Q: Sporadic RPM surging while stopped in the traffic

asked by on August 10, 2016

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?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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

My car won't shift past 30mph while driving and it revs up.

Hi there. It looks like you've got multiple problems with your 95 Ford Taurus. The transmission issue may be due to a clogged hydraulic line, which is why most certified mechanics will recommend a transmission flush as opposed to just...

Engine light still on after replacing the gas cap

This is a simple fix. Replace the fuel cap. The cap sometimes does not reseal after refueling causing the system to detect a leak. Make sure the cap is sealing after you refuel and make sure the vehicle is turned...

Bank 1 and Bank 2 running lean

If lean faults occur after the manifold was removed and reinstalled, this indicates a vacuum leak which also means that unmetered air is coming into the intake. Either a vacuum line or induction pipe is loose, or the manifold is...

Related articles

B2106 OBD-II Trouble Code: Throttle Position Input Out of Range High
B2106 trouble code means there's a range issue with the throttle position input in a 4WD system, caused by a damaged circuit in the 4WD system.
How to Clean a Throttle Body
A throttle body needs cleaning when the engine idle is rough, the engine stumbles through acceleration, or the Check Engine Light comes on.
How Long Does a Throttle Control Cable Last?
As As you drive through the streets and encounter different speed limits, you rely on the accelerator to speed up when needed. This is done through the use of the throttle control cable, which is also called the accelerator cable....