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P302 Cylinder 2 Misfire - Injector or Vacuum leak?

Old 03-01-2019, 12:39 PM
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Waffeey
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Default P302 Cylinder 2 Misfire - Injector or Vacuum leak?

Hi all! Just picked up a Silver 2003 Nissan 350z Touring 6spd Coupe two weeks ago and after falling in love with the car it a CEL has appeared! I have put around 400 miles on the car already and it was flawless up until now. It's a p302 cylinder 2 misfire code plus an occasional pop audible from the exhaust at idle, i have to get out of the car to hear it. The car still runs fine and has power, no flashing CEL to indicate a dead misfire. I have swapped the coil pack and spark plug between cylinders 2 and 4 and after clearing the CEL it had developed a pending code on cylinder 2 once again. Both plugs looked normal. Is this more likely to be the intake plenum gasket or injector? I have put around 400 miles on the car already and it was flawless up until now.
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Old 03-01-2019, 12:41 PM
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Sorry if this is not posted in the right place also, I'm new here! Any feedback would be greatly appreciated.
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Old 03-01-2019, 03:46 PM
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Spike100
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You have done a good job eliminating the usual suspects (i.e., ignition packs and spark plugs).

The next most likely cause for your misfiring problem is fuel delivery: Either not enough fuel or inadequate pressure. The pressure inadequacy might be a problem with the fuel injector (and that might be a vacuum problem or a mechanical issue with the injector).

There is a test sequence for this. Google a description and you will see many solution descriptions.
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Old 03-02-2019, 12:46 AM
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Originally Posted by Spike100 View Post
You have done a good job eliminating the usual suspects (i.e., ignition packs and spark plugs).

The next most likely cause for your misfiring problem is fuel delivery: Either not enough fuel or inadequate pressure. The pressure inadequacy might be a problem with the fuel injector (and that might be a vacuum problem or a mechanical issue with the injector).

There is a test sequence for this. Google a description and you will see many solution descriptions.
Thank you for the responce! A bad injector was what I was thinking it was going to be as well so I swapped cylinders 2 and 4 injectors to confirm the misfire follows and replace the plenum gasket set as well while I was at it. Once i was done I did the ECU reset and throttle relearn procedures since I cleaned it all and BOOM! Purring like a kitten and no more CEL!! Must of had a very slight vacuum leak causing cylinder 2 specifically to pull in too much air and lean misfire. Absolutely love working on these cars. So happy to have a healthy VQ again!
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