Skip the auto shop - Our mechanics make house calls

Q: At light or slowing down, car has irregular idling rev

asked by on

There is an irregular idling rev when I am stopped at a red light or when I slow down. Sometimes the engine will independently go off. The sound of the engine fluctuates from low to high and also to the level of almost going off. I recently had the car serviced by a local MB dealer, but they are not able to find the problem. In your professional expertise, what is causing this and how can I get it corrected?

A: Hello. Most of the time when this issue occ...

Hello. Most of the time when this issue occurs, it is due to a faulty idle air control valve. This valve is responsible for letting some air from the air cleaner bypass the throttle body so that the engine can breathe without the accelerator pedal being depressed.

The idle air control valve also controls the air fuel mixture at idle and if the valve has a fault, this could cause the engine revving to be inconsistent. I would recommend having another mechanic check your idle air control valve for excessive carbon build up or faulty electrical components. If either one of these are found, the idle air control valve should be replaced with a new one. If you would like to have this diagnosed, a certified professional from YourMechanic can come to your car’s location to pinpoint the cause of the rough idle issue.

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

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: my neighbor took car to mechanic, to replace struts, all four, parts and labors around 1300 dollars. reasonable?

The price for parts and labor to replace all 4 strut assemblies and alignment after installation of parts is very reasonable at $1300. When I look up labor the two front struts labor is about 4 hours and the rear...

Q: Changed alternator, battery, starter, remote battery but no crank for a sec and no more, no start thanks

The system should be scanned for faults. A common fault to cause those symptoms is the EIS (Electronic Ignition Switch) failure. It can also be a faulty key. Start by trying another key if available. The remote battery is just...

Q: Power loss, check engine light comes on and off

It seems you have a few things going on. As far as the steering issue goes, this may be fixed by having the vehicles suspension alignment adjusted. Next, have an experienced technician, like one from YourMechanic, scan the vehicle and...

Related articles

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...
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...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...