Can Bad Spark Plugs Cause Limp Mode?

Most of us have no idea regarding the limp mode. Let us get a clear idea about it. When you are driving like any other normal day, and suddenly you notice flashes in your dashboard. The car drives and works properly but it does not have any power. Now, you must wonder what is wrong with the car? Probably, your car has slipped into limp mode.

Can Bad Plugs cause Limp Mode?

Bad spark plugs alone are unlikely to be the sole cause of a vehicle entering limp mode – however, the bad spark plugs can be a contributing factor in a more complex chain of mechanical issues.

Attributing limp mode directly to faulty spark plugs is an oversimplification: Limp mode is a safety feature activated by the vehicle’s Engine Control Unit (ECU) or Transmission Control Unit (TCU) when it detects serious issues that could potentially harm the engine or transmission.

These issues often involve more critical components like the transmission system, fuel injectors, or significant sensor malfunctions.

That said, if engine misfires caused by bad spark plugs are severe and consistent enough, they could contribute to a chain of events that may eventually trigger limp mode.

Example of how Bad Spark Plugs lead to Limp Mode

For example, persistent misfires can lead to unburned fuel entering the exhaust system, which could then damage the catalytic converter. A damaged catalytic converter could, in turn, cause the ECU to activate limp mode to prevent further damage to the vehicle’s powertrain.

Also, the intermittent knocks which occur while speeding on a highway will not let your car slip in limp mode.

Almost all kinds of engines at particular times, but in mild cases, the ECU pulls down the ignition timing and waits for a little till things get back to normal.

Bad plugs can also cause difficult starts which are often due to failing transmissions and clutch. A failed clutch will put your car into limp mode too. Bad solenoids or improperly adjusted linkage in the transmissions can put the vehicle to limp mode to restrict any further damage.

What is a limp mode?

The limp mode also referred to as limp home mode is a conventional map or calibration used by ECU (Engine Control Unit) or TCU (Transmission Control Unit) when a probable dangerous fault is identified in any of the powertrain units.

This is a self-preservation function that is pre-installed in many vehicles. In simple words, this function identifies any unusual reading from the sensors or irregular mechanical operations and automatically turns it on.

The limp mode of the car acts as the safe option for your car which protects it from any engine damage. This mode prevents your car from completely shutting down and leaving you unprepared in the middle of the road.

This feature lets you limp home safely and comfortably, or it allows you to drive to the mechanic for repair or diagnosis. When any car is working on limp mode, it does several things that work to bring the car’s performance to a smooth and safe drive.

In the limp mode, most car engines try to run rich, as a high air-fuel ratio is often safer than the low air-fuel ratio. Moreover, in limp mode, an ECU will restrict the engine speed or rotations per minute of the engine, delay the time for each cylinder sparks or limit the pull ignition timing, and change the timing of the intake or exhaust valves.

If the car is turbocharged, the map is likely to run with the wastegate fully open, which will restrict the boost pressure to its bare mechanical minimum. That pressure is a magnitude lower than the maximum potential boost pressure that the car normally has.

What are plugs or spark plugs?

Spark plugs are small but essential units of your car. The spark of the electric current is emitted by the plugin through a small gap that launches the ignition. This ignition is essential for the combustion to start the car. They help to put the engine’s pistons in motion and power up your car. Additionally, they can help the car to stay powered up and produce a smooth burn of the compressed air-fuel mixture. They can bear extreme pressure and heat within the cylinder.

What happens when spark plugs turn bad or fail?

For premium performance, the engine spark plugs must be clean and must not have any damage to the electrodes. If the plugs turn bad or dirty, it can affect the performance of your engine. A bad plug is covered in carbon, fuel, or oil. A plug can also turn bad if it is blistered when running too hot. There are several issues if the plug turns foul or bad. Some of them are listed below.

Symptoms of bad spark plugs

  • Lack of acceleration
  • Difficult starts
  • Reduced mileage
  • Rough idling
  • Engine misfires

How to handle the limp mode?

Bypassing the limp mode is not recommended if it is not necessary. The limp mode is triggered only when there might be potential consequences.

You can cause damage to the engine if you turn off the limp mode manually. However, we have listed some tips which can return the car to normal mode from limp mode. However, you should go to the nearest mechanic and get your car checked.

  • Try restarting the car: Sometimes turning the car off and then again on can return the car from limp mode to normal mode.
  • Disconnect the battery: Many cars forget to get their engine light checked. If it has a fault, you need to disconnect and reconnect the battery. You just need to disconnect the negative terminal of the battery and connect it again.
  • Get an OBD/OBD2 scanner: An OBD/OBD2 scanner reads the codes and detects the fault. This scanner helps to identify the particular area where there is a fault and helps the owner or the mechanic to solve the faults. However, before changing the part, you must make sure that there is no bad wiring involved. If the wiring is faulty or broken, then there is a chance that the reading is incorrect. You need to check the conductivity of the wires with the help of a multimeter. This will allow you to identify if the machine is faulty or the wires.
  • Top with some fluids: While having a limp mode in the car, you should check the fluids in the car. If your car is low on fluids, you need to top up with some fluids as soon as possible to get your car back to normal condition.

Final words

Finding the reason why your car has slipped to limp mode can be very time-consuming. If you avoid it for a long time or change the computer settings to rectify it, the result can be fatal and cost you a huge amount of money for repair. So, whenever your vehicle slips into limp mode, you should treat it as a serious issue and take it to the nearest mechanical shop. We have tried to clear all your doubts regarding the issue. If you still have further queries or doubts, write in the comments section below.