If you’re having engine trouble and go in for a diagnostic check, a P034 OBD-II diagnostic code or “Cylinder 4 misfire detected” is a common issue.
This is just one of a number of diagnostics codes that point to the 4th cylinder not getting enough fuel or something wrong with the lean/rich mixture of fuel/air.
And, you’ll likely hear actual misfires, as your engine skips cylinder four – or over-combusts in it. However, repairing the issue can be more difficult, as several issues can cause the problem.
For example, spark plugs, fuel injectors, the vacuum system, the distributor, engine timing, exhaust, a leaking head gasket, poor quality fuel, sensors in the crankshaft and camshaft can all cause the issue.
This means that fixing a cylinder 4 misfire will cost anywhere from $150 to $3,000+. However, the most common issues are spark plug and fuel injector failure, which normally costs $150-$450 to fix. Here, parts typically cost about $50 while labor can be anywhere from $50-$500.
The table below shows a quick price comparison of cylinder 4 misfire repair cost estimates from reputable suppliers:
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Engine Cylinder Misfire Repair Cost Breakdown*
The cost of repairing a cylinder misfire will heavily depend on what’s causing the issue.
For example, a fuel injector will cost about the same or a bit more to repair as a spark plug issue. However, if you have to replace a timing chain, you’re looking at over $1,000 in costs.
The most common issue causing a cylinder 4 misfire is a spark plug issue. That’s either the spark plugs, the ignition coil, or a leaking gasket flooding the spark plugs with oil.
But, if you want to replace spark plugs, costs should look something like this:
|Vehicle||Spark Plug Cost (per set)||Labor Cost|
*Note: Prices are estimates and were correct at the time of writing (June 2023). Cost estimates may have changed since, our figures should be used as a starting point for your own research.
What Is A Cylinder 4 Misfire?
Engines use a combustion chamber attached to cylinders (4, 6, or 8 depending on your engine) to create mechanical force that moves the car.
Here, the combustion force rotates the cylinder, resulting in that mechanical force. However, in order to rotate properly, the cylinder has to line up with the combustion – including the fuel injection and air injection at the right time.
If something goes off, the engine will misfire by either not rotating the cylinder, rotating too much, or with too much force.
That issue is typically caused by something being off with the lean/rich system, or the mixture of exhaust and fuel in the combustion chamber. However, it can also be caused by ignition of that mixture – which is actually the most common issue.
This is especially true when you have a misfire issue local to a single cylinder. It’s most likely to be an issue with the spark plus associated with that cylinder – or with the fuel injector associated with that cylinder.
Cylinder 4 Misfire Repair Pricing Factors
Fixing a cylinder 4 misfire detected code may be a very simple process. For example, you may have a valve jammed open. On the other hand, it might mean your catalytic converter is going out and requires replacing.
For this reason, the cost of repairing the issue can vary considerably.
Cause of the Misfire
There are over a dozen common causes for cylinder misfires. However, the fact that the misfire is located in a single cylinder means that it’s more likely to be either a spark plug issue or a fuel injector issue. However, those are not the only options.
Here, spark plugs, ignition coils, distributors, fuel ignition, fuel filters, and vacuum seals are likely to cost $150-$500 to repair. On the other hand, leaking gaskets, timing chain issues, vacuum system failure, or exhaust issues are likely to be $1,000-$1,500.
And some issues like a failed catalytic converter or problems with the crankshaft or camshaft are likely to be $2,000-$4,000.
So, you’ll always have to figure out what’s gone wrong with the vehicle before you can figure out how much it will cost to fix. However, on average, fixing this error code is about $350 for a spark plug or fuel injection replacement.
Cost of Labor
The cost of labor is sometimes the largest part of the cost of repairing a cylinder misfire. That’s especially true if you have an issue like a timing chain problem. In this case, you might pay up to $1,500 in labor.
However, for most jobs, you’ll need 1-4 hours of your technician’s time. At a standard mechanic, you’ll typically pay $50-$75 in most of the United States, $94-$150 in most chain shops, and $100-$210 at most dealerships.
However, if you live in areas with a higher cost of living, like Seattle, it’s likely to cost around $200 per hour for a basic mechanic.
Most shops will charge $60-$200 for a diagnostic check on your vehicle. Some, especially dealerships, will provide it for free. In addition, if you then have work done in the same location, you can typically get as much as 60% of that back as a discount on the work done.
So, if you pay $120 for a diagnostic and then have a $350 bill for new spark plugs, you might only have to pay $278 for the parts and labor. Still, diagnostics fees can be quite high.
Make and Model
The make and model of your car will impact the cost of parts, the availability of parts, and the cost of labor. For example, if you go to a dealer, different dealerships charge vastly different hourly rates.
In addition, your mechanic may charge you a different rate based on how familiar they are with the vehicle. That’s also true depending on the onboard diagnostic system.
The make and model of the car also impacts the costs of parts. For example, BMW parts are normally relatively affordable but labor is expensive. Honda parts are usually expensive but labor tends to be relatively cheap.
So, you’ll have to ask around and get quotes if you want to know how much your car costs to fix.
Replacement Parts Needed
Your cylinder misfire could be the result of a $4 seal. On the other hand, it could be a failed catalytic converter, which can cost over $1,000 in parts. In addition, you can spend significantly different sums on the same parts.
