[MEvinson]

Hi Everyone,

I have a 2004 Nissan Sentra Se-R SpecV. I am new to these types of performance cars. I am use to old muscle cars. I am having an issue with my Se-R it is registering SES code P0300 (Random multiple misfire). I had two coil packs going out on it so I replaced all four coil packs with Denso coil packs and all four spark plugs with what was recommended form Nissan. But I am still getting the P0300 code. The misfire is not noticeable while driving. It is only noticeable when idling. The car will be idling around 900 rpm and then drop and act like it wants to die. I have also noticed a rattle sound coming from the exhaust when I'm shifting and rpms drop. This also happens when I rev the engine in neutral and it rattles in the exhaust when rpms are dropping. So a little more about the car. It has an after market exhaust with the pre-cat gone.

Thank you for your help.

 

[i68k]

if you have a specv, sometimes what is recommended is actually a downgrade. the specv comes with iridiums from factory, but the fsm recommends platinum for all older qr25. however, you still shouldnt have misfires.

as for your exhaust, you should still have the secondary cat, unless you deleted that one as well, so it couldve blocked up and dislodged on you, or if you have a good leak, you will notice in your idle. if its just a heatshield making the noise, you shouldnt see any change in idle. only when exhaust flow is being obstructed, or large leak, it will affect idle.

otherwise, having a 900 idle is very high, meaning something else is probably causing the ecu to adjust trim or idle, unless of course youve set it to 900 for some other motor modifications. if its the case that it was set high, and the normal relearn procedures may reset it to a lower idle, between ~650 ~750ish is normal idle. so if you dont have say an upgraded 04-06 maf, vq35 throttle body, cams or other internals, etc, there is no reason to have a high idle. if everything is in stock trim, you can try doing all 3 relearns to reset your pedal, throttle plate, and idle air readings using the procedures in the fsm.

things that could be affecting your idle are numerous, but starting at the top, make sure youve checked your vin for recalls, as there are crank position sensor and ecu reprogram recalls, which is possibly affecting your idle and causing misfires. if you do replace the crank sensor, replace the cam sensor as well, it has the same symptoms, and is the same part. since youve deleted the precat, hopefully you didnt suffer from the effects of having one, so a simple compression test, followed by a leakdown if necessary should give you actual results of headgasket failure.

the coilpacks are rebuildable, as long as the ignitor works, you can change the springs and capacitors with a rebuilt kit from nissan. so dont be afraid to search or ask for questions, for an example: maybe your front caliper seized and you wouldnt mind a bolt-on 2 piston caliper upgrade for a similar price

EDIT: always make sure your battery terminals are tight, and it has good ground contact, be sure to check your voltage motor on & off to observe the charging system. just to be sure you dont have a bad ground, as a result a bad battery ground can ruin the charging system or cause the grounding point to be your coilpacks, or even your ecu causing ecu failure. there are many voltage specific sensors, unlike those solid older muscle cars

 

[yogi b]

crank or cam sensor
imo