P0303 – Meaning, Causes, Symptoms, & Fixes (2022)

What Does P0303 Mean?

  • P0303 definition: Cylinder 3 misfire detected.
  • Issue Severity:SEVERE – Stop driving immediately.
  • Repair Urgency:Fix this code immediately (same-day if possible) to avoid ignition failure, catalytic converter damage, and dangerous conditions.
  • Diagnosis: A cylinder 3 misfire can be caused by anything from faulty spark plugs to low engine compression. Because there are so many variables that could cause a misfire, the best cost savings is to find a trustworthy repair shop to diagnose code P0303 as quickly and accurately as possible.

P0303 – Meaning, Causes, Symptoms, & Fixes (1)

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Your vehicle moves when gasoline is burned and power is generated inside a chamber known as the cylinder. Most engines have a 4, 6, or 8-cylinder engine, where more cylinders typically mean more power. Power is generated by pistons that move up and down while fuel is ignited at very specific times. A misfire typically occurs when the timing of this ignition is off. P0303 indicates that cylinder number 3 is experiencing misfires.

Table of Contents

Code P0303 Causes

Cylinder 3 misfires can be caused by many reasons from a faulty ignition system, fuel system, or internal engine failure. The most common reason for this to happen is faulty or worn-out spark plug coil packs, especially if it’s been a while since you had a tune-up.

  • Faulty or worn spark plugs
  • Faulty spark plug wires or coils
  • Distributor failure
  • Faulty fuel injector
  • Vacuum leak
  • Low fuel pressure
  • Camshaft sensor defective
  • Crankshaft sensor defective
  • Engine timing off
  • Leaking head gasket
  • Low engine compression
  • Poor quality fuel

P0303 Symptoms

  • Check Engine Light is on
  • Check Engine Light flashing
  • Engine runs rough and shaking
  • Lack of power from the engine
  • Fuel smell from the exhaust
  • Hesitations/Jerking when accelerating
  • Commonly associated with code P0300

How Do I Fix Code P0303?

With a misfire fault, the first step is to get it diagnosed to figure out what is causing the engine to misfire.If your vehicle is misfiring and you’re not comfortable diagnosing this issue at home, we recommend finding a RepairPal certified shop nearby to pinpoint the problem and give an accurate estimate for repairs.

These shops can not only help you figure out what’s going wrong before you waste time and money on the wrong parts, but they also offer a minimum 12-month, 12,000-mile warranty and stand behind all their estimates with guaranteed fair pricing.

> Find a RepairPal Certified Shop Near You

How Much Does It Cost to Fix Code P0300?

P0303 can be caused by anything from old spark plugs to vacuum leaks to poor engine compression. It’s impossible to give an accurate estimate without properly diagnosing the issue first.

If you take your car to a shop for diagnosis, most shops will start with an hour of “diag time” (the time spent in labor diagnosing your specific issue). Depending on the shop’s labor rate, this typically costs somewhere between $75-$150. Many, if not most, shops will apply this diagnosis fee to any required repairs if you have them perform the repairs for you. From there, a shop will be able to give you an accurate estimate for repairs to fix your P0303 code.

(Video) Engine Misfire? Trouble Code P0303 Meaning, Diagnose Spark Plugs & Ignition Coils

Right shop, right price

(Video) P0303 Explained - Cylinder 3 Misfire (Simple Fix)

We've partnered with RepairPal to recommend certified and trustworthy shops in your local area.

  • Upfront cost estimates
  • Minimum 12-month, 12,000-mile warranty
  • Fair price guarantee

Other Possible Repairs for Code P0303

Once properly diagnosed, P0303 may require one or more of the following repairs to resolve the underlying issue. These prices are based on national averages and include parts and labor. Your cost may differ depending on your location and type of vehicle.

  • Spark plugs: $66-$250
  • Ignition Coils: $230-$640 (some cars require Intake manifold removal)
  • Spark plug wires: $180-$240
  • Fuel injectors: $1500-$1900
  • Vacuum leak: $100-$200
  • Fuel pump: $1300-$1700
  • Fuel pressure regulator: $200-$400

Steps to Diagnose Code P0303:

Engine code P0303 could be caused by a number of things, including faulty spark plugs, faulty ignition system, distributor failure, and more. If you’d like to try to fix this fault code at home without throwing money at parts, you’ll want to follow the steps below for proper diagnosis. Keep in mind this is an intermediate-level diagnosis and repair and not recommended for beginners. Diagnosis requires more specialized equipment beyond what the FIXD Sensor can provide and it can be a time and labor-intensive process for inexperienced DIYers.

DIY difficulty level: Intermediate

(Video) How to Fix P0303 Engine Code in 3 Minutes [2 DIY Methods / Only $4.11]

This repair requires mechanical knowledge and is not recommended for beginners.

Tools/parts needed(our top picks from Amazon):

Step 1: Use FIXD to scan your vehicle to verify P0303 is the only code present. If other codes are present, they must be addressed first.

Step 2: Check for loose connectors at the ignition coils or for damaged wiring (specifically cylinder 3). Look for loose engine ground wires as well. These can cause random misfire conditions. Tighten or connect where necessary.

Step 3: Check the condition of your spark plugs and spark plug wires.

If your vehicle is equipped with individual coil packs instead of spark plug wires, start by removing the cylinder 3 coil and swapping it with the cylinder number 4 coil. If the misfire moved to cylinder number 4 (P0304), then you have determined that the coil pack is faulty and needs replacement.

