zyou8er

iTrader: (1)

Hi all, I keep getting P0300, Multiple cylinder misfire. I have replaced all plugs, and swapped out coils from my brothers 350z, New Cams shaft sensors, and new Crank shaft sensor, New downstream o2 sensors and also new A/F Ratio sensors, New injectors and fuel pump, did fuel pressure test and its 51psi, so that is good. Did a vacume test at my buddies shop, and it has zero vacume leaks. Performed compression test and all banks were 180psi 185psi, so that is good.
My next suspect is the PCM/ECU, as there is nothing else that i can think of which would cause a P0300. I will check the Timing Chain Few days from now. Also, I have a new clutch and JWT Flywheel. Basically i have replaced almost everything, yet i'm still getting P0300. Any info would help. Thanks A lot!!!

woody03

iTrader: (5)

How quickly after clearing does the code come back? Any rough idling? How often do you feel or hear the miss? Mods?

zyou8er

iTrader: (1)

Hi, i don't drive it. Just by letting it idle for about 20 minutes, it gives the pending p0300, then another 10 minutes or so the MIL comes on. Also, when it is cold as the RPM's are high, you cant feel it but as soon as the car comes to operating temps, and the idle is between 630-680 you can feel the miss, and in twenty minutes of idle, the MIL comes on.

bikinilust

iTrader: (9)

Checked yours grounds and connecters for corrosion and tightness?

Was there anything done to the vehicle prior to the p0300?

Does the vehicle ping/knock?

Or have you already figured it out?

ZGOD

Did you check your spark plugs?

zyou8er

iTrader: (1)

Sorry for late reply, was super busy with work. All grounds are good, i changed them also. Used electrical cleaner on all connectors and still no help. Bikinilust, I had a blown Eng., and bough a good engine from LKQ, And when the eng. was out, i changed out the water pump. I'm thinking that the chain might have skipped a tooth, not sure. The vehicle does not Ping, honestly i have not driven it yet been super busy, i let it idle and once warmed up, you can see the misfire as the idle is rough, and it is running super rich.
ZGOD, all new plugs OEM. I went and bought another set just in case, still same thing.

PS. one thing i noticed is, the last two times while i had the car idle and was trying to figure out what is going on, i was in the car, all the sudden the car died, and it radiator fans kicked on full speed, but the car would not start back up, unless i removed the battery terminal and reset the ECU/PCM. This happened couple of times. I'm thinking that i might have a Bad PCM?

bikinilust

iTrader: (9)

Any history on the engine?

zyou8er

iTrader: (1)

Engine i bought from LKQ, It has under 24k miles, yeah i had my cousin run the vin number and it confirmed. I did perform a compression test, and all pistons were 185-190psi. I just installed a new pcm, and had a locksmith program the key, and still getting p0300.
I'm really thinking that, when i changed out the water pump, the chain might have skipped a tooth or two, so that is what i will check for next once i have a day off. If the timing chain is good, then the other thing i will look at is the flywheel, i did install a JWT flywheel when the Eng., was out.

taywan

iTrader: (53)

I'm curious to find out what the issue is. I have the same issue w a new built block.

I'm assuming you're going to pull the front cover to chk the chains, tensioners etc.

i8acobra

iTrader: (6)

When you pulled the plugs out, was there oil on the top half of any of them? When the spark plug tube seals (built in to the valve covers) go bad, oil leaks into the tubes and causes misfires.

zyou8er

iTrader: (1)

No oil, i even tried a different set :/

zyou8er

iTrader: (1)

Yeah, once i get a chance. Been working 12hr shifts six days a week. I'm really thinking that i skipped a tooth on the chain when i did the water pump. G-d willing next week i will get a chance to pull the covers off.

zyou8er

iTrader: (1)

FINALLYYYYY. I guess the chain skipped a tooth when i did the water pump.

qew

iTrader: (1)

Nice,so it was the chain when u did the pump.I just saw your post,i would have guessed the same if you said you did the water pump. I have a random misfire code due to bigger cams,researched and saw its quite common on many cars when going to a bigger cam.No actual misfire is felt just throws out the code.Anyhow thanks for the update.

zyou8er

iTrader: (1)

Yeah, it was off by one tooth. That explains why the driver side bank had 190psi, and pass side was 15psi lower.