How to Fix Stalling and Other Issues After Replacing the Battery

Stephen Fogel
May 2, 2018

stalling after new battery

Replacing your battery is part of every car owner’s life. Every few years, you’ll need a new one. But sometimes fixing one problem can cause another.

Replacing the battery on some vehicles may simply be plug-and-play — just remove the old one, put in the new one, and you’re on your way. But some cars can react differently when you disconnect and then reconnect the primary source of power. You may introduce a serious stalling problem along with your new battery, or at least encounter some electrical issues.

Let’s look at how and why this happens, how to deal with it if it happens to you, and how to prevent this situation from occurring.

Why can a new battery cause stalling?

Over the past several decades, our vehicles have evolved into electronically managed mechanical devices. What were once simple, easy-to-understandters automotive systems are now controlled by sophisticated computers.Â

These computers rely on a consistent power supply for optimal performance. They also require power to retain the correct memory settings that they have “learned” over time. These settings are saved in what is known as volatile random access memory, or VRAM.

But by disconnecting your battery when you replace it with a new one, you cut the flow of power to your vehicle’s computers, if only for a short time. If the power is disconnected for too long, these computers can lose their VRAM settings, including the engine idle settings. Once those are lost, you may experience a stalling problem.

If the memory of the car’s computer is erased, it will revert to default settings. These defaults are ideal for a new vehicle. But over time, your car ages and wears, and crud builds up in certain key places. Your engine computer notices these tiny, gradual changes and compensates for them.

As a driver, you don’t notice these small changes, but they keep your vehicle idling smoothly as the miles pile up. By going back to the default settings, your engine can no longer idle properly. You have a problem.

Get it diagnosed by a professional

Find a shop in your area

Fixing a stalling problem after replacing your battery

Fortunately, your engine’s computer is fully capable of relearning the correct settings. Start by making sure that your vehicle is parked on level ground with the parking brake set. The engine should be cold. All power accessories should be off, including the heat, air conditioning, audio system and interior lights. All the doors should be closed. Here’s what to do:

Step 1: Start the car. If it feels like it’s going to stall, give it some gas to maintain the idle speed. Continue to do this until your vehicle is fully warmed up (watch your temperature gauge).

Step 2A: If it’s idling smoothly on its own, turn on the air conditioning to see if it still idles smoothly. This will tell you if the engine computer is compensating for the additional load from the A/C. Use your foot to maintain the idle speed if necessary.

Step 2B: If it’s not idling smoothly after it warms up, take your vehicle for a 15- to 20-minute drive on the nearest open road. You may have to drive with two feet if you need to brake to slow down and use the gas to keep it idling, so don’t do this in a congested area.

If this doesn’t solve the problem, call your mechanic. You may have a more complex problem than just a computer with amnesia.

Severe cases of stalling after replacing the battery may require that your throttle body or your idle air control valve be cleaned out. Over time, a large amount of carbon can build up inside these parts, pushing them beyond the limit that the computer can adapt to. Cleaning these items returns them to their original condition, and can make a big difference in how your vehicle idles and runs. Ask your mechanic if this makes sense in your situation.

» MORE: Get an estimate for your car repair

How to avoid losing your memory settings

Even if your car doesn’t stall after a battery replacement, it may lose other settings. But there’s a simple way to prevent all of these problems. A “memory saver” device, when used correctly, will retain the computer memory, clock, radio presets, power seat position and many other settings.

This device provides enough power to your system to maintain its settings when the battery is removed. Memory savers can either connect through your dashboard cigarette lighter or power port, or connect through your OBD-II diagnostic port under the dash.

The power sources used can vary, too. Some use a simple 9-volt battery to energize your system, some use their own rechargeable batteries, some use the battery of a second vehicle to provide power, and some use a wall outlet adapter.

Which type of memory saver should you use?

The first thing to check is whether your dashboard cigarette lighter or power port has power when your vehicle is turned off. If it does, you can use a memory saver with a lighter plug adaptor. If it does not, you must use the kind that connects to your OBD-II diagnostic port.

Whichever type you use, read and follow all instructions, and always use the manufacturer’s recommended replacement battery type and voltage.

How to use a memory saver

Step 1: Turn off your vehicle.

Step 2: Connect the battery saver, following the instructions carefully.

Step 3: Disconnect the old vehicle battery and remove it.

Step 4: Insert the new vehicle battery, use a battery brush to clean the cable ends and battery posts, connect and tighten the cables, and make sure the battery is secured in place.

Step 5: Disconnect the memory saver immediately, before starting the car. You are done.

During this process, don’t turn anything on or attempt to operate any power device such as a power window. Doing so will blow the fuse in the memory saver, and you’ll have to start over.

Once you’re done, your car should run and idle just like it used to — maybe even better, if your battery was in poor shape.

Safety tip: There is no other use for a memory saver

The memory saver should only be used for saving settings when replacing the battery, and nothing else. Supplying power to your vehicle when it’s otherwise shut off could result in serious damage to the car and potential injury to you, especially if you’re tinkering around at the time. You don’t want your airbags suddenly going off without warning.

Stephen Fogel

About the Author

Stephen has been an automotive enthusiast since childhood, owning some of his vehicles for as long as 40 years, and has raced open-wheel formula cars. He follows and writes about the global automotive industry, with an eye on the latest vehicle technologies.