Hello everyone, I've searched and can't seem to find the problem\answer. Quick run down on the car. Friend of mine has an 02 that had clogged cats, and wanted to do some go fast goodies, so we did Obx headers, 3'' CBE,nwp spacers and block of plate, nwp big bore throttle body,admin tuning intake and tune. I changed the plugs while i was in there with ngk's. checked injectors(by unplugging harness), he had recently replaced all coil packs,new cam sensor, i tried the maf from my car. I have a new fuel filter but haven't installed it yet. What am i missing. any help appreciated. Thanks

 

He messed up by replacing the coil packs. If it's not broke, then don't fix it. I'm gonna guess it's some aftermarket trash. I hope he kept the originals.

 

I think he got them from Napa. and no he don't have the originals

 

P0300 is an annoying code because it typically states what you already know (theres a misfire) but doesnt tell you anything about what cylinder(s) or whats causing it. However as already stated its very likely the new coils are the problem, any brand other than OEM (hitachi) will cause misfire issues. Id start by replacing the coils (again) with OEMs if they arent already, you can get them for 35/ea on rockauto.

 

If you wanna see what cylinder is misfiring connect a timing light to the coilpack wiring harness of that particular cylinder and if it's missing you'll see it misfire via the strobe light...It's easy and it works on these coilpack technology engines

 

We preach stay away from Autozone, O'Rielly, Advanced Auto, Napa, sensors, coilpack etc....But we constantly have org members purchasing this crap and wondering why they have all these codes....I would advice to use these store for emergency scenarios only and once you're now mobile get your permanent part on order ASAP....Order you sensors/coilpacks/etc from either Wholesale Nissan dealership sites like Tri-cities Nissan, Courtesy Nissan, ABC Nissan, and Rockauto....Come on guys, use those local purchase parts or good junkyard parts for backup or emergency parts so you aren't stranded or use them when stranded!!! That how I use these local part places cause a camshaft sensor I purchased from O'Rielly never made a year before it failed and that was removed, trashed and replaced with an OEM unit 5 yrs ago no issue since...Do you get it? I keep a cheap little tool bag in my trunk which contains wheel locks, good but used accessory drive belts, a sensor or two just in case I have a problem I'm not in a bind! I've never had to use anything in the 5.5th Gen but my 4th Gen tool bag did come into play with a defective coilpack!

 

I'd go to junkyard and find the lowest mileage VQ.

 

Never thought of that. I'll try that as well

 

Probably end up swapping the ones from my car and see what it does

 

So I have all new Hitachi coils,changed the ignition condenser, and I still have the random misfire. What's next???

 

Somehow, I am not surprised .....
The FSM (pg. EC-384) tells us that P0300 may be caused by:

• Improper spark plug
• Insufficient compression
• Incorrect fuel pressure
• EGR volume control valve
• The injector circuit is open or shorted
• Injectors
• Intake air leak
• The ignition secondary circuit is open or shorted
• Lack of fuel
• Drive plate or flywheel
• Front heated oxygen sensor

It would help if you could describe your symptoms (clearly & accurately), and see how they match with above.
I would focus on intake leaks, fuel delivery, and front O2 sensors (when changed, if ever?).

 

Possible intake leak...Hey did you install dielectric grease inside the boot of each coilpack during assembly? I would do that it's a good insulator...What do your spark plugs look like? Are they new as well? Are all the cylinders misfiring? Did you use the timing light to find the misfiring cylinder?

 

Plugs are new, and no i didn't use the timing light. Haven't gotten my hands on a timing light to try that trick. i sprayed the all around the intake and didn't detect any leaks.

 

Is it actually misfiring or just throwing the code?

plugs/compression is next
Did you check to make sure they aren't fouling?

That sucks, I was sure it was coil packs.

 

Its misfiring. I was going to do a compression test last night but couldn't find my gauge.

 

So I did a compression test last night all of the cylinders are in between 175 and 180 psi. The front 3 cylinders seems like the ignition is weak,compared to the back 3 when I disconnect the coils. The change is much more noticeable. Also the misfire is intermittent. Also after I rev it, once the revs comes down it stalls for a sec and then the misfire starts.

 

you are describing my problem, I replaced 3 coils yo try to find my problem, no luck. Ended up testing the connectors and there was the problem. One of the connectors was bad, so far 2 months and no problems..... Hope this helps...

 

I had the same issue after purchasing my Maxima, random misfire. Turned out to be a bad conector on one of the rear coils. Replaced a year ago no further issues.

 

Was it the connector or a wire?

 

It was the connector pin inside connector that was corroded away.

 

You can always put some dielectric grease if it continues, replace the connectors..

 

im going to double check them tomorrow
gotcha

 

1. Or a connector pin that's been damaged from probing the front of the connector instead of the rear...
2. I again would suggest you view your Coil packs operate using an ole' school timing light watching it missing real time...This cuts down on all the guess work...usually the missing it's even picked up by the ECU unless it's really bad....
3. Please inspect your Coil pack boots for cracks and make sure you reinstall them with dielectric grease in the boots recess for the spark plugs...
4. Please once you discover/reveal which cylinder is misfiring swapping coil packs and/or spark plugs should indicate which units are the culprit...
5. Hansen, Hitachi or NGK coilpacks are your only options...don't know how much times people must say to not equip your cars with nothing but Hansen, Hitachi coilpacks..I'll be trying the NGK units soon they're a little more expensive on rock auto but still cheaper than the $136 Courtesy Nissan online prices...But anyway...Good luck

 

Most of the time from what I've learned about po300 which I recently got is that there is more than one cylinder misfiring. Recently in my case I kept getting the code , I did the coil test by unplugging each one but .That didn't really help. So I pulled the rear bank coils and number 3;5 had oil on them. So I got another valve cover from a 6 gen car. A week later it's still misfiring so I pulled the front bank coils and they have oil as well. Replaced the valve cover and coils and now the code is gone.

 

What I don't understand is the half *** work ethic some people do...Why would you change one valve cover and not both at the same time? If it were a front bearing issue on one side! Why wouldn't you do both? If one worn out then the other is not to far behind it! Now The real question is whether you inspected any of your spark plugs during this operation?

 

Well if the valve covers have been replaced already previously with 6th gen ones that are said to not go bad like the 5th gen valve covers do, then there would be no need to replace both if everyone is saying here that 6th gen valve cover spark plug tube seals dont leak. But to my surprise spark plug tube seals were leaking on both banks with the upgraded valve cover design, and yes spark plugs were replaced as they were coated in oil, at least the ones that had the tube seal leak.

 

What does this mean?

 

The pin is either bent or pushed out of position to the point where it no longer makes contact. If youre probing around without being careful it can be pretty easy to do since the metal is very thin and pliable.

 

Tomorrow I'm going to check the ohms on the injectors to see what those readings are.