What is the main problem for p0300 on 02 Altima 2.5


Asked by Aug 09, 2015 at 02:45 AM about the 2002 Nissan Altima 2.5

Question type: Maintenance & Repair

I put new spark plugs in last month
change two out of four coil packs an
car is worst than before hesitate in
drive with foot on brake blinking
engine over a certain speed I need to
know what is the main problem

25 Answers


Have the catalytic converter checked

1 of 1 people found this helpful.

I changed the cat 2 months ago


Do you think it's the 02 sensors? Maybe


Usually when the check engine light is blinking that a sign of the catalytic converter so I would have the code read with a scanner to see exactly what the problem is.


Yea code came back as p0300 multiple misfire

2 of 2 people found this helpful.

Hi nice to meet you. The p0300 is a DTC for multiple missfire. You say you change the sparkplug and two coils, and check the catalitic converter. Ok. You need to verify the knock sensor, the cam sensor, the flow meter, and map sensor. You need to scan the car and take fuel pressure maybe you have poor fuel pressure.

1 of 1 people found this helpful.

Nice to meet you 2 I change cat but I didn't put new 02 sensors in you think that might be it

1 of 1 people found this helpful.

The o2 sensor or EGO sensor don't cause a PO300. If you have this kind of dtc the pcm is trying to say all cilinder are not firing good. You need to find the reason for all cilinder missfiring. The cat can do this problem but you are readi change. The other thing can do this is a bad knock sensor or a poor fuel pressure.


Verify you don't have a bad air leak in the multiple or air induction system. A broken air house etc.


Ok Ima check it out is there any thing I can do to fix till next week? Until I fix if


Can I try motor treatment?


Maybe. But you need to scan your car again. I think you have fuel pressure problem. You can fill the gas tank in a half with gasolin obvius and add an half of 1qt of transmission fluid IN THE FUEL TANK. The transmission fluid have cleanin properties and don't damage your fuel injectors and rise your fuel octane dont't damage. If don't help don't damage. Don't worry. But i still think you have fuel pressure problem or maybe with knok sensor, cam, or pcm. Thath wy you need to scan.


Ok thanks I been seeing stuff about seafoam

Check your firing order make sure you didn't wire it back up wrong after changing plugs have you looked at your dstributor cap and rotor button if not i would but for real dude it sounds like you put the wires on the plugs wronge after u changed the plugs and wires and if u used the old wires you may have riped the metal tab that connects the plug to the wire and they might be bad signal inside the boot change wires and make sure order is rite

You can't put the firing order back incorrectly. They're essential coil over plug, no wires except the ones that plug into the coils for power. I currently have the same issue and I'm torn between it possibly being 3 things: 1) Bad ignition coils 2) Bad fuel injectors 3) Bad intake gaskets I'm intent on replacing everything with new within the next few days. If it doesn't fix it, I'll be removing the head and inspecting it for cracks. The gasket doesn't appear to be leaking, as I'm not losing coolant. The head may be cracked, which I'm assuming is unlikely because the car was running perfectly before this started. I moved my coil packs around in an attempt to pinpoint what's going on, but it's saying it's a random misfire every time now. As for the cat - The precat has already been replaced, so I highly doubt this is an issue at all, nor would I suspect it created a misfire even if it weren't replaced.

I have a 2006 Nissan Altima 2.5 and had a corroded positive battery terminal which caused my check engine light to come on. Got the code read and it came up with p300. Replaced the terminal end with new one. Check engine light went off and car performance greatly improved.

I have a Nissan Altima 06 2.5S. My car hasn't been 100% since I bought it used. At one point it didn't want to turn over so a mechanic said I needed to change the MAF and Crankshaft Postion Sensors. It has about 3 months since and it worked well. But now from one day to another my car just started sputtering and jerking. I also noticed a huge loss of power in acceleration. I don't want to get charged for the wrong thing again. I sparked Carb cleaner all over and didn't find any leaks. I have heard people mention changing the sensors that have already been replaced but at this point I'm sure it's a sensor because I don't see any structural failures. I have an AMP that the the previous owner installed, and I'm not sure if it's draining too much power from the battery to go to the engine components or even sensors. I have not tried to take it out since it seemed like an irrelevant cause.

if sensors are not getting the proper pulses because not enough amps this could cause several sensors to trigger. As soon as i replaced the battery terminal i noticed the check engine light went off and performance improved.Because the battery cable had been disconnected i relearned the thottle body to eliminate the rough idle.

Update: I had a blown head gasket, I am going to a mechanic to get an estimate.

Jose how did you come to the conclusion that it was a blown head gasket? My 05 Altima is shutting off. At idle the car runs horrible once I accelerate it runs fine. I did change out a bad coil, new spark plugs, new crankshaft sensor, checked the vvt solenoid , checked timing chain , checked fuel pressure, and also did a compression test. Everything is new or checked out to be fine but still shuts off at idle. The only cel code I got was p0300. No other codes .

Ivy91, Before anything, Try switching/cleaning the MAF sensor as well ! I ended up having a blown head gasket but i didn't notice until I my car jerked everytime I accelerated. If you want to make sure if you have a blown gasket do the following: 1) fill the radiator full with water and leave the cap off and have someone else turn the car on, if water jumps out of the radiator then that means the pressure from one or more of the cylinders are exiting through the cooling system. 2) take out all spark plugs and check to see if there is water in any of the cylinders w/ a flash light. 3) check the inside of the oil cap for white residue, that's an indication of oil mixed with water or coolant (this one isn't as good bc it happens to anyone) Aside from that my car is running good now but the p0300 is still showing up and it's really annoying. I think altimas from 2000-2006 got recalls on this code.

Jose we did that as well there was some fluid coming out of the radiator cap not too much. And I'm threw a camera in each cylinder they were all good that's why I am not sure if it will be a head gasket. Oil is coming out clean no coolant in it.

Other problems for random misfire is injectors and if you have a vacuum leak. These two are very hard to fix on your own, thus expensive when given to a mechanic. There are different home tests you can do but look online because they're hard to explain

Cleaning the throttle body also helps rough idle. I did that myself. You just need a few wrenches and carb cleaner. There are videos online. Let me know if you find the problem!!

Yea my buddy is a mechanic we've done it all. I do all the work he just tells me what to check for. He will throw the scanner on and all cylinders run fine.

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