These are the causes of misfires at idle and at low RPM

What causes misfire at idle and low rpm? The answer to this question can vary based on a wide range of factors, including the overall state of the engine.

Whatever the circumstances, taking care of your car properly is essential to a smooth-running vehicle. Because car problems can occur at any time, you need to pay close attention to your engine and any unexpected sounds that you notice.

This is especially true if your engine begins to misfire. More importantly, you need to understand the difference between engine misfires at idle and those that occur at low rpm.

Keeping these things in mind, here’s some information that can help you to take the appropriate actions if your engine misfires at idle or low rpm.

Engine Misfire Problems at Low RPM

When you do your research, you may find that engine misfires at low rpm are usually caused by at least one of the following issues.

1. No Spark

If your car does not have a spark, the engine will not fire. This can be caused by several different related problems, including a bad spark plug, a distributor cap that is loose or bad, or wiring that is worn out or bad. In either case, all of these issues can lead to misfires that are related directly to no spark.

2. Lean Fuel

Another issue of concern that can lead to engine misfires at low rpm is lean fuel. These types of problems usually occur when the fuel filter in your car is dirty.

Or, you may find that you have a clogged fuel line or a bad fuel pump installed. Simply put, whenever the air-to-fuel ratio has less fuel than is needed, the engine may start to misfire.

You may also see the codes P0171 – P0172 (i.e. lean or rich fuel mixture) on your dashboard. These codes can help your mechanic determine what type of repairs need to be done.

3. Loss of Compression

The car engine will also start to backfire when the compression is lost. Normally, these issues will arise when your vehicle has a blown gasket, bad valve, or seals that leak. Compression problems can lead to engine misfires because the air and gas mixture will fail to ignite

Each of these issues and other related problems can lead to misfires that need to be repaired.

Engine Misfire Problems at Idle

If your engine is backfiring when you are idling your car, the problem may be caused by dirty fuel injectors. Because the role of the fuel injector is to dispense metered amounts of gas into the engine of the vehicle, malfunctions can occur.

This is especially the case if the fuel injector nozzles are clogged with dirt. Unfortunately, whenever this happens, adequate amounts of gas are not dispersed properly.

Furthermore, if you keep driving the car in this condition, the low fuel levels will eventually cause the engine to backfire or completely stall or die out completely.

Therefore, you must seek help from a professional car repairman that can provide you with the professional service that you need.

How Much do Misfires at Low RPM Cost to Fix?

The answer to this question will vary depending on the problems that have been identified. Since low rpm engine misfires may be caused by one of several problems, the average cost of the different repairs is as follows:

Bad spark plugs replacements. The average cost is between $40 to $350 based on the make and model of the vehicle.

Lean Fuel repairs

The average cost of repairing a car that has lean codes like P0171 can range from $100 to $1,700, based on the severity of the problem identified. Here are some estimates that are linked to the following repair jobs.

Loss of Compression

The average cost of loss of compression repairs can range from $1,000 to $8,000, depending on the severity of the problem identified.

Broken cylinder repairs are estimated about $8,000
Head gasket repairs are estimated about $1,000 to $2,000
Piston rings repairs are estimated about $2,000 to $3,500

These costs can also vary depending on the location of the repair shop and the severity of the problem. So, you can check out at your local authorized repair shop, or online here to get a rough idea of the price that you may be required to pay in your city.

How much does Misfires at Idle Cost?

As reference above, one of the primary reasons for a vehicle to misfire at idle is dirty fuel injectors. To repair this type of problem, your mechanic may recommend one of the following options.

Fuel injectors cleaning. The average cost is estimated at $50 to $80, depending on the make and model of your vehicle. This is a quick fix that may solve your issues right away.

Fuel injector replacement. The average cost ranges from $350 to $850 or more. The cost you pay will vary depending on several different factors, including the number of miles your vehicle has been driven between the last fuel injector replacements.


Misfire at idle and low rpm problems can be caused by a variety of mechanical problems. One of the most common causes of misfire at idle is often related to dirty or bad fuel injectors, while misfires at low rpm may be caused by bad sparks or lean fuel.

In either case, you need to contact your local mechanic to assess these problems. In some cases, engine misfires are relatively easy to identify and correct with the appropriate repairs.

References for cost estimators:

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