for relevant TSBs (technical service bulletins) and there are none published which cover the drivability concerns you have described. Being able to replicate the complaint while a scan tool is hooked up to look at sensor input settings will be imperative to solving this issue. If you’d like to have this checked, consider YourMechanic, a s certified technician will be able to come to your home or office to diagnose your rough idling issue and make the necessary repairs.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1,000 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. Sporadic RPM surging while stopped in the traffic

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: Should the lights on the Rev counter be red when car is running?

The engine is designed to not go over a certain amount of RPM or engine damage can result. If you look in any vehicle that has an RPM gauge, it will have what is called a red line that the...

Q: I have a leak in the rear brake, brake warning light is on, can I still drive to shop 3 miles away?

Hi there: Anytime you have a brake fluid leak, or any problems with the brakes not working correctly, it's unsafe to drive. It would be best to have your vehicle towed to the shop or have a mobile mechanic come...

Q: My Camry is starting at 2000 rpm's.

Sounds like there is a vacuum leak that is causing the engine to rev up high. If there is no vacuum leak, then the Idle Air Control Valve could be stuck causing the engine idle to fluctuate on startup. I...

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...
How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...