Fault code P0300 & P0303

[psychochops78]

Good morning all. I'm new to this forum and I'm looking for some help if possible. My check engine light is on and when I hook the code reader up it comes back with P0300 and P0303. P0300 isn't always shown but P0303 is consistant. I've changed spark plugs and put in accel super coils on it. Getting ready to pull fuel injectors and check them as well. Hoping this isn't a compression issue. But if it was a low compression issue, would't it run like crap all the time? Sometimes it runs like a bat out of hell. Other times it runs like poo. When it is acting up, it's usually in 1st or 2nd gear when I'm in the low RPM range and I get on it. It bogs down and shudders pretty bad. Other times is when I'm in 4th or 5th in the 3000-4000 RPM range and start to accelerate, I feel it hesitate and that's when the check engine light starts to flash. Does anyone have any thoughts on this or can point me in the right direction? It's been a great little car and I don't want to let it go but then again it does have 275000+ miles on it and I'm the original owner of it. Any help would be greatly appreciated.

[castles]

P0300 - Cylinder Misfire Detected Random Cylinders

Possible causes
Faulty spark plug (s)
Faulty ignition coil (s)
Clogged or faulty fuel injector (s)
Intake air leak Fuel injectors harness is open or shorted
Fuel Injectors circuit poor electrical connection
Ignition coils harness is open or shorted
Ignition coils circuit poor electrical connection
Insufficient cylinders compression
Incorrect fuel pressure

Tech notes
The P0300 code means that a cylinder(s) is misfiring or is randomly misfiring. Start by checking for intake leaks, intake gaskets are common caused of multi-cylinder misfiring. If no leak are found the next step is to replace the spark plugs. If the problem persists more tests needs to be done to diagnose problem, see "Possible Causes"

When is the code detected?
The control module monitors the crankshaft speed and has detected a misfire condition

Possible symptoms
Engine Light ON (or Service Engine Soon Warning Light) Lack/loss of power Hard start Engine hesitation P0300 Description When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the Crankshaft Position (CKP) sensor signal to vary, the Engine Control Module (ECM) can determine that a misfire is occurring.

Read more: https://www.engine-codes.com/p0300.html

[castles]

P0303 - Cylinder 3 Misfire Detected

Possible causes
Faulty spark plug 3
Clogged or faulty fuel injector 3
Faulty ignition coil 3
Fuel injector 3 harness is open or shorted
Fuel injector 3 circuit poor electrical connection
Ignition coil 3 harness is open or shorted
Ignition coil 3 circuit poor electrical connection
Insufficient cylinder 3 compression
Incorrect fuel pressure Intake air leak

Tech notes
The P0303 code means that the cylinder 3 is misfiring or is randomly misfiring. Start by checking for intake leaks and if no leaks are found the next step is to replace the spark plugs on cylinder 3. If the problem persists more tests needs to be done to diagnose problem, see "Possible Causes"

When is the code detected?
Engine Cylinder 3 is Misfiring.

Possible symptoms
Engine Light ON (or Service Engine Soon Warning Light) Lack/loss of power Hard start Engine hesitation P0303 Description When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the Crankshaft Position (CKP) sensor signal to vary, the Engine Control Module (ECM) can determine that a misfire is occurring.

Read more: https://www.engine-codes.com/p0303.html

[Xenyd]

Did you get this fix?, I have the same problem with my Yaris 2007. It has 260000 on the odometer. I changed the ignition coil and spark plug already and yet it is still acting up. It's really weird

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[bizzlebaby]

Did either of you ever get this fixed?