Engine Idle Noise (1 Viewer)

[ghong14]

Hi everyone,

I noticed a low humming noise in 98LX470 during idle. It seems to be present with both the air condition on and off. The RPM with and without air condition “on” when car is in park seems normal. No noise when car is put in drive.

Would appreciate any expertise.



RPM with air condition

RPM without air condition

 

[spmarfatia]

power steering pump?

check PS fluid level?

 

[ghong14]

power steering pump?

check PS fluid level?

Power steering checks out. Fluid level normal.

 

[nissanh]

Remove the drive belt and check.

You'll also need an OEM battery positive post. The battery post you have installed are well known to cause voltage drop as much as 0.5 V.

 

[ghong14]

Remove the drive belt and check.

You'll also need an OEM battery positive post. The battery post you have installed are well known to cause voltage drop as much as 0.5 V.

I believe the battery positive post is OEM. The yellow cable is connected to the front fog lights.

What can happen when the voltage drops?

 

[nissanh]

Both the positive and negative terminals are aftermarket. The OEM part number for positive is 90982-06022. I would attach the yellow wire to nut on the terminal and not on to the main 12 mm bolt. Also get an Auto fuse holder and replace the fuse holder I see you have on the yellow wire (it is used for audio install). The negative terminal has been broken, so you have to use a good aftermarket terminal (not what you have).

A voltage drop can cause many things. Most electronics are run on mV signals. A drop in voltage can cause some mV drop and inform the ECU to act incorrectly.

You can check a voltage drop by using a simple volt meter. Set the unit to measure 20V DC. Place the negative terminal in the multi-meter on the butterfly nut, and positive wire on the multi-meter on the battery post (not the terminal, just right on the post). the reading should be 0.00 V.

 

[ghong14]

Both the positive and negative terminals are aftermarket. The OEM part number for positive is 90982-06022. I would attach the yellow wire to nut on the terminal and not on to the main 12 mm bolt. Also get an Auto fuse holder and replace the fuse holder I see you have on the yellow wire (it is used for audio install). The negative terminal has been broken, so you have to use a good aftermarket terminal (not what you have).

A voltage drop can cause many things. Most electronics are run on mV signals. A drop in voltage can cause some mV drop and inform the ECU to act incorrectly.

You can check a voltage drop by using a simple volt meter. Set the unit to measure 20V DC. Place the negative terminal in the multi-meter on the butterfly nut, and positive wire on the multi-meter on the battery post (not the terminal, just right on the post). the reading should be 0.00 V.

Good news I did the test on both the positive and negative side of the terminal and the readings are both zero. However, I did notice that the veichle's battery is at 12.3V. This is a brand new battery so something is causing the battery to drain when car parked and not used. Will definitely get new terminals for the veichle and probably do a swap of the battery at Costco.

 

[nissanh]

Good news I did the test on both the positive and negative side of the terminal and the readings are both zero. However, I did notice that the veichle's battery is at 12.3V. This is a brand new battery so something is causing the battery to drain when car parked and not used. Will definitely get new terminals for the veichle and probably do a swap of the batt

That's good.
12.3 V is not bad. Perhaps the meter you used to measure the voltage is not calibrated. Try a a new 1.5 volt battery and see what it shows.

 

[100d ua]

It's definitely a pulley. I'll never forget that sound.

Watch the first 2 minutes of this video:

 

[ghong14]

It's definitely a pulley. I'll never forget that sound.

Watch the first 2 minutes of this video:

Thanks! This is super helpful! Which pulley did your car end up giving the problem?

 

[ghong14]

That's good.
12.3 V is not bad. Perhaps the meter you used to measure the voltage is not calibrated. Try a a new 1.5 volt battery and see what it shows.

Although I noticed that my alternator charge did not do so well.

Unloaded 12.78
Loaded 12.47

May be the alternator pulley that is causing the noise too.

 

[100d ua]

Thanks! This is super helpful! Which pulley did your car end up giving the problem?

For me it was the alternator and then shortly after the power steering pump.

 

[ghong14]

For me it was the alternator and then shortly after the power steering pump.

Were the noises similar. Any chance you can discern which mine reminds you of?

Regarding the alternator, you have any indicator lights that popped up?

 

[sockeyesalmon]

upper radiator hose is installed backwards

 

[100d ua]

Were the noises similar. Any chance you can discern which mine reminds you of?

Regarding the alternator, you have any indicator lights that popped up?

Nope.

 

[ghong14]

Nope.

Looks like a nice 12 inch screwdriver?

 

[100d ua]

Looks like a nice 12 inch screwdriver?

That’s what she said.


… yeah it’s 12”…

 

[ghong14]

I think the culprit is the alternator. I also noticed today that when the switch headlight from the off to on position the voltmeter jumps quite a bit. Is this normal?

 

[ghong14]

That’s what she said.


… yeah it’s 12”…

I ordered a 16 inch screw driver. Will do the test your suggested.

 

[100d ua]

I ordered a 16 inch screw driver. Will do the test your suggested.

Just be very careful poking the screw driver around so it doesn't get sucked into the belt and check all the pulleys. Some of them can sound "rough" but not necessarily be the culprit.