Nissan sentra P0303 code

It keeps reading the code P0303 “cylinder 3 misfire”. All coil packs, fuel injectors, spark plugs have been replaced. The exhuast smells normal. The oil is the correct color(maple syrup color, NOT milky). It’s not blowing through coolant. Compression test came back normal. It’s not the cat converter because the exhaust doesn’t smell like rotten eggs. The car is sometimes hard to start. it hesitates/stumbles and shakes really bad. It feels like its not getting enough power.

Anyone have any advice on what’s going on or what to do next?

Have someone check the Mass Air Flow sensor. I’ve had Nissans come in with misfire codes that were caused by a dirty/defective MAF sensor.



I would measure compression on all 4 cylinders.

If #3 is considerably lower, you might need to adjust valves, or you might have worn rings.

Let us know, please

@Kslice39 you don’t need to post 3 times (or more) to ask why you have a #3 misfire.

Anyways . . .

What are your compression readings?

Dry and wet, please

All 4 pressures were the same


Nevertheless, can you post them, please?

Have you verified that #3 spark plug is actually getting spark?

Hook up a test plug to #3 plug wire and start car. Should have bright blue spark.

Have you verified that #3 injector is actually working?

I didn’t mean to post that many times. My computer froze when I hit the button, sorry.

All the compression readings were the same. I don’t remember the exact number, I did the test a week ago. We took it all apart and the plugs were dry. We tried switching packs to see if it would say #2 or #4 would misfire but it still said #3.

This site also becomes problematic at times so don’t worry about multiple posts. It’s been a bit goofy at times for me while kicking me off or freezing.

If the compression readings are good (and offhand it sounds like they are) you might consider the possibility that the fuel injector on that cylinder is not pulsing.
This could be done with a Noid light or by using a mechanic’s stethoscope or long screwdriver as a substitute to see if the injector is clicking as the engine is running.

I will try that, but I just replaced the fuel injector yesterday. Shouldn’t it be working properly if its brand new?


The PCM provides ground to the injectors. If the injector driver is faulty, that new injector has no chance.

Ok so first off I keep having P0303(cylinder3 misfire) come up. All spark plugs, coils, fuel injectors have all been replaced and its still throwing this code.
I scanned it again this morning and this is what the code reader said(sorry it’s a lot):

MIL on
02 snsr
4 ready
02 Htr

It read these in this exact order. I have a CP9125 actron OBD2 PocketScan code reader if that helps anything.
PLEASE someone help me out! I’m desperate and I’m so frustrated with this car. I’m not sure what else to do to get it running properly!

I have the same issue I have literally replaced everything. I took it into a mechanic and he checked everything out he fixed a vacuum leak I had and determined I had a bad throttle body. Which I had suspected. So I replaced the throttle body and had it reprogrammed. But it’s still running a cylinder 3 misfire code. I even did the SES reset trick which lasted for a day then the code came back.

What are your long term fuel trims?

Honestly I don’t know I don’t have a fancy enough scanner for that.

I have a 20$ bluetooth scanner, and I can read that data with Torque Lite