I keep getting a cylinder 3 misfire code P0303. I have replaced the spark plugs and ignition coils and have had no luck.
I have had a cylinder 3 misfire code a few times and I have addressed the issue they way I was told to. Change plugs and coil but nothing seems to work. I have had a compression test done and all heads on the car are fine within 2 percent of one another. I don't smell any gas and the car does not shake. I don't believe I have any leaks as I check regularly. What else could be wrong?
My car has 66342 miles.
My car has an automatic transmission.
Experienced mechanics share their insights in answering this question :
Hello There,
You may want to try checking things like mass air flow sensor, fuel pressure, injector connections/pulses, etc. Often times, when these components are not working properly or causing a lean fuel condition, this may cause a misfire due to the lack of enough fuel to properly ignite the air/fuel charge in the cylinder. You may also want to check for air or intake leaks as this can also contribute to a lean fuel condition that may potentially cause a misfire, although not quite as likely as the others mentioned.
How to Identify and Fix Common car Problems ?
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The P0303 code means that your Powertrain Control Module (PCM) or Engine Control Module (ECM) has detected multiple misfires on cylinder number 3. The misfire monitor tracks crankshaft speed variations through the crankshaft position sensor (crankshaft sensor).
You might get a misfire code after spark plug replacement for an individual cylinder like a P0303. The code indicates a misfire in cylinder three. Sometimes the spark plug is dropped, and the ground electrode and the center electrode can make contact. Or the problem could be with the connection to the coil.
For example, the issue can stem from a faulty spark plug or wire, which in the grand scheme of things is relatively easy to repair. However, the error code may also occur because of a faulty catalytic converter or defective computer system, which can vary in expense.
Yes. While the damage may seem small initially, the longer you drive with a bad oxygen sensor, the worse the damage will become. Eventually, you may experience rough idling, poor acceleration, engine misfires, an illuminated check engine light, and failed emission tests.
The most common causes of misfires are worn, improperly installed, and mishandled spark plugs, malfunctioning ignition coils, carbon tracking, faulty spark plug wires and vacuum leaks.
An engine misfire can be caused by bad spark plugs or imbalanced air/fuel mixture. Driving with a misfire isn`t safe and can damage your engine.
The most common causes of misfires are worn, improperly installed, and mishandled spark plugs, malfunctioning ignition coils, carbon tracking, faulty spark plug wires and vacuum leaks.
A leaky head gasket will usually cause multiple cylinders to misfire, especially ones next to each other. If you move a few spark plugs around and the issue stays localized within certain cylinders instead of localized to problematic spark plugs, you should check your head gasket.
Engine misfires happen when one of the cylinders does not produce sufficient spark or compression and lack of fuel. It could involve more than one cylinder. It can be caused by a faulty spark plug, fuel injector, ignition coil and or worn cylinder.
A leaky head gasket will usually cause multiple cylinders to misfire, especially ones next to each other. If you move a few spark plugs around and the issue stays localized within certain cylinders instead of localized to problematic spark plugs, you should check your head gasket.
Relevant Questions and Answers :
the most relevant questions and answers related to your specific issue
I keep getting a cylinder 3 misfire code P0303. I have replaced the spark plugs and ignition coils and have had no luck.
ANSWER : Hello There,
You may want to try checking things like mass air flow sensor, fuel pressure, injector connections/pulses, etc. Often times, when these components are not working properly or causing a lean fuel condition, this may cause a misfire due to the lack of enough fuel to properly ignite the air/fuel charge in the cylinder. You may also want to check for air or intake leaks as this can also contribute to a lean fuel condition that may potentially cause a misfire, although not quite as likely as the others mentioned.
One month ago cel came on I changed spark plugs to after market plugs. One month later cel on again with misfire code.
