OBD2 Codes

Chevrolet P0300 – Meaning, Causes, Symptoms, & Fixes

P0300 Random/Multiple Cylinder Misfire Detected
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Chevrolet Code P0300 Definition

Random/Multiple cylinder misfire detected.

What Does Chevrolet P0300 Mean?

Chevrolet code P0300 indicates that one or more cylinders are experiencing misfires. A misfire occurs when an insufficient amount of fuel is burning in a cylinder. The efficient burning of fuel is essential to engine operation as the combustion of fuel is what provides the energy to power the engine in your Chevrolet. A misfire from one or more cylinders can be caused by many reasons from a faulty ignition system, fuel system or internal engine failure. When P0300 occurs it should be fixed immediately as long term driving with engine misfires could cause consequential damage to the engine in your Chevrolet.  Many times P0300 occurs when there are worn out spark plugs, spark plug wires, or a faulty ignition coil.

Chevrolet P0300 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

Chevrolet P0300 Causes

(* = Most Common)

  • 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

Chevrolet Code P0300 Severity – Severe

 

Chevrolet code P0300 should be repaired immediately. Ignoring this error could result in ignition failure, catalytic converter damage, and unsafe/dangerous conditions while operating your Chevrolet.

Chevrolet Code P0300 Common Diagnosis Mistakes

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

Chevrolet Code P0300 Diagnosis Steps

Tools Needed to Diagnose:

  • Tools You May Already Have:
  • Tools You May Need (FIXD’s Top Picks From Amazon):
    • FIXD
    • Digital multimeter
    • 5/8in. Spark Plug Socket
    • Ratchet, sockets, and extensions
    • Fuel pressure gauge
    • Compression tester
    • Leakdown tester
    • Spark plugs
    • Spark plug wires

How To Diagnose Chevrolet Code P0300

  1. Use FIXD to scan your Chevrolet to verify P0300 is the only code present. If other codes are present, they must be addressed first.
  2. Check for loose connectors at the ignition coils or for damaged wiring. Look for loose engine ground wires as well. These can cause random misfire conditions. Tighten or connect where necessary.
  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.
  4. 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.
    • 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.
  5. 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. Some common mechanical problems that cause misfire can be:
    • Broken valve spring
    • Broken piston ring
    • Worn valve guides
    • Burned valve
    • Timing chain or belt skipped tooth and engine is off time.

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13 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. 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.

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