P0300
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From: Virginia
P0300
Been trying to diagnose this p0300 that won’t go away , the car drives fine , only has a slight misfire at idle . 2003 350z only modification on engine is an aftermarket air filter . The left muffler has a hole from the hanger breaking so there is a small but noticeable exhaust leak. I’ve replaced spark plugs with ngk , checked for bad coils , made sure 4&6 isn’t backwards , I’ve replaced all the intake gaskets , 150psi compression on all 6 cylinders, cleaned tb & relearned ,new valve covers , new pcv, new itachi ( oem ) (2) camshaft posisition sensors and the 1 crank sensor. Only codes I’ve ever seen/cleared is p0300 and p1516 . Maybe I’ll replace the fuel injectors , & fuel pumps next $$$$
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From: Carrollton, GA
I would test the injectors before replacing. Props for doing a proper amount of triage before asking on the forum though!
It looks like you had the upper plenum off, in order to do the valve cover install. Are you aware of the pattern for torquing down the bolts? That could be an issue. I would let the engine idle, and spray around the intake manifold (probably where lower and upper halves meet) with throttle body cleaner, and see if it affects the idle.
I've got a link to the Motordyne downloads here in case you don't have those. Good luck! https://motordyneengineering.com/manuals/
It looks like you had the upper plenum off, in order to do the valve cover install. Are you aware of the pattern for torquing down the bolts? That could be an issue. I would let the engine idle, and spray around the intake manifold (probably where lower and upper halves meet) with throttle body cleaner, and see if it affects the idle.
I've got a link to the Motordyne downloads here in case you don't have those. Good luck! https://motordyneengineering.com/manuals/
Last edited by jellofuel; Feb 25, 2018 at 09:18 AM. Reason: typo
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From: Virginia
I would test the injectors before replacing. Props for doing a proper amount of triage before asking on the forum though!
It looks like you had the upper plenum off, in order to do the valve cover install. Are you aware of the pattern for torquing down the bolts? That could be an issue. I would let the engine idle, and spray around the intake manifold (probably where lower and upper halves meet) with throttle body cleaner, and see if it affects the idle.
I've got a link to the Motordyne downloads here in case you don't have those. Good luck! https://motordyneengineering.com/manuals/
It looks like you had the upper plenum off, in order to do the valve cover install. Are you aware of the pattern for torquing down the bolts? That could be an issue. I would let the engine idle, and spray around the intake manifold (probably where lower and upper halves meet) with throttle body cleaner, and see if it affects the idle.
I've got a link to the Motordyne downloads here in case you don't have those. Good luck! https://motordyneengineering.com/manuals/
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Joined: Jul 2017
Posts: 159
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From: Carrollton, GA
If that doesn't apply, I see you cleaned the throttle body - maybe try the ECU relearn to resolve any potential issues with the TB.
If those don't apply, you can test the injectors. Or if you think an injector might be clogged, I recommend Redline SL1 or Gumout Regane (with PEA's on the label) to clean them out.
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From: Virginia
Ok, I would eliminate the free things to check before buying new injectors. If the issue started occurring after you swapped in the high-flow filter, I'd swap a paper one back in, and do ECU relearn.
If that doesn't apply, I see you cleaned the throttle body - maybe try the ECU relearn to resolve any potential issues with the TB.
If those don't apply, you can test the injectors. Or if you think an injector might be clogged, I recommend Redline SL1 or Gumout Regane (with PEA's on the label) to clean them out.
If that doesn't apply, I see you cleaned the throttle body - maybe try the ECU relearn to resolve any potential issues with the TB.
If those don't apply, you can test the injectors. Or if you think an injector might be clogged, I recommend Redline SL1 or Gumout Regane (with PEA's on the label) to clean them out.
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From: Virginia
sorry I forgot to mention that I acquired the vehicle with the p0300 code and rough idle . I figured it’d be an easy fix LOL ya right. I also used wynns fuel 2 part injector service inside the gas tank and inside the intake. That didn’t make any difference. One thing I noticed is SOMETIMES on cold starts there is white smoke and smells like strong gas smell.
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From: Carrollton, GA
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From: Virginia
Misfire is finally fixed after replacing all 6 fuel injectors , I have not checked resistance on the old ones or inspected the o-rings. Been driving the car to work past couple days and no codes coming back, smooth idle and very happy owner
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