everyone's nightmare.. p0300 code. =( after engine swap.
 

after they install the new engine just to my luck. p0300 code. have to hurry up and fix it before Friday if not im gonna have to cancel my appointment for the tune.

here's what I already checked=
intake leak.
spark plugs and coils. To make sure they were all firing, took out one by one and threat them out at night. All 6 of them where working.
next I checked coils plug with the help of the service manual, all 6 were right.

next step: change my injectors.

MAf air flow sensor: I had an extra one but as soon as I changed it I got the code p0103 witch means bad air flow sensor. so I connected my other one back on and the code disappear but still have p0300.

Did you check this link?

http://nissanhelp.com/diy/obd_codes/p0300.html

no. but the service manual tells you all that. thanks.

Have you noticed anything else? Or just the code?

so far it's just the code. the car doesn't turn off or anything like that. and some times after driving it for a little the check engine will disappear buy as soon I hit a stop will come out again.

So you haven't noticed any misfires?
If not, just a pure guess, cam sensor?

nop, that's what I'm hoping for that it can give me a code so I can know witch cylinder is it. I hardly think it's a cam sensor since it's my old ones and the engine was running good before beside if it was the cam sensor it would give me the code. but I have extra pair of cam sensors I'm gonna replace them just to see.I also had my cams upgraded to tomei but I doubt it's the timing since it's not giving me a code related to that. and if it was timing the car would even turn off or run bad and my car runs smooth. I cleaned my Air flow sensor right now and unplugged the battery to reset the ecu came for a 10 minute drive and no codes until now.

no luck,
thins I already did:
checked vacum leak.
replaced spark plugs.
I have extra set of coils so I replaced them.
check every single spark and coil make sure it was spark on it.
replaced cam sensors.
replaced MAF air flow sensor.
cleaned all 4 oxygen sensors. Tomorrow I should check voltage on all 4 oxygen sensors.
don't know what else is missing.
the weird thing is that when I'm driving tha car the code doesn't come out only when it's park and I set the rpms to 3 thousand.
can it be because of my tomei cams (not being tune)? rough idle and makes the crankshaft sensor think wrong?
I am gonna take the it to get tune but I want to make sure everything is working before I take it. thanks in advance for the help.

Skip the tune. Go back to school, and learn how to write clearly.

sure as being my 3rd language not bad at all right? beside I was on my phone, as you know sometimes it changes words. it's ok though haters gonna hate.

Well it sounds like it's not electrical then, unless you replaced a bad sensor with another bad sensor (happens sometimes). Might as well do a compression test since it's super easy. If you took the spark plugs out already, I'm sure you can do it yourself for cheaper than a shop.

Maybe the tune is off too though. If your tuner goofed, he could have you running too rich at some points which will cause misfires that are intermittent, random and hard to detect unless you're really in tune with your cars throttle response.

I knew my base tune was off, and could feel the misfires between 2-3k RPM. Sure enough it eventually through a SES code at me, didn't even have to read it, knew it was the tune. Got it dyno tuned and no more misfires.

Who did your tune? Was this on a dyno or street? Wideband installed for tune to monitor AFR?

You are the most consistently arrogant and inconsiderate person on this forum, and anyone who has seen 10 posts here knows what that implies. Why not just help people instead of taking the equivalent amount of time to post useless and insulting posts? Or even *gasp* hold your tongue?

the sensors I replaced with were brand new. It hasn't been tune yet, my appointment it's on Friday and church automotive is going to do it. But yeah after doing some more research I think it is because of my cams (272s) and the old tune just doesn't add up it's tuning way to rich I can tell by the spark plug. I'm going to make the compression test today. thanks.

here's a quick video, I took the car for a 30 minute drive around the city and never had p0300 light coming out. as you can see the idle is not that bad for 272 cams without tune.

I doubt it's your crank sensor, every time I've had one go bad I couldn't get an engine to rev past 2000rpm.

I was thinking cam sensor because a bad sensor could incorrectly indicate a misfire (long shot, but was worth a try).

Did you read the link I posted? Fuel pressure and compression are still areas that should be checked.

:+1:

I am going to work on those 2 today.
thanks Syner.

Good luck, and post back if you find the issue.

compression test done.
all cylinders where with in 190-180.
after doing some more research and talking to some members that had cams installed, they said it should be expected since I haven't got a tune. I really think that is the reason since I drove the car today freeway/city for 1hour+ and code didn't came out.

Tune or fried ECU.

don't really see how my ecu would be fried since it hasn't been touch. I'm still going to check it put tomorrow morning. thanks.