I have a panel type K & N filter in my 89 GXE. The idle is generally okay (fairly smooth) but sometimes it drops off noticably then goes up higher than normal. Any suggestions?

 

My 1990 SE does that as well. It seems like the 3rd gen Max is especially sensitive to accesory drives changing the RPM, i.e. when you turn off the headlights, the rpm on my car goes up to approx 1400 before settling back down to 1000 or so. It's probably just the ecu seeing the rev's drop more than normal and trying to compensate by giving a slightly faster idle...

-V

 

The reason I was wondering if something is wrong with the MAF or other sensor (such as O2 sensor) is that it runs perfectly normal with the stock Nissan air filter.

 

Only things I can think of are:

1. The K&N might be over-oiled and the oil might be coating the hotwire sensor on the MAF causing erratic readings. When you change back, the MAF is able to burn off most of the contaminants and thereby get a good reading.

2. The air going through the K&N filter is turbulent and not as smooth as the air going through the factory filter. The erratic air movement could be causing problems with the air flow meter readings, which is why when people use the cone type filters, I normally recommend a velocity stack/air horn style adapter so that air is smoothed as it enters the MAF.

-V

 

The 3rd Gens (VG) don't like the panel filters. They lean themselves out at idle due to what vmok states in the second point. I would suggest changing to a CAI or similiar type.

Brent.

 

Pardon my ignorance but does the factory (K& N) "over-oil" their filters? If not, the cause of the erratic idle must be the turbulence you mentioned because I've never oiled it. I assume there is no velocity stack/air horn for the panel filter?