Q: P0304 Misfiring on Cylinder 4
My truck has been misfiring on the number 4 cylinder. And I have changed the coil pack and plug which has voltage across the plug of the injector. I’m also getting this code P0304. It use to come on periodically, but now the code stays on permanently. Do you know how to fix this?
Recommended Services
| Fuel Injector Replacement | $400.56 - $3968.30 | Get a Quote |
| Engine is misfiring Inspection | $94.99 - $114.99 | Get a Quote |
Hello. If the spark plug and the coil have been replaced, then a compression test needs to be done. It is common for the valve seat to fail and cause this. When it fails, it causes low compression which then causes the misfire. If the compression is fine, then it is possibly a fuel injector issue, but that is not common for this vehicle. If you want to have this fixed, consider YourMechanic, as a certified technician can come to your home or office to diagnose the misfiring problem and resolve the issue.
The statements expressed above are only for informational purposes and should be independently verified. Please see our
terms of service
for more details
Get an instant quote for your car
Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing
What others are asking
Car stops accelerating, motor stalls, what can I do?
Before the advent of modern computer controls, the driver of a vehicle was in direct connection with many of the systems they were controlling. Power accessories (locks, windows, etc) were directly linked to the switches at the driver’s finger tips....
What seat belt parts have to be replaced after a crash?
Countless hours are spent designing and implementing safety features in modern vehicles, so the vehicle contains a considerable number of safety measures to ensure occupant safety. Seat belts are one of the few safety features that doesn’t require replacement after...
Leaky oil valve
My guess is that you mean you have a leaking valve cover. This is a pretty straightforward repair that can be handled by a professional, such as one from YourMechanic. They can come to your home or office to inspect...
Honda Civic with screaming timing belt when cold and wet
You probably need a fan belt. Timing belt is inside the timing cover and it has cogs on it and it can't squeal because it's got cogs and it can't slip. If it groans, it means that the timing belt...
Car runs rough and shuts off - 1990 BMW 750iL
Without some additional symptoms, this is hard to say. If the car runs smoothly when warm, this would reflect a "cold start" problem with the engine. If the transmission shifts harshly either cold or hot, the transmission may need repair...
Keeps overheating and I've already got the radiator flushed and the replaced the thermostat
Hi, thanks for writing in. You will need to have the cooling fan clutch checked to see if it is working properly. The engine will not cool properly if the clutch is not locking enough as the engine gets hot....
Radiator keeps blowing coolant back into holding tank
Hi, thanks for writing in. This is a sign that you may need to have the radiator system burped. This is a process that is used to relieve the air in the system which can cause the coolant to overflow...
Intermittent starting issues (takes a couple of cranks to start) & throttle surge
Hi there. From the description you have provided of your vehicle's starting trouble and throttle surge, it looks like you have already tried replacing many parts on the car.Replacing parts without a diagnosis can be expensive and time consuming without...
Why is my 2007 FORD 500 accelerates when I turn the steering wheel in the Drive or Reverse unintentionally and make the car jumps
You should have the computer tested for codes and then have the steering checked to see if there is a steering or engine issue with idle since it is normal for the engine to increase the idle when it senses...
Related articles
How a Car's Cooling System Works
Have Have you ever considered the thousands of times explosions occur in your engine? If you're like most people, that thought never enters your mind. Every time a spark plug fires, the fuel and air mixture in that cylinder blows...
How a Modern Engine Works
You You turn your key in the ignition, and the engine fires up. You press the gas and the car moves forward. You take the key out and the engine turns off. That’s how your engine works, right? It's a...
How Do I Prepare My Car for Summer?
Summer's Summer's heat, dust, and stop-and-go traffic will take their tolls on your vehicle. Follow these tips to ensure optimum wellness of your car: Air Conditioning: Have your air conditioning inspected (https://www.yourmechanic.com/services/heating-ac-inspection) by a qualified technician. Newer models have cabin...
Browse other content
Cities
Services