Nismo3366 posted on another thread about a page that talked about only using nissanmatic C tranny fluid to prevent slow shifts when it's cold. On the same page, I read this:

Rough idle: Idle fluctuation may result from the use of the wrong air filter, or if the original air-filter housing was not replaced with a revised unit for a funnel-shaped filter. (1990)

Anybody ever hear anything about this? The "funnel shaped" filter reference is especially interesting.... almost like they are saying that the dealer/manufacturer is recommending a cone filter?

 

Yup. My bro had put a JWT cone on his vg 5-sp and it didn't like it. So he put his oem filter back on. If you think the idle is bad, try a cheap paper unit in the stock airbox

 

i never heard of the stock airbox being replaced with a funnel shaped filter...but i read about the tsb at school while i was trying to fix the rough idle on my maxima...i had a k&n filter in my stock airbox...so i read that and replaced it with a fram paper filter...i did nothing...i still have a rough idle

the reason why nissan said that the wrong air filter will cause rough idle is becuase it could cause turbulent airflow which would cause the maf not to pick up all of the air flowing through it

 

i put my stock air box back on recently.. and i've noticed the idle was rough. before when i had the cone filter in place it was fine.

 

I guess I was reading it the other way around, where it was saying that you would get BETTER idle by changing to a cone filter. I see some people are saying yes, some no. Anyways, I usually run a STP or FRAM filter in the stock airbox- does that qualify as a cheap paper one?

Also, my next/first mod is probably going to be the intake piping with a cone filter, so that's why I thought that statement was interesting.