1999 Maxima with rough idle

[jayhud007]

I have a rough idle on my 99 when my fan is also running. Before I go in and start tearing thigns apart, does anyone have an idea?

Also, I want to replace my current manual shifter. Any suggestions? I want to go to a short shifter.

Thanks.

[loystock]

We need further clarification about the rough idle. So does it mean that the engine idles normally if the fan is off?

[jayhud007]

when the car is idling with the fan running, there is a real rough idle that shakes or vibrates the vehicle.

when I turn off the fan, ac, furnace, the rough idle smooths out and no more shaking or vibrating.

its a 99 SE, with a 5-speed manual.

[loystock]

So the fan you are referring to is the AC blower motor and not the cooling fans (for radiator/condenser).

The problem may be a failing AC clutch or compressor. To verify, turn off the AC and blower (fan) and then start the car. Once the engine is running and idling smoothly, turn on the blower (fan). Idling should remain smooth. Turn ON the AC - if the idle becomes rough, the problem is with the clutch and/or compressor. The clutch assembly can be replaced w/o breaking the AC cooling lines. Replacing the AC compressor requires breaking the cooling line (freon may escape into ATM w/o proper equipment) and must be handled by certified AC shop.

[jayhud007]

Thanks for the info. I really appreciate the help. I'm going to take a look at it this week when I have a free night and see what's going on.

Any other suggestions out there?

[jayhud007]

one more item i forgot to mention earlier.

when the outside temperature is around 20 or lower, the rough idle does not happen.

[loystock]

The compressor operates above 35F (2C). So at ambient temp of 32F, the compressor will not engage and thus your idle is smooth. So it looks like the problem is with the AC compressor and/or clutch failure.

[NutriaforBreakfast]

Look in section for AC in the FSM and get your AC compressorreadings for the hi and low side

You can rent the manifold guages at Auto Zone and hook to the AC systemand check to see if your compressor is putting out.