P0300 multiple cylinder misfire

Tiny
JASON COX
  • MEMBER
  • 1997 INFINITI QX60 HYBRID
  • 3.3L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 240,000 MILES
Ran OBDII scan tool and got codes P0325 and P0300. Car runs great after sitting over night or for a few hours. Once warm it starts missing. Installed new distributor. Trying to set the timing but I have turned the distributor as far as it will go, but the distributor hold down bolt will not let me turn it anymore to get in time. Is my distributor installed wrong? It is an aftermarket distributor and not a authentic Nissan part I installed. I set the engine on TDC compression stroke put my rotor facing spark plug number 1 but can't turn the distributor any further due to the hold down bolt. It starts up every time but misses like crazy. If I accelerate the miss goes away but comes back when stopped. In Drive and Reverse it misses real bad. Please help. P0300 code will not go away.
Monday, March 20th, 2017 AT 4:13 PM

7 Replies

Tiny
STEVE W.
  • MECHANIC
  • 15,233 POSTS
P0325 = Knock Sensor Circuit Malfunction Check the wiring to the sensor, it may be unplugged or have a bad connection. If you have a scan tool that can watch live data you can sometimes watch the knock sensor signal and tap on the block next to the sensor to see if it reacts. If the engine senses a constant knock it will retard the timing.

Check the distributor, With it installed bring #1 up to TDC. Now rotate it so the timing pointer is around 15 degrees. Does the rotor point at # one post? If no will it rotate so it does? If not you need to re-install the distributor. If it does line up, you have a different issue.

Check for a vacuum leak as the issue of missing at idle that goes away when you rev up is a classic symptom of a leak.
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Monday, March 20th, 2017 AT 5:11 PM
Tiny
JASON COX
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  • 5 POSTS
I will check and get back to you. Another question. So will a vacuum leak cause a P0300 multiple miss fire code?
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Monday, March 20th, 2017 AT 6:21 PM
Tiny
JASON COX
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  • 5 POSTS
Also when sitting at idle and in Park if I stomp on the gas quickly to rev it up it dies
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Monday, March 20th, 2017 AT 6:38 PM
Tiny
STEVE W.
  • MECHANIC
  • 15,233 POSTS
Vacuum leak can cause random misfires because it leans out the mixture. So one cylinder may get a good mix but the next gets a lean mix. As the engine speeds up it generates less vacuum and the leak doesn't matter as much. Lean mix can cause it to die as it doesn't get enough fuel to keep running.

I would also do a back pressure test on the exhaust. A plugged or failing system can mimic a vacuum leak because the exhaust cannot get out which chokes the engine.
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Monday, March 20th, 2017 AT 9:48 PM
Tiny
JASON COX
  • MEMBER
  • 5 POSTS
How do I do a back pressure test?
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Wednesday, March 22nd, 2017 AT 10:17 AM
Tiny
STEVE W.
  • MECHANIC
  • 15,233 POSTS
Remove the first O2 sensor before the convertor, then you need an adapter and a simple pressure gauge something that reads from 0 to about 30 PSI is great. Screw the adapter into the hole and attach the gauge. Start the engine and read the gauge at 1000 and 1500 rpm. 0-no more than 2 psi is good. 2 psi and up is not good. Especially if it keeps rising. Now check the other bank the same way. If you see a high reading, test in the port after the convertor. If that tests high as well, it's probably the muffler, If the after cat test is lower then it's a plugged cat.
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Wednesday, March 22nd, 2017 AT 4:29 PM
Tiny
JASON COX
  • MEMBER
  • 5 POSTS
Thank you so much. I will get back to you and let you know the outcome
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Friday, March 24th, 2017 AT 7:23 PM

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