My 2003 350Z has been showing CEL P300. The car hesitates sometimes and when running the CEL light blicks for a while then its just on then it goes back to blinking. As you sit inside the car everthing shakes when idle. I just replaced the spark plugs and it keeps doing it, what else can I check or do i have to take it to dealer and if i do does the warranty cove it?? PLease help.

 

moved to correct section

 

Mass air flow sensor, vaccum leak, fuel supply, compression... Most likely one of the first two and I have a spare mass air flow I'll sell you if you need it

And the blinkin is the worst Cel to get, needs attendin to quick or it'll cause damage to the cats or motor

 

How many miles and how steady is your idel? And yea warranty should cover it...

 

P0300. Random cylinder misfires IIRC...


MAF sensor, spark plug gap, coil packs, bad gas, clogged injectors.


If it was a vacuum line, you'd hear a loud hissing sound.

 

yes.

partial yes.

random mis-fires are usually cause by bad plugs. just cause you put new ones in doesn't mean they're good or correct ones. make sure you're running denso or NGK premium platinum. is the plugs are correct and new, it unfortunately might be a computer issue. normally randoms are caused by bad plugs, wires arcing or loose connections, bad distributor cap/rotor or ignition coils, or the ignition control module. since the vq35de has coil on plug ignition, out of the aforementioned it has only the plugs. the computer send the signal for spark to the coils in the place of a control module on this engine. it might have something to do with the injectors either being clogged or not working properly (i.e. not getting a good signal from the computer) also. the problems you are having are normally from multiple codes, not just a random mis-fire. go to a local auto parts store and have them scan it for codes again to check for anything else. after that, depending on the results, if the CEL is in a constant flashing state, i'd take it to a dealer or trusted nissan mechanic asap. GL

 

It's rare for a p0300 code to be caused by plugs or coils, yes both of those will cause misfires but usually one at a time, so usually you would have a speific cyclinder misfire code.... Like p0304 for cyclinder 4.... And another thing you can't always hear vaccum leaks so you won't always hear your hissing sound...

Still most likely cause is mass air flow, or vaccum that would be the first things to check than check your fuel system, injectors or pump or your motors compression... Further list of things would be o2 sensors, crank angle sensor than yes plugs or coils cause there is the possibilty but it's just not as likely

 

My 2003 has 46000 miles and the spark plugs I just put were Ngk Laser Premium , I guess I will take it to the dealer but i've heard alot of people say that most dealers are no help and dont fix the problems.

 

I took it to the dealer and they found out it was ignition coil number 6 that was misfiring. And they also changed the throttle body sensor since it was giving me that code also. The CEL turned off and has been off , now the car runs smooth again, but it costs me close to 600 dollars. Well it doesnt matter as long as the Z runs great. Thanx for the replys