# Engine Misfiring....Need Help With Diagnosis



## SE-R420 (Jun 22, 2002)

A few weeks back i got an engine misfire code on cylinder #4. I found out that something had gotten into the cylinder and after removing the object, thank god there was no damage to the engine. I had to replace the spark plug in cyl #4 as whatever got into the cylinder crushed the tip of the plug. So I ended up buying 4 new spark plugs just to start fresh (I used NGK Iridium Plugs which are great). I also noticed a small leak in the exhaust header gasket by cylinder #4 (ironically). Soooo, I changed the gasket and now thats fine. I also had a compression check done to make sure im running the proper compression in every cylinder and the results were that every cylinders compression was equally normal. So now the engine is running better, BUTTTT I still notice random misfires, but the engine isnt shooting any codes. Its a lot more noticable when running low rpms and when im using the auxilliery systems (a/c, defroster, ect). I'm almost sure that its only misfiring one cylinder at a time, due to the time in between misfires (I can feel jerk a bit). So now Im dumbfounded, and dont know what it could be. The spark is good, the compression is good, and there appear to be no more exhaust leaks. I also took off the CAI filter and cleaned it and checked for any holes where things can get in and there are no holes and its now perfectly clean. The only other thing I'm thinking is possibly the A/F mixture could be off, but I really dont think so.

Any opinions? I'm really getting frustrated and hate having my car running like this.

Thank you in advance guys,

Michael


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## metro273 (Sep 16, 2005)

Ignition coils come to mind for some reason! Nissan has a history of crappy coils...


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## SE-R420 (Jun 22, 2002)

Where exactly are they located and what am I looking for?

Thanks


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## saint0421 (Sep 24, 2006)

SE-R420 said:


> A few weeks back i got an engine misfire code on cylinder #4. *I found out that something had gotten into the cylinder* and after removing the object, thank god there was no damage to the engine. I had to replace the spark plug in cyl #4 as whatever got into the cylinder crushed the tip of the plug. So I ended up buying 4 new spark plugs just to start fresh (I used NGK Iridium Plugs which are great). I also noticed a small leak in the exhaust header gasket by cylinder #4 (ironically). Soooo, I changed the gasket and now thats fine. I also had a compression check done to make sure im running the proper compression in every cylinder and the results were that every cylinders compression was equally normal. So now the engine is running better, BUTTTT I still notice random misfires, but the engine isnt shooting any codes. Its a lot more noticable when running low rpms and when im using the auxilliery systems (a/c, defroster, ect). I'm almost sure that its only misfiring one cylinder at a time, due to the time in between misfires (I can feel jerk a bit). So now Im dumbfounded, and dont know what it could be. The spark is good, the compression is good, and there appear to be no more exhaust leaks. I also took off the CAI filter and cleaned it and checked for any holes where things can get in and there are no holes and its now perfectly clean. The only other thing I'm thinking is possibly the A/F mixture could be off, but I really dont think so.
> 
> Any opinions? I'm really getting frustrated and hate having my car running like this.
> 
> ...



From ur screen name it's safe to assume that u have a SE-R/ or Spec V. Have you loctited your butterfly screws? Do you atleast have a header?

QR25DE Precat and Butterfly Screw FAQ - MSV


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## saint0421 (Sep 24, 2006)

SE-R420 said:


> Where exactly are they located and what am I looking for?
> 
> Thanks


He's referring to the coilpacks that you removed to access your spark plugs.


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## SE-R420 (Jun 22, 2002)

Yes, I have a 2003 Spec-V, and yes I have a header. Hotshot makes it. I also have a cold air intake, greddy exhaust, relocated knock sensor, stiff motor mounts, jwt clutch and flywheel, twm short shifter, balance shaft removal kit, and hondata intake manifold gasket. Just to give a breakdown of my setup. 

I have not checked the butterfly screws on the intake manifold.

I also have not checked the coil packed specifically but I briefly looked at everything when the plugs were being changed and saw no wear on anything there, and my mechanics diidnt bring it up either.

So im guessing the next step is to check the butterfly screws....

What if thats not the problem??

thx


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## metro273 (Sep 16, 2005)

^^^Headgasket!


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## SE-R420 (Jun 22, 2002)

what about the gasket? check for leaks? ive never heard of spec-v's having head gasket leak issues. I also only have 55k miles on the car.


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## saint0421 (Sep 24, 2006)

SE-R420 said:


> what about the gasket? check for leaks? ive never heard of spec-v's having head gasket leak issues. I also only have 55k miles on the car.


Some Spec-Vs have headgasket issues. 

Some symptoms range from slight to very noticable coolant loss. A small leak into cylinder can cause misfire. Constantly fouled plugs or wet when pulled. You can accurately determine the overall health of your engine with an oil analysis from blackstone labs. They have all pertinant info on their site.

Blackstone Laboratories

Still check your screws. While you're in there I would loctite them as well. 

My SpecV - Your Ultimate Nissan SE-R Spec V Resource / Info


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## metro273 (Sep 16, 2005)

^^^Thanks for explaining the headgasket issue with these 2.5s!


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