OBD2 Codes

Chevrolet P0300 – Meaning, Causes, Symptoms, & Fixes

P0300 Random/Multiple Cylinder Misfire Detected

What Does Chevrolet Code P0300 Mean?

  • P0300 definition: Random, Multiple 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 multiple 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 take your car into a shop to have it diagnosed as quickly and accurately as possible.

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Your Chevrolet 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.  P0300 indicates that two or more cylinders are experiencing misfires. 

Chevrolet P0300 Causes

Multiple 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 and/or spark plug wires
  • Ignition issues, including failing or damaged ignition coils 
  • Distributor failure 
  • Faulty fuel injector
  • Vacuum leak
  • Low fuel pressure
  • Camshaft and/or crankshaft sensor defective
  • Engine timing off
  • Leaking head gasket
  • Low engine compression
  • Poor quality fuel that is old or contaminated

Chevrolet P0300 Symptoms

  • Check Engine Light is on or flashing
  • Engine runs rough, hesitates, or jerks when accelerating
  • Drivers may not notice any adverse conditions when driving
  • In some cases, drivers may experience decreased fuel economy, fuel smell from exhaust, rough idling, or lack of power from the engine
  • Commonly associated with error codes: P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308

How Do I Fix Chevrolet Code P0300?

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.

Right shop, right price

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

How Much Does It Cost to Fix Chevrolet Code P0300?

P0300 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 P0300 code.

Possible Repair Costs for P0300

Once properly diagnosed, P0300 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

DIY Steps to Diagnose Chevrolet Code P0300

Engine code P0300 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 code P0300 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

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

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

STEP 1: USE FIXD TO ENSURE NO OTHER ENGINE CODES ARE PRESENT.

Use FIXD to scan your Chevrolet to verify P0300 is the only code present. If other codes are present, they must be addressed first.

STEP 2: CHECK FOR LOOSE CONNECTORS OR DAMAGED WIRING AT THE IGNITION COILS. 

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.

Worn and old spark plug wires are common causes of random misfires. Replace spark plugs and wires if needed and recheck for misfires. 

> How to replace spark plugs in 4 easy steps

> How to identify a fouled spark plug

> How to test spark plug wires

> How to gap spark plugs

STEP 4: CHECK TO ENSURE YOUR ENGINE IS GETTING THE PROPER AMOUNT OF FUEL.

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 fuel injectors: Make sure 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 ENGINE COMPRESSION AND LEAKDOWN TEST

If the ignition system and fuel system checks out, you may want to perform an engine compression test and leakdown test to see if there are any mechanical problems causing your misfire. 

Common mechanical problems that can cause misfires:

  • 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.

Common P0300 diagnosis mistakes

Loose fitting electrical connectors and broken or disconnected vacuum hoses are often overlooked. Oxygen sensor(s) are another common misdiagnosis for P0300.

Still Need Help Fixing Chevrolet Code P0300?

If you’ve followed the steps above and are still experiencing misfires or check engine code P0300, please contact the FIXD Mechanic Hotline if you’re a FIXD Premium subscriber or find a RepairPal certified shop near you to get the right repairs at a fair price.

Justin-Hughes

Recovering autocross and track day enthusiast. Once turned a VW Jetta into a pickup truck. Lives in a van down by the river. Dream car: 2001 Subaru WRC rally car.

Justin Hughes
Recovering autocross and track day enthusiast. Once turned a VW Jetta into a pickup truck. Lives in a van down by the river. Dream car: 2001 Subaru WRC rally car.

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    15 Comments

    1. The engine only misfires and shuts down when will you use the air conditioner we’ve replaced oxygen sensor number 2 on bank 1 and oxygen sensor number 2 on bank 2. Those were the codes that were kicking up. One day we were driving here with the air conditioner on and the check engine light started flashing vehicle started hesitating and sputtering and then died I had my diagnostic tool with me and it said multiple engine fire misfires. Could it be cam sensor in the distributor?

      1. i get a random po300 p0301 p0303 p0305 code light start to flash then car runs rough i delete codes then it come back a lil while after driveing again new plugs new coils

      2. I have a 2004 Chevy Silverado 4wd 5.3 keep getting codes for bank 1 and 2 to rich and p0300 for random engine misfire. Check engine light comes on intermittently and goes back off. Have a slight rough idle. Entire fuel system, evap system, plugs, wires, coil packs, maf and map have all been replaced within the last year. As well as catalytic converters. Tried new maf sensor fixed issue for about 4 months and replaced it again today after I had cleaned the old one to see if it made a difference which it did not. Not sure what else to try at this point pretty frustrated.

        1. I have the exact same problem on my 2001 Chevy 1500 5.3 liter just wondering if you have found the issue if so maybe you could give me a hand that would be great

        2. Check the chassis ground, Follow the small diameter wire from the battery ground side to where it is grounded on the chassis. (mine was under the R/F body mount ) Take the bolt out, clean the ground eyelets and use wire brush or emery cloth to clean off the frame. re-install the bolt and start the engine.

    2. My code reader brings up p0300 When I first drive the car it run about 75% power as i keep driving it it get worse it make a sound I would guess like a dryer sound but when I idle it stops can you help me figure it out

      1. May have bad catalytic converters.

        1. ^^^Yup, especially if you smell a rotten egg, fart, sulfur smell that’s definitely where I’d start

    3. This is a big problem with the 4.3s. Believe it or not but I had a customer come to me after having replaced all tune-up parts, all 02 sensors, fuel pump and the cat converter and it still ran the same way and had all the codes come back up. What I have found to be all of these problems was the distributor itself. I took a distributor out of a 2000 Chevrolet S10 I had here (which is an exact match) dropped it in and he’s still running it 4 months later. The only thing I can figure out is that the distributor over heats because there is no air getting to the back of the motor. There are 2 vent holes in the base of the distributor base and they are small little slits so they don’t let much air in to cool the inside of the distributor and parts inside. Hopefully this was helpful to everyone having these problems

      1. had this problem . you are close. check for up down play in distributer . found this by mistake. after changing everything you did. went thru four dist. before got one with no up downplay . truck runs like a brand new truck. let me know what you find.

    4. I have a 08 Chevy Suburban 5.3 with a PO300 misfire and the scanner says it’s in Cylinder 1 I’ve changed plugs and wires, ignition coil and fuel injector on cylinder 1 still no fix someone told me it could be the Catalytic converter’s so replaced that no fix saw that the injector on 1 had a crack in the wire so replaced the connection piece drove home the engine light was flashing Stability track light came on and would be very sluggish and shake on idle and light went off drove perfect for 50 seconds then back to how it was

    5. code reads that the Engine is misfire, 2002 Chevy silverado with 350,000 miles . will new spark plugs and wires help this? Looking to not drive until I get it fixed, open for suggestions. Husband died this is his truck, I will keep and fix but is it going to be expensive, on a fixed income.

      1. 98 4.3 silverado flashing check engine light rough running vibrating all of a sudden! What do I do

      2. Might try another distributor, they aren’t too expensive.

    6. I have a random misfire code mostly in wet weather. I have changed all the coils and wires and spark plugs and still have the same issue what am I missing .

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