You can do the same test with the spark plug, i.e., move cylinder 3 plug to say cylinder 2 and if the misfire is now P0302 then the plugs are at fault. Replace spark plugs and spark plug wires/ignition coil packs if needed and recheck for misfires. (How to identify a fouled spark plug, How to test spark plug wires, How to gap spark plugs,How to replace spark plugs, How to swap ignition coils)

Step 4: Check for fuel system issues.

If you have determined that your ignition system is operating correctly, there may be a problem within your fuel system that is causing the random misfires. The following should be checked to ensure the engine is getting the proper amount of fuel:

  • Check fuel pressure. Low fuel pressure can cause intermittent misfires on multiple cylinders. When the pressure is below the specification, the engine does not receive the proper amount of fuel and will start to lean misfire. The fuel pump or fuel pressure regulator could be the source of the low fuel pressure. (How to check fuel pressure).
  • Check that the fuel injectors are functioning properly and activating. Random misfires can be a sign of faulty or clogged fuel injectors that need to be replaced. Also, check that the fuel injector wiring is not damaged and is connected properly. (How to check fuel injectors by ear, How to check fuel injectors with a digital multimeter).

Step 5: Perform an engine compression and leakdown test.

If the ignition system and fuel system checks out, you may want to perform an engine compression test and leak down test to see if there are any mechanical problems causing your misfire. Some common mechanical problems that cause misfire can be:

  • Leaking head gasket
  • Broken valve spring
  • Broken piston ring
  • Worn valve guides
  • Burned valve
  • Timing chain or belt skipped tooth and engine is off time.

Code P0303 Common Diagnosis Mistakes

Loose-fitting electrical connectors and broken or disconnected vacuum hoses are often overlooked.

Still Need Help Fixing Code P0303?

If you’ve followed the steps above and are still experiencing misfires or check engine code P0303, please contact the FIXD Mechanic Hotline if you’re a FIXD Premiumsubscriber orfind a RepairPal certified shopnear you to get the right repairs at a fair price.

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FAQs

What causes number 3 cylinder misfire? ›

Cylinder 3 misfires can be caused by many reasons from a faulty ignition system, fuel system, or internal engine failure. The most common reason for this to happen is faulty or worn-out spark plug coil packs, especially if it's been a while since you had a tune-up.

How do I fix error code P0303? ›

How serious is a cylinder 3 Misfire? ›

A misfire occurs when there is an insufficient amount of fuel burning in a cylinder. Since the way the engine runs relies heavily on the proper functioning of its cylinders, a misfire can cause big problems. That's why the OBD-II code P0303 is considered a serious issue and should be addressed immediately.

Can I drive with a cylinder 3 Misfire? ›

Driving with a misfiring cylinder is potentially dangerous. If you lose power while driving or a second or third cylinder goes out, this can cause you to get into a car accident, possibly injuring you and others around you.

Can a misfire correct itself? ›

However, most misfires dissipate, and your engine regains its normal speed after a second or two. But even a single misfire is usually a sign that something else is wrong and that more misfires will likely occur in the future.

Can a bad catalytic converter cause a p0303 code? ›

For example, the issue can stem from a faulty spark plug or wire, which in the grand scheme of things is relatively easy to repair. However, the error code may also occur because of a faulty catalytic converter or defective computer system, which can vary in expense.

How do I find a cylinder 3 Misfire? ›

P0303 Explained - Cylinder 3 Misfire (Simple Fix) - YouTube

How much is it to fix a cylinder 3 Misfire? ›

However, it's dangerous to drive with a malfunctioning cylinder, so have your vehicle diagnosed and treated before you get back on the road. The cost of repair and replacement can range from anywhere between $100 to $1000, depending on the reason for the misfire.

Will a misfire damage my engine? ›

If left untreated, a cylinder misfire can lead to significant engine damage. Worse, if you experience a bad misfire while driving, it could result in an accident. This is why it's important to treat engine misfires as soon as you detect them.

How much is it to fix a cylinder 3 Misfire? ›

However, it's dangerous to drive with a malfunctioning cylinder, so have your vehicle diagnosed and treated before you get back on the road. The cost of repair and replacement can range from anywhere between $100 to $1000, depending on the reason for the misfire.

How do I find a cylinder 3 Misfire? ›

P0303 Explained - Cylinder 3 Misfire (Simple Fix) - YouTube

Is it OK to drive with a P0300 code? ›

Is it OK to drive with a P0300 code? No. You need to immediately fix the misfiring to prevent damage to the catalytic converter and internal engine components. So, you should never drive the car when it shows a P0300 code.

Does P0300 clear itself? ›

Once the problem is repaired or no longer detected, the misfiring code will clear itself after some driving.

Videos

1. Fixing a cylinder misfire - Check Engine Light - Cylinder Misfire Code - P0303
(The Daninator)
2. SIMPLE MISFIRE FIXED - P0303 - Auto Repair (Ver.2)
(HouseCallAutoRepair)
3. Comprehensive Guide to Diagnose and Fix Misfires - P0301 P0302 P0303 P0304 P0305 P0306 and P0300
(Build It Make It)
4. How to Fix a Random Engine Misfire in Your Car (Code P0300)
(Scotty Kilmer)
5. How to Fix NISSAN P0303 Engine Code in 3 Minutes [2 DIY Methods / Only $4.11]
(nonda)
6. Fixing Misfire or P0303
(Autotipsca)

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