Causes and Fixes P0303 Code: Cylinder 3 Misfire Detected

How to fix P0303 Code: Cylinder 3 Misfire Detected
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An engine misfire is when a cylinder has an incomplete combustion ignition or has no combustion in the cylinder.
Each cylinder needs the correct air-fuel mixture and Spark to complete combustion.
If the vehicle only has a P0303 Code, then the components on that cylinder should be tested.
A cylinder's individual components would include the coil, injector, spark plug, and spark plug wire.
If there are other engine codes, then there may be other issues.
For example, multiple misfire codes (P0300) can be caused by low fuel pressure, bad sensors, vacuum leak, and more.
Possible Causes of a P0303 Code
Bad Spark Plug or Spark Plug Wire
Bad Coil
Bad Fuel Injector
If Equipped, Distributor Cap
How to Troubleshoot a P0303 Code:
The main things to check for is Spark and Fuel on the Cylinder #3.
Locate Cylinder #3
Check Spark Plug Wires and Coil
Check for Spark
Check Spark Plug
Check Fuel Injector Wiring
Test Fuel Injector
By using this information user assumes all risk of use.

[@2010msilva6]

I changed my spark plugs and coil still nothing. It goes away then comes back in the morning.

[@coolghoul9]

Valve cover leak?

[@flyingblind19]

Swapped spark plugs and fuel injectors. Swapped the coils around and still getting misfire on number 3. Could it be a piston damaged or is it probably the wire ?

[@HVAC_Mechanic]

It could be a mechanical issue, such as a cracked head or cylinder/piston, but that is fairly rare. If the components are good, I would test the wiring.

[@josephcasteel9252]

2003 Buick century 3'1 3 missfire good spark plugs and wires missing real bad on idle I smell fuel and gas gauge will go up and down when I'm driving

[@soulysznnnn]

intake and exhaust stems? is there smoke when running the engine and open the oil cap

[@terencejackson3480]

​@@soulysznnnnsame situation & I'm seeing smoke when opening the oil cap. Any ideas?

[@soulysznnnn]

@@terencejackson3480 blow bye, so could be a piston or burnt valve if it’s not the ignition coil or spark plug

[@danysaade2286]

My 2022 Chevy suburban been in the dealer almost a month and they didn’t know
We change 16 lifter camshaft spark plug Injector
What next ?

[@jebb3620]

tell them to fix your vehicle.

[@nightmareedge657]

Faulty wiring

[@guerrachula9259]

I have P0303 and P0305 code and replaced the fuel injectors but still having trouble with acceleration after 50mph.

[@HVAC_Mechanic]

Since it is more than one cylinder, I would replace any in-line fuel filters and do a fuel pressure test.

[@RJ-ex9on]

Could be you throttle body.Replace or take off throttle body and clean it especially in the back area once you take it off ..Disconnect battery ground if you proceeded to do so.