Need help p0300, but runs like a champ 

[stuner494]

About 2 weeks ago I purchased a 2002 spec-v with 89,000 on it knowing the check engine light was on. After taking it to AutoZone I pulled up 3 codes p0301, p0300, and p0420. First thing I did was clean the cai filter that was way past due. Next i cleaned the intake tubes, MAS, throttle body, and upper intake with them off the car. After everything was put back on I rest the codes, and 100 miles later pulled up codes p0300, p0420, and p0507. So I did the relean which got rid of the p0507. Trying to find why the codes p0300 and p0420 where pulling up on the car I checked the forums and came across the butterfly screw and cat problem. So i put Loctite on the screws and gutted the cat, then put a ghetto slim on the lower 02 sensor. Rest the codes and only pulled up a p0300 which I can’t figure out why it coming up. The car is now running like a champ with no stumbles or misfires. The only issue it has is when I do a warm start the motor will swing sometimes for maybe 2- 3 seconds before starting other times it’ll fire right up. After having about 2-3 warm hard starts in a row the car will throw a p0300. I’ve changed the spark plugs to NGK’s from bocsh (which all came out by hand), checked for air leaks (none), changed the cam and crank sensor, watched the coolant which has not moved, and torqued down the upper intake 10 foot pound then again 20 pound starting from the middle to the ends. staring to think it a fuel problem but I’m not sure. Any ideas on what could be causing the p0300?

Update: I was driving down the freeway and all of a sudden the cel went off for some reason, but when I turned off the freeway to a stoplight the car started to go up and down with the rpms. It did this for a 2 days in tell the CEL came back on which fixed the cars idling problem

Check engine light off= car stumbling on idle
Check engine light on= car running perfect

Anyone have a idea what could be causing this?

[B15pwr]

Check your fuel pump?


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[i68k]

hopefully youre not suffering motor damage from the p0420. as a bad headgasket or loss of compression can result in a misfire. also, its possible you had a p0300 and another p0300 pending, youd need to delete all of them. p0300 is just a random/multiple misfire. have you checked your oil and coolant levels?

if you pulled the maf and tb, you may need to do ALL 3 relearns, not just the idle relearn. hopefully you cleaned the maf and tb using only 'cnc maf cleaner', so you dont ruin the sensors inside of them. harsh chemicals will ruin the sensors on contact, such as carb cleaner. you should be doing these in order:
1. accel pedal released learning
2. throttle plate closed learning
---warm up motor to operating temp
3. idle air volume relearning

its possible you could have a failing coilpack, which usually just misfires for 2-3 seconds on cold startup. normally, you can just rebuild the coilpacks if the springs are loose or the capacitor is bad.

fuel issue is a probability, do you prime your fuel? can you hear the pump priming? do you smell gas? you would need to t the line to check your fuel pressure. most fuel issues are related to starting the motor after it was just running.

[stuner494]

the coolant level never moves and the oil level is good. also when i cleaned the MAF i did use the CNC cleaner. do you have any links to where i can find out more on the 3 learning step as i only did number the third one you mentioned?

[i68k]

the exact relearns and specs are in the fsm
here's a link for the quick relearns:
http://www.b15u.com/sentra-specific-...e-relearn.html

you can download the fsm around here for free as well
the relearns are in the fsm. try these:
nicoclub.com/fsm
allsentra.com/fsm

you coolant level should move slightly, but your coolant shouldnt disappear rapidly. the level should chanage when the car is cold/hot, and water evaporates as well. so when your motor is cold, the level should be slightly lower than when the motor is hot. regardless, keep and eye on the level, disappearing coolant is a sign of leak, or bad headgasket. hopefully your coolant is circulating, and shows on your temp gauge.

EDIT: can you define your definition of 'warm hard start'. also check your battery voltage, motor on&off. make sure your battery terminals are tight, and has good ground contact.

[stuner494]

warm hard start= when the car swings for longer than normal on start up after it's seen full temp.

but yeah the coolant level is good with no steam from the tail pipe. also i did a check for coolant on the pistons when i changed to NGK's with all 4 pistons being black.

i've never heard the fuel pump priming on start up, but it sounds like the fuel pump is priming all the time with a ringing sound that never goes away.

thanks for the links

[i68k]

you mean when youve just turned the motor off, it doesnt turn back on, but it keeps turning over without starting? you need to prime the fuel.

1. keyOFF for 10 seconds, in neutral
2. keySTART for 2-3 seconds, hear ringing?
3. press clutch pedal to start motor.


when your motor is off, you put the key to keySTART. you should hear a ringing, wait 2-3 seconds. then, while keySTART, press the clutch pedal to start the motor. did you hear the ringing before the motor started?

if you hear ringing afterwards, it could be bad ground connections anywhere, or bad charging system/battery. it also could be a simple pulley or something, does it ever go away while driving? assuming its not your radio....

[stuner494]

no the ringing never goes away

[i68k]

if youre priming, and it works almost all of the times, you just need to add a check valve to the fuel line, and you can fix this immediate pressure loss.

as for your ringing, can you identify what part its coming from? does it get louder when you press the throttle? checked your battery terminals for tightness, and good ground contact? check your voltage motor on&off. have you checked to see if it is your radio? maybe power off the radio, as dead sound can be sent to speakers, even when volume is on 0. does the ringing start before or after you put the key in, or start the motor? did you check all the other grounding locations?

[stuner494]

the ringing only happens with the motor running. the car always primes when its cold but if it's at running temp then shut off and turn on after 5 mins there is no priming. is there any more info on adding a check valve? cuz im having a hard time finding anything about it

thanks for the help i68K

[i68k]

no, no.

if its at running temp, then shut off, you will NEED to prime your fuel. meaning if you just turned off your motor, you need to prime your fuel, before starting the motor. see post #7 above. thats how you prime your fuel, this is what returns pressure to the fuel line, so the motor will startup right away. you can always prime the fuel, but if priming works almost all the time, you can just add a check valve to the fuel line.

check valve method, you can add the check valve on top of the fuel pump assembly, so it holds more line with pressure:

http://www.b15u.com/sentra-specific-installation-guides-technical-info/12861-how-fix-hard-starting-about-$20.html

[stuner494]

ok thanks for the help i68k. with the releans and a replacement pvc valve i was able to pass smog. the 2 seconds on 10 second off works great for the fuel issue, but eventually i will put in a check valve. thanks again!!!!!!!!!!!!!!

[i68k]

anytime. im not sure the specifics of the check valve, i always prime my fuel. you may not have to wait the full 10 seconds with keyoff, i usually go by the sound of the relays. when you turn the key off after being on, you can hear a couple of clicks coming from the passeneger floor area. once those relays switch, i usually hear 2 clicks, you can go ahead and start priming with keySTART. i usually only wait around 4-5 seconds listening for the clicks, just so youre not sitting there forever to restart the motor, now that you know what the problem is, it is a very common problem, and priming seems to be a fairly reliable fix, even though it involves some trickery.

[stuner494]

yeah ive got the priming down now