Buying OEM spark plugs from a dealer will typically cost about $100-$150 but up to $350. On the other hand, aftermarket spark plugs can cost as little as $25 for the set. You’ll want to balance quality and cost – and dealers will never let you bring your own parts – but those factors will greatly impact your final bill.
4 Symptoms Of Cylinder 4 Misfiring
If your cylinder 4 is misfiring, you’ve probably noticed a check engine light. In fact, if you know that it’s a cylinder 4 issue, you’ve probably run the diagnostic and gotten back an error code.
However, there are other symptoms that suggest the cylinder is misfiring – although all of these symptoms could apply to any cylinder, in any bank, or all of the cylinders.
1. Noises from the Engine
Coughing, spluttering, and interrupted engine rotation are always a sign of engine misfiring. You could also hear what sounds like increased noise or an increased frequency of vibration in the normal engine sound.
In some cases, a misfiring cylinder will also sound like one part of the rotation is louder than the rest.
In any case where your engine changes the sound it makes, have it looked at. Engine misfires, loose chains, and other issues can all result in permanent damage to your engine, which could cost thousands of dollars.
Having the issue looked at and fixed before that damage happens is the best option.
2. Poor Acceleration
Poor acceleration, power loss, and increased fuel usage to achieve the same speed or power are all symptoms of a misfire. However, they can also be symptoms of any other issue with the fuel injection or exhaust system.
No matter what’s wrong, though, if you’re losing power while driving, continuing to drive without fixing the issue could make the problem worse. Therefore, it’s always a good idea to take your vehicle in for a checkup.
3. Exhaust Smoke
Visible exhaust smoke is always a sign that something is wrong. Here, it typically means that you’re either leaking oil from the head gasket into the fuel injection chamber (white smoke), or that the exhaust is having problems.
In either case, fixing the issue as quickly as possible will prevent further damage and a fine.
4. Rough Idle
When your car is parked and idling, the idle should remain relatively even and smooth. If it’s not, and if has sudden roars, dips, or interruptions, it’s known as a rough idle.
This always means something is wrong, although the issues could be with the fuel injection, exhaust, or even the crank and camshaft.
How Do You Repair Cylinder 4 Misfiring?
The first step to repairing a cylinder 4 misfire is to figure out what’s wrong. That should mean inspecting the vehicle to determine what the cause of the problem is.
- Check the spark plugs. Taking them out and looking for oil or signs of damage
- Inspect the fuel injection
- Take out the fuel filter and look for clogs and built up debris
- Inspect the exhaust system and check if you smell the exhaust while the vehicle is idling
In most cases, if you have a cylinder 4 issue, it’s a spark plug issue. So, this guide will walk you through changing the spark plugs.
Things You’ll Need
- Disposable gloves
- Ratchet and socket set with an extension
- Replacement spark plugs
- Spark plug wrench or deep socket spark plug wrench depending on your vehicle
- Park your car on a flat and level surface. Turn off the engine and take the key out.
- Open the hood and remove the battery from the left negative post and tuck it up out of the way.
- Take a photo of the manifold so you can see where everything goes.
- Remove the wires from the manifold. You may also have to remove the manifold cap before you can reach those wires. Here, you’ll simply have to take off the bolts on the manifold cover. You may also have to remove the valve cover – although it’s unlikely as only a few vehicles hide spark plugs under the valve cover.
- Use a spark plug wrench or a ratchet to ratchet out the spark plugs, one at a time.
- Inspect each one for damage such as burn marks or oil. If you have oil on the ends, you have a gasket or a valve seal issue you’ll have to fix by taking off the manifold and re-doing the seal.
- Insert and screw in the new plugs – there’s one spark plug for each cylinder. You should always change all of the spark plugs and not just the one on cylinder four.
- Replace the wiring firmly, ensuring that it lines up with the original placement.
If you still have questions about repairing a cylinder 4 misfire, these answers should help.
How Serious is a Cylinder 4 Misfire?
A cylinder 4 misfire is a very serious issue and you should try to have it fixed immediately. Here, ignoring the problem can result in catastrophic damage to the engine or increase the total cost to fix.
In addition, cylinder misfire issues always increase the cost to operate your vehicle, which means that even if the issue doesn’t get worse, you will spend more on fuel for what could be a relatively inexpensive fix.
What Causes a Cylinder 4 Misfire?
There are a lot of reasons the cylinder 4 could misfire. However, some of the most common include:
- Vacuum leak issues
- Emissions problems such as the EGR system
- Ignition issues
- Spark plug problems
- Leaking gaskets
- Fuel injector clogs
- Damaged fuel filters
- Faulty sensors
You’ll need an inspection to determine which issue it is.
Here, most technicians will start with the most likely issues first and will look at the spark plugs, fuel injection fuel filter, sensors, and ignition in that order.
Will Driving with a Misfire Damage My Engine?
Driving with a misfiring engine will always damage the engine. The longer you leave it alone, the more likely you are to have permanent engine damage.
For example, changes in pressure in the combustion chamber can warp or crack the combustion chamber – which means rebuilding the engine. For that reason, the sooner you deal with your P034 code, the better.
A cylinder 4 misfire code can occur because of a large number of issues. However, the most common are spark plug failure and fuel injector failure. These issues will typically cost $150-$350 to fix – or around $500+ if you go to the dealer. However, it’s important to check other potential causes of the misfire, as changing parts out might not fix your misfire issue.
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