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Discussion Starter #1
I have replaced spark plugs, wires, distributor cap, fuel filter, fuel injectors. Injector wire harness read 12.26vdc to ground. Removed spark plug #2 and wire, clean. The truck has 210k miles on it. Anything I'm missing? Any suggestion?
 

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Replace #2 plug if you haven't already. Can you temporarily swap on a different spark plug wire for #2, or simply temporarily swap #2 wire with #3 at both distributor and at the spark plug to see if the issue migrates?
 

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Discussion Starter #3
I have spark on #2 spark plug, using tester light. I also use probe test on Harness #2, it flashes with engine running. I also read 13.5 volt dc with my meter. Compression test on all 4 cylinder, 120-140 psi.
 

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Could be a leaking intake gasket. It's not unheard of on either the NAP-Z and KA24E engines. Head gasket is another possibility as is a valve issue, but failed intake gaskets are far more common. Let the engine idle and spray some carb cleaner around the area where the intake mates to the cylinder head and pay attention to any RPM flare ups while spraying.
 
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Discussion Starter #5
The P0302 went away but the check engine came up with 2 new code. P0300 and P0505. Just puzzle me, tested all plugs and they flashes with my tester also the injector tested with engine running, the harness had been tested with light and all flashes, read 13vdc with my volt meter. So now I have random misfire and P0505.
 

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Discussion Starter #6
I sprayed throttle/carburetor body cleaner inside and into the hole to AIC, I unplugged the harness to AIC and plugged back in and there was changed in air suction. The P0505 and P0300 went away but the P0302 came back. I followed your suggestion, sprayed lubricant around the base of the throttle especially the big L shape vacuum fitting going to the brake booster, the rpm changed or got quite.
 

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Sounds like you found your vacuum leak!
 

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Discussion Starter #8
One issue corrected. The pesky P0302 code will not go away. I almost replaced everything on this truck except the TPS ( rpm changed when I moved it left or right), the IAC or AIC (rpm changed when I unplugged or plugged it in). also noticed that the rpm when I pit it on drive, deep almost 250 lower but not dying. Any suggestion?
 

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Did you replace the throttle body gasket?
 

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Discussion Starter #10
No. I did not. The leak is coming from the L-shape pipe threaded vacuum fitting. I just put a sealant around the thread. I sprayed throttle body cleaner around with engine running, rpm did not change.
 

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The pesky P0302 code will not go away... Any suggestion?
Move the #2 plug to another cylinder. If the code follows the plug to another cylinder, the plug is bad.
Plugs can crack internally if over-torqued, or if dropped in transit before you even bought it. Plugs can operate differently under pressure vs a bench test.
 

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Discussion Starter #13
I already switch fuel injector from #2 to #1 and also spark plug #2 to #1 separately, still getting P0302.
 

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Your crank position sensor generates the signal for a misfire code and controls timing. They are about $20 (at RockAuto or AdvanceAutoParts) to replace, but be sure there is no oil contamination inside the wiring connection of the old part. This may also explain your unstable idle speed when shifting.
 

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Compression-good, spark plug and injector swap-no change and I'm assuming you confirmed spark exists at both plugs? If so, I would suspect a bad intake gasket.
 

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Discussion Starter #17
After replacing maf, tps and iac solenoid valve, and turning those adjustment screws, the truck idle rough and dies on cold start. Someone suggested that since I've replaced so many, try replacing the egr valve and egr valve solenoid. The truck idle is steady now but high on cold start, I should have left those adjustment Philip screws alone. These screws are between the throttle body and firewall. I think the first one on left is for the FIC, the middle one pointing to the side, not sure (maybe for rpm), the third one closest to the wall pointing up, not sure ( maybe adjust the roller cam). Any idea what are those Philip screws? 02 Nissan Frontier 2.4L A/T.
 

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Pictures would be helpful. You should be able to find those adjustments and how to adjust them in the "EC" section of the factory service manual for your truck. You can access that at Nico Club's site:

 

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Yes they are.
 
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