Full Guide on P0305 Cylinder 5 Misfire(Fix, Causes, Diagnosis & Symptoms)

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Are you having a p0305 error code? It’s not unusual for most persons. The p0305 code is specifically a cylinder 5 misfire and there are a lot of factors to could result or lead to it

In this post, we are going to discuss every bit of it.

That is ranging from causes, diagnosing the problem, identifying the symptoms and fixing them.

So here are the sub-areas we will cover in this post and we will try as much as we can to update and include more information with time.

Subtopics for this article:

  • What Does P0305 Mean?
  • P0305 Cylinder 5 misfire BMW
  • What is a misfire in a Car?
  • Car Combustion Cycle- 4 stroke engine parts
  • 3 Common Misfire causes
  • P0305 Symptoms and Diagnosis
  • Cylinder 5 misfire repair cost

Cylinder 5 Misfire – What Does P0305 Mean

What P0305 means?

This is a specific misfire in your 5th cylinder before worrying too much where you do explain what does possibly means for you and your engine

P0305 is a specific code for the cylinder 5 misfire, since this code in the 5th cylinder, that means it only applies to v6, v8, and v12 Engines.

Let say to take BMW for instance.

P0305 BMW code (P0305 Cylinder 5 misfire BMW)

A P0305 BMW code will mean that the car cylinder 5 is misfiring steady or at a random pace.

If this occurs, you have to check for intake leaks and no leaks are found then move on to find ways to replace your spark plugs on the cylinder.

Don’t get confuses here will talk about how to identify each problem and the causes of cylinder 5 misfires.

So to get into all that lets first look at the meaning of misfire.

Read Also About Flashing Check engine Light and  Blinking Cruise Control Light

What is a misfire in a Car?

A misfire is the desynchronization of the combustion cycle within the car engine. 

You can also say that a misfire is a symptom that occurs when the car engines combustion cycle is either to fast or too slow.

Car Combustion Cycle ( 4 stroke engine parts)

There 4 main stroke combustion cycle within a car and if your car is not made before 1980 then know that it has 4 stroke combustion cycle which are:

  1. Intake 
  2. Compression
  3. Power 
  4. And Exhaust 

So what happens here that your cylinder intakes the fuel oxygen mix, the mix is then compressed, the spear plug ignites the mix to get power and finally the cylinder opens to release the exhaust.

2 stroke engine diagram

The requirements for Combustion.

Combustion reaction requires 3 elements which are:

  1. Oxygen 
  2. Fuel
  3. And Spark

The intake stroke introduces oxygen and fuel. Then the power stroke provides the spark.

What could cause a misfire on one cylinder?

When any of these 3 elements or component above (oxygen, fuel, and sparks) are messed up or worse, the process gets out of the sink and then that is when you get this p0305 error code, indicating a cylinder 5 misfire.

Though the above 3 causes might be the common reason for a misfire for this case, there are a lot of more other reasons for misfire and we are going to look into some of the common misfire causes below.

3 Common Misfire causes

#1- Air Fuel Mixture Component 

The car engine requires a very specific mixture of fuel and oxygen, so if for a chance there happens to be a vacuum leak somewhere in the car or vehicle; then it could not be getting enough oxygen for that mixture to enable the car engine function properly.

So if you have ever asked yourself the question below then you should know the answer by now:

“Can a vacuum leak cause a single cylinder misfire?”

Then yes is the answer. A vacuum leak can be the cause of a single-cylinder misfire.

And some of the common vacuum Leaks that can cause this are:

  • i) a crack in the hose
  • ii) a leak in the hose
  • iii) or an air intake leak

#2- Fuel Leak or Congestion  component 

The next causes of misfire are a fuel leak or congestion component. This usually has to do with the fuel filter or the fuel injector.

To rectify this problem, I suggest you start by changing the fuel filter first because it is a cheaper fix that will cost around $25 to $70.

Off which replacing the fuel injector is a little more expensive and it is a more complicated electronic device which will cost anything around $600 to $1200 to fix.

#3- Ignition Coil /Spark Plug Component

The final cause of a misfire is an ignition coil or spark plug element. The good thing about this is that there is a super-easy way to check this.

When you go to the car engine you can simply switch one ignition coil from one cylinder to the other.

Don’t worry if you don’t know how to switch ignition coil, watch this video below to learn how to replace ignition coils 

How to replace ignition coils

After you have switched those ignition coils, go ahead and grab your OBD2 Scanner which you can get for cheap on Amazon here.

Mind you any good OBD2 scanner will work here. 

So when you scan the car and you notice that the p0305 code is changed to p0304 then you should know it is an ignition problem and that means you have to replace the ignition.

If it is not the ignition, then it is the spark plug cheap is cheap to fix.

Spark plug change cost

The spark plug cost anywhere around $10 to $100 depending on your car for the parts only 

Whereas ignition coils cost anything around $240 to $360 dollars for parts alone and labor cost will be around $60 to $77 dollars.

When you take out a spark plug be sure to check out the other spark plugs as well to be sure others are not bad.

If it’s just one plug that is affected then you are very much good to drive and enjoy your ride, but if there are multiple plugs affected then I will suggest you take your car to a trusted mechanic because it could be more serious than you think. 

Watch the video below to learn how you can change or replace the car spark plugs yourself.

How to Replace spark plugs Ultimate Guide

Code P0305 Common Diagnosis Mistakes

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

Code P0305 Diagnosis Steps

When running P0305 diagnostic text on your car the following tools are must-have diagnosis tools:

These tools are all available on Amazon, just click each one to check out the current price.

Cylinder 5 misfire repair cost

The cost of repairing a cylinder 5 misfire not fixed. It will depend on the exact cause of the misfire in the first which could range from anywhere around $25 to $77 for fuel filter related problem.

And $100 to $1,200 for fuel, injector problem, Ignition Coil and Spark Plug problems.

Please refer to each case above to see the cost specified per case.

P0305 Symptoms (Diesel engine misfire symptoms)

There are a lot of signs and symptoms that your car will exhibit to when indicating a P0305 error and the following are some of the common ones:

  • Solid check engine light Comes on
  • Fuel smell from the exhaust
  • Check Engine Light is on
  • Check Engine Light flashing
  • Engine runs rough and shaking
  • Lack of power from the engine
  • Hesitations or Jerking during acceleration

How Bad is P0305 Code? ( When P0305 cylinder 5 misfire detected)

Code P0305 Severity – Severe    

Do not try to ignore a P0305 code, it requires an immediate action to prevent further damage to the car.

Overlooking this error could lead to ignition failure, catalytic converter damage, and unsafe/dangerous conditions while operating the vehicle.

Related Article on how the could harm your car can be found here.

Conclusion On Code P0305 Cylinder 5 Misfire

P0305 which is a cylinder 5 misfire problem can cause by so many reasons which could be spark plug wires, bad fuels, or any other air intake components or even a mechanical problem within the combustion cycle.

And we have stated the 3 most common and the easiest to fix. All other cylinders 5 misfire issues will most likely require an expert or a real mechanic. 

So check the 3 out yourself first, before going to a mechanic. Hope this was helpful? Please feel free to share the article if it helped you.

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