Q: engine idles rough and slow after replacing the battery

asked by on

After replacing the battery, the engine idles very rough and will die with the air on.

My car has 225000 miles.
My car has an automatic transmission.

You will need to re-learn the idle for the vehicle to get it to idle high enough. You should first clean the throttle plates and throttle body and idle control valve. When you disconnected the battery, the idle control was reset to factory and will idle differently unless you relearn the idle again.

After cleaning the parts out, then start and run the engine at 1500 rpms to warn engine for a few minutes, and then let the car idle with all accessories off for two minutes. Put the vehicle in drive and let it idle for two minutes then turn on A/C on medium blower speed, and then let it idle in gear for two minutes. Put it back in park and idle for two minutes with the A/C on. Then road test for about 5 miles in stop-and-go traffic. This should fix the idling issues.

If you need help with all of this, consider having a certified technician from YourMechanic come to your car’s location to diagnose the rough idle and perform any needed tasks to have this resolved.

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
  1. Home
  2. Questions
  3. engine idles rough and slow after replacing the battery

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 truck is shaking.

Hello There, It sounds like you may have a faulty fuel pump that may have been damaged as a result of running it out of fuel. As you may know, today's fuel pumps require the fuel to keep them cool...

Q: Q: The car makes noises while making a turn to the left

Depends on where the noise is coming from on your Mercedes C320. If it is from the front end, then it is likely a worn suspension component such as a sway bar link or a steering component like a tie...

Q: have to push on main fuse box to get the engine to start and idol

You need to first check all the fuses, the connections at the battery cables, and the connection at the cable to the fuse box. My guess is that there is likely a loose connection at the fuse box or at...

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 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...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.