What repairs fix codes P0172 and P0304? I just had all the spark plugs replaced recently.
My check engine light has been on for about a month now. The vehicle seems to stall and feels like the engine loses energy sometimes or wanting to come to a stop. I had the check engine light checked and got codes P0172 and P0304 and was told to replace ignition coil for cylinder 4 and that spark plug. I just had all four spark plugs changed so is it necessary to replace that one as well? And should i replace all the ignition coils or just that one? Also what codes fix this if not the ignition coils?
My car has 150000 miles.
My car has an automatic transmission.
Experienced mechanics share their insights in answering this question :
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.
How to Identify and Fix Common car Problems ?
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The meaning of fault code P0172
P0172 means that the air-fuel mixture is too rich for the engine to run effectively, containing too much fuel or too little air.
A P0172 may also happen due to a misfire. In such cases, you may also inspect some of the other important details. Exhaust – look for probable leaks in your exhaust, especially between the oxygen sensor and the cylinder head. Exhaust pressure pulses can create a partial vacuum, allowing air to pass through.
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.
Faulty Air-Fuel Sensor or Oxygen Sensor
If this sensor is faulty (or the Oxygen sensor in some cars), it`s likely that the check engine light will be triggered by the P0172 code or a similar one.
Error code P0172 is an OBD-II diagnostic trouble code (DTC) defined as “System Too Rich (Bank 1).” The P0172 error code is set when your Engine Control Module (ECM), also known as Engine Control Unit, detects too much gasoline in the exhaust gas coming out of your combustion chamber.
Common Reason: Code P0172 is often related to a vacuum leak.
When a misfire code is seen it is telling us that the cylinder is not firing as it is supposed too. This means the engine runs erratically on that one cylinder or not at all. The engine tries to compensate for this cylinder not firing and can cause the engine to run rich, or lean.
Check Mass Air Flow sensor: Remove the MAF sensor and look for signs of contamination. Debris that makes it past the air filter or oil from an aftermarket air filter can stick on MAF sensor and cause inaccurate signals. If dirty, clean the sensor using a quality MAF cleaner.
As mentioned, running rich is the result of a faulty combustion process, and this leftover fuel escapes into the exhaust in all of its stinky, polluted glory. Usually, our catalytic converters prevent the smell from appearing.
A bad O2 sensor should not affect engine starting, cause a misfire (unless the spark plugs become carbon fouled), or cause engine stalling or hesitation problems. A sluggish or fouled O2 sensor will typically read low (lean) and cause the engine to run rich.
The reading is too lean (i.e. too much air or not enough fuel). P0171 is a bank one reading lean, P0172 is for bank two reading lean. If the PCM is saying is that the sensor cannot be sense, that would be a different code.
Oxygen sensor failure can often be traced to one of three common factors: Age and high mileage, an internal contaminant (poisoning) or an electrical issue. One or two wire unheated oxygen sensors should be inspected or replaced every 30,000 miles.
Oxygen sensors are fairly easy to diagnose and replace. Typically, you cannot repair a faulty O2 sensor. It must be replaced because of the technology and materials in its housing.
Another cause of misfires is vacuum leaks. A leak into the intake port of a cylinder can cause a lack of fuel. Vacuum leaks on individual cylinders commonly occur around intake-port gaskets or vacuum-hose connections.
If the intake manifold vacuum is higher than normal, the base ignition timing or intake camshaft timing might be too far advanced. If the gauge fluctuates, one or more cylinders are leaking vacuum through a reciprocating part like a leaking intake or exhaust valve or burned piston.
One of the most common reasons is that you simply may have a faulty O2 sensor that needs replacing. If an O2 sensor receives too high of voltage, or experiences corrosion around the sensor connector, this can very easily damage the sensor and cause any of these codes to appear.
Disconnect both O2 sensors (front and rear). Start the engine and allow the vehicle to idle. After faults have stored: Cycle the ignition OFF/ON 2 times with a 10 second pause in between key cycles.
A clogged or failed exhaust gas recirculation or crankcase ventilation valve or faulty oxygen sensor can send the wrong signals to the computer and cause misfires.
Dirty or Old Spark Plugs
If your engine is misfiring, you may be able to fix the problem easily by replacing your spark plugs. Spark plugs are relatively easy to remove from engines and inspect for damage, and at less than $25 a piece, they are relatively cheap to replace, too.
Code indicates that the mixture in bank 1 is too rich. It can result from faulty: MAS sensor, fuel injectors, oxygen sensors, incorrect fuel pressure.
Misfire at Idle Only. Your car may drive perfectly fine but display signs of little hiccups or small misfires at idle. Generally, the cause of a misfire at idle is an incorrect air-fuel mixture. This can be caused by a faulty O2 sensor, a fuel injector that needs cleaning, or even vacuum leaks.
Check Mass Air Flow sensor: Remove the MAF sensor and look for signs of contamination. Debris that makes it past the air filter or oil from an aftermarket air filter can stick on MAF sensor and cause inaccurate signals. If dirty, clean the sensor using a quality MAF cleaner.
Relevant Questions and Answers :
the most relevant questions and answers related to your specific issue
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.
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.
Code P0304 (spark plug and COP already replaced – reset code and still have a miss on 4 cylinder.
ANSWER : If the fault is now pinned down to one cylinder, a possibility is a faulty fuel injector. Faults can be of various sorts: injector leaks, the injector driver in the ECM, the injector itself in terms of the electrical solenoid/circuit. But, there are other possibilities and all will have to be tracked down until the fault is found: Faulty oxygen sensor(s); Burned exhaust valve; Faulty catalytic converter(s); Poor compression in that cylinder; Defective computer (rare). To get this resolved, the recommended service is a misfiring diagnostic. If you request that service, the responding certified mechanic will get this diagnosed and resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic.
Engine will not stay started. I have replaced idle control valve map sensor spark plugs spark plug wires no check engine light is
ANSWER : You have a problem with the distributor assembly. I recommend replacing the distributor assembly. This will replace all the possible sensors and coil for the ignition and fix the problem you have.
Check Engine Light is on – codes P0313, P0299, P0304
ANSWER : Hi there. Based on what you’ve described, this could be a combination of faults between 2 or more things; however, I don’t believe the coils and spark plugs are at fault. One of the codes is set during a low fuel misfire (lean condition), one is specifying a misfire on cylinder 4, and one is a turbo related code; all based on a generic code investigation.
The make and model of the vehicle helps, but is not necessary at the moment. When a low fuel pressure misfire is set, there is a lean condition that has been detected by the sensors and one of the codes is telling us in which cylinder this is occurring. A possibility is a restricted fuel injector, loose injector harness, poor pin fit in the wire harness, and an air leak near that cylinder’s port in the intake manifold.
I’m leaning more towards a leak or crack somewhere creating an air leak since we also have a turbo related code stored and an intermittent rough start when cold. I strongly suggest having a qualified technician perform an inspection to determine the root cause. YourMechanic has several available technicians that can assist you with a Check Engine Light inspection and determine exactly what is giving rise to codes P0313, P0299, and P0304.
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.
I have a p0171 code on my ford ranger 2.5 and have replaced fuel filter maf sensor, iac sensor, fixed vacuum leaks, replaced fuel
ANSWER : Hello there. You might to read this article about the P0171 OBD-II trouble code; as it will give you ideas on causes and possible solutions.
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.
