OBD2 Codes

Jeep P0300 – Meaning, Causes, Symptoms, & Fixes

P0300 Random/Multiple Cylinder Misfire Detected

What Does Jeep 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 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. Jeep P0300 indicates that two or more cylinders are experiencing misfires. 

Jeep 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

Jeep 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: P0301P0302P0303P0304P0305P0306, P0307P0308

How Do I Fix Jeep 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 Jeep 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 Jeep 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 Jeep 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

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


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


Look for loose engine ground wires as well. These can cause random misfire conditions. Tighten or connect where necessary.


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


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


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 Jeep 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 Jeep 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.


Lifelong automotive enthusiast with a soft spot for offroading. Wrencher turned writer, but I still love to tinker on just about anything with an engine. Dream car: tie between a ‘71 Hemi ‘Cuda and a ’91 GMC Syclone. #GirlDad #SaveTheManuals

Jeffrey N. Ross
Lifelong automotive enthusiast with a soft spot for offroading. Wrencher turned writer, but I still love to tinker on just about anything with an engine. Dream car: tie between a ‘71 Hemi ‘Cuda and a '91 GMC Syclone. #GirlDad #SaveTheManuals

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  1. I have a missfire and p0300 code. Changed spark plugs coils and cleaned out fuel injectors. Checked the gas tank and for any leaks but nothing is wrong. I disconnected the o2 sensors and still have the missfire. Also checked out the air intake . What could it be ??

    1. Have the same problem did you figure it out?

    2. Do you figure it out? I was told the crankshaft sensor b UK t haven’t done it yet

      1. I’ve been having the same issue, p300 and p0052 codes. I had replaced the plugs, wires, and coil. I used a reader and found out it was cylinder 1 and 6 so I replaced those plugs again. I still have the same issues however. My next stop is the O2 sensors.

        1. I have a 2017 jeep with a misfire replaces spark plugs, fuel injectors, coils, cat and o2 sensors. That didnt do it. I inspected again and came to the conclusion it has to be the head.

    3. Does it have a backfire? Could be a lifter

  2. I. Hanged my spark plugs and my ignition coils and the Jeep still registered cylinder 1 misfire and multiple misfires. The next thing to do is change the fuel injectors and see what happens. Fingers crossed !!

    1. The engine light on my ’09 Jeep Grand Cherokee came on Sunday afternoon. On my way to Firestone this morning to get it checked out, the engine light started flashing and the vehicle felt like it was going to stall. I pulled over to an O’Reilly’s which was on the way. The OBD II scan presented O2 sensor and multiple misfires, P300, fault codes. So I chanced it and continued my trek. Firestone confirmed the finding. They replaced 6 spark plugs, 2 O2 sensors and performed a fuel cleaning. I’m good now…

      1. I have a 2009 jeep liberty and i get a code p0300 and check engine light flashing and i replace the exhaust valve and intake valve on both head new head gasket with new timing chain new fuel pump and fuel injector spark plug and plug wire and ignition coil and throttle body and i still get the check engine light flashing and the code p0300 and i took off the exhaust out and the catalytic converter on the passenger side was bad and i have new o2 sensor and wanted to know if it could me the catalytic converter and it will start right up the first start and when i turn it off and turn it back on it takes a while to start but when i but my foot on the gas pedal a little it will start right up it has new fuel pump and fuel injector and the RPM stays at 2 rpm

        1. CPS (camshaft position sensor) was my issue on P0300 (multiple cylinder misfire). If the code doesn’t signify a specific cylinder (P03021, P0302, etc), it usually has something to do with timing as not all plugs or injectors normally go out at the same time. On newer TJ’s (6-speed manual), it is pretty easy to get to and check. Underneath the passenger side connected to the bell housing. One 10mm bolt to undo. It could just be super dirty like mine was from oil and dirt seeping in for 12+ years. Cheap to replace, but can cause havoc as it basically makes your vehicle un-driveable when it goes out, unless you want to risk doing major damage 😉 If it shimmies and sputters, especially around 1800-2000RPM, I would check that little bugger out.

  3. I have a 2008 Jeep Liberty, it’s saying a misfire at cylinder 6 so I replaced all coils & plugs, and even changed all 4 sensors bank 1 and bank 2 up stream and down stream, it doesn’t have a problem starting but it still runs rough going up hill, like the rpm went all the way to 5 then it finally kicked in and took off really fast, ANYONE KNOW WHAT ELSE I COULD DO?? PLEASE HELP!

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