ANSWER : If the spark plugs hadn’t been changed until 130k, it was time for the to be replaced anyway. This is probably why the dealer went with that repair as worn spark plugs can cause misfires. Ignition coils are another part that may fail and cause misfires when they malfunction. A compression test and cylinder leak-down test will show if there is a problem with the valves. You can try having the coils replaced and the valves adjusted by the dealer. Consider hiring an experienced technician like one from YourMechanic who can come out and conduct the same tests as the dealer could and determine the cause for your check engine light.
Engine light fault. There was a bad spark plug and a failed ignition coil. Replaced both the coil pack or spark plug.
ANSWER : Hi there. If the light is coming on then shutting off and returning on, then if the issue is for the same coil, there could be an issue with the wiring on the coil plug. Check the wiring on the coil plug and see if the wires are split, broken, or burned. If there is nothing wrong with the plug, then the main engine harness has an issue / short and may need replaced. If you need further assistance with your ignition system, then seek out a professional, such as one from Your Mechanic, to help you.
Getting to cylinder #3 to replace ignition coil?
ANSWER : I could go into a long drawn out direction to remove the coils on the engine but if you go on google and put in "2002 Infiniti q45 #3 coil removal" in the search bar you will see many good articles and videos showing the removal and replacement of the coils and spark plugs for your car.
Yes, you should change all of the spark plugs when you put in the new coils. Make sure you do all of this when the engine is absolutely cold. This should help you in removing the coils and plugs, and installing the new set of spark plugs free from damage to the threads in the heads. If you need assistance with getting this done, reach out to a certified mechanic who can replace your spark plugs and coils at your convenience.
Spark plug chaos. Rubber stoppers are preventing the spark plugs from coming out.
ANSWER : Hi there. Try using a pair of small needle nose pliers to pull off the rubber boots from the spark plugs. As you pull, twist the rubber boots to break them free. If you cannot get the rubber boots off, then try using some mineral oil on the boots to aid them off, then clean off the oil with soap and water with degreaser. If you need further assistance with removing the boots from the spark plugs, then seek out a professional, such as one from Your Mechanic, to help you.
What repairs fix codes P0172 and P0304? I just had all the spark plugs replaced recently.
ANSWER : The P0304 code indicates a misfire has been detected on cylinder 4. The P0172 code indicates that the fuel mixture is richer than the mixture control can compensate for. It’s possible that they are related, but not necessarily. Rich mixture can be caused by excessive fuel pressure, or sometimes by leakage at a fuel injector. If your misfire is caused by leakage at injector number four, then it’s likely that the two codes have a common cause. It’s also possible that you have had a spark plug foul because of a rich mixture. Again, that would be a common cause. But it is also possible that you have a failure in the number four ignition coil, they are not uncommon. In that case, the P0172 would be a separate issue altogether. If I were working on the car, I would try to determine the cause of the over rich mixture and then work from there. In any case, you need to have a qualified technician check this thing out. Contact Your Mechanic and they can send a technician to your home or office to check out your car and tell you what needs to be done.
Misfiring Cylinder after replacing the plugs three months ago. Is it a chance that the whole batch of plugs may have been defective?
ANSWER : Hi there. The best thing to do is switch the coil over from cylinder 3 to cylinder 1 and see if the misfire continues with cylinder 3 or if it changes to cylinder 1. If the misfire stays with cylinder 3, then either the spark plug or spark plug wire has failed. Or there could be an issue with the cylinder not sealing or getting fuel. If the misfire changes to cylinder 1, then the coil pack is not working. If you need assistance with diagnosing your misfire, then I recommend seeking out a professional, such as one from Your Mechanic, to help you
After part replacements, spark plugs do not work – 1996 Lexus LX450
ANSWER : If you have a Check Engine Light on, first check for those codes to determine what engine management thinks is going on. If no trouble code, check the ignition fuse behind the driver side kick panel (carpeted panel at foot level on the left – for left-hand drive vehicles). If the engine is spinning quickly, and doesn’t appear to be meeting any resistance (as a motor with good compression would have), you may have a broken timing belt. If so – STOP, call a professional mechanic, like a certified technician from YourMechanic for help.
