Please help: G35 p0300 problem
#47
05-26-2012 | 04:41 PM
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A lot of work wiyh no results that sucks! sounds like you have low vacuum from what you say which means back to the engine not running right, Did you look at the pics of coil grounds at front of engine? Not a big deal to clean these 2 bolts try that, the injector grounds are behind the glove box, sorry no pics for this. If you can describe what the code means, that might help. I'd go with the coil ground first take 10 min. 
#48
08-02-2012 | 05:13 PM
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From: o-town & west palm beach FL
I'm wondering If I have a bad or stuck injector. I just did 101 miles in one tank! And ive been having hard starts the past few days. The only code I have is p0300. I'm going to try to clean the fuel level in the tank and try to read the injectors if I can find an injector probe. The injectors have only been on for about 3k miles. Sometimes the code does clear itself
#51
06-22-2017 | 11:43 PM
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P0300
I currently have a infinity g35 and it has the code p0300 when I start the car it runs fine after I drove for 13 min. And come to a stop I have to fight it to stay alive then this code pops up and the check engine light starts flashing when it gets to die there is an engine knock but after I rev it the knock stops and it runs fine it was in a flood and I tried to check for a misfire the spark plugs seemed alright no water in the oil and the water didn't get up to the MAS I'm at a loss any help would be great
#53
06-23-2017 | 03:18 PM
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I tried to do a misfire counter but snap on doesn't have one the code is multiple misfire detected
#54
12-04-2017 | 12:39 PM
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Misfiring, engine light, air sensor, idle running rough
Okay guys I have a vq35hr the car was having the same issues everyone here seems to be complaining about as well as the noise in the exhaust which did make me think it might be a clogged catalytic converter I've heard that causes the car to run like s*** somewhere on here I read that if you clean the intake sensor that it would probably stop the misfiring and the ink and acting up so I figure I'd start with that I took the intake apart and what I noticed was the air filter was blocking the air intake sensor after noticing this I replace both air filters and the car runs perfect now
#55
10-08-2018 | 03:12 AM
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2004 G35 MT started misfiring about a month ago, engine would shutter then go back to normal. A couple of weeks ago while idling the engine it went into misfire mode and the Service Engine Soon light turned on. Engine code was P0300. Replaced coils and spark plugs. After replacement engine continued to misfire. Took a break and the following morning rechecked all the coil connectors. Cylinder 4 and 6 was NOT seated all the way in. The probably was due to the new coil connector not fitting exactly. Things to note, replace coils and spark plugs one at at time as I've seen some posts where coil connectors to cylinders 4 and 6 were crossed. Also mark your old spark plugs and coils with the cylinder number for reference. For example if you noticed one of your spark plugs was extra dirty that may lead to a possible defect with that cylinder fuel injector...etc..
#56
04-13-2019 | 12:38 AM
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2004 g35 2wd
This was my fix... After the po300.
Did you check the gap on your spark plug? What spark plugs did you get - models would be helpful. If they're the platinum plugs like recommended in the manual (PLFR4A-11, PLFR5A-11, or PLFR6A-11) you should be gapping them to 0.044". They are supposed to come pre-gapped (to 11mm or 0.433 inches, as is shown by the model number) but sometimes when they're being moved the gap gets adjusted.
That would be the first thing I'd check. Secondly, remove your engine cover and intake and check to make sure you have the cylinders corrected in the right firing order! You may not think you could actually mess this up but when I changed my spark plugs I did switch 4 and 6 on accident as I was talking to a friend of mine. Started it up and it immediately felt rough and went ahead to switch them.
If you look at the harnesses going to the ignition coils, there will be two wires with the same color and the wire that is on top (when the harness is connected to the coil) should be different on each one. This is the ignition signal wire going to your ECU. If everything is wired up correctly, cylinders 4 and 6 should have the same color wire, but 6 should have a red tracer and 4 should not. If you see a tracer on the harness connected to 4, switch them. Because of the way the connections come off of the main harness, it can be easy to switch the two if you're not paying much attention.
Lastly - try not to drive your car much in this condition. Misfires and can be detrimental to the life of your engine. Try to diagnose it before you continue driving.
That would be the first thing I'd check. Secondly, remove your engine cover and intake and check to make sure you have the cylinders corrected in the right firing order! You may not think you could actually mess this up but when I changed my spark plugs I did switch 4 and 6 on accident as I was talking to a friend of mine. Started it up and it immediately felt rough and went ahead to switch them.
If you look at the harnesses going to the ignition coils, there will be two wires with the same color and the wire that is on top (when the harness is connected to the coil) should be different on each one. This is the ignition signal wire going to your ECU. If everything is wired up correctly, cylinders 4 and 6 should have the same color wire, but 6 should have a red tracer and 4 should not. If you see a tracer on the harness connected to 4, switch them. Because of the way the connections come off of the main harness, it can be easy to switch the two if you're not paying much attention.
Lastly - try not to drive your car much in this condition. Misfires and can be detrimental to the life of your engine. Try to diagnose it before you continue driving.
#57
05-12-2020 | 12:46 PM
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G35 Coupe Manual 180k
Problem solved?
I'm currently haveing issues with my 2004 G35 sedan 6mt rwd. It is currently throwing a P0300 fault code for multiple/random cylinder misfire, around 3000 rpm the ses light will begin to flash. Symptoms other than the misfire are high idle black smoke from unburnt fuel, and lastly if i am driving say around 2000 rpm and push the clutch in the idle will drop to 1000 rpm bounce back up to 1500 rpm and the settle back at 1000 which is high(car used to idle around 700rpw). I have recently changed driverside valve cover (leaking tube gaskets) intake gasket and center plenum gasket and all 6 spark plugs (used NGK). Had the car diagnosed and is saying that the misfire is coming from the number 6 cylinder so that coil has been replaced and still no difference in how the car runs. I am new to the nissan/infiniti world and have no ideas of where to look next any ideas would help. Thanks, Sam
did you ever get this problem solved and what did you have done? I’m looking at possibly buying an 04 and it’s throwing the same code, wondering if it’d be worth it
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Patrice Magnan (09-11-2020)
#58
05-12-2020 | 01:37 PM
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The wire harness on the G and Z are poorly assembled which over time results in friction between the wires. My mechanic had to strip down the entire wire harness and inspect for and shorts. Next the ECU was the culprit resulting in a replacement ECU being installed.
#59
05-30-2020 | 07:36 PM
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