Engine Noise @ Idle + In Gear

My '97 SL2 makes a vibration noise at idle plus
when in gear. Can hear it when waiting at traffic
light. (Comes from left side where belts, pulleys, etc are located.) I can
take it out of gear & it goes away. Any troubleshooting help would be
great.

 

Automatic or manual transmission?

The upper motor mount wears out every few years, and there is a lower
one too (which doesn't wear out nearly so fast.). The lower one can be
clearly seen if you take off the wheel and pop-off cover. If you've
got a valve cover oil leak, the oil all ends up on the lower motor
mount which causes the rubber to swell and the mount becomes
ineffective.

There's a similar mount on the transmission. Maybe this should be
suspect as it only does it in gear.

If the noise were squealing instead of vibrating, I'd suggest the belt
idler and tensioner.

Tim.

 

You need to be more clear on the sound. Does it change sound with engine
idle speed? If you take it out of gear and put in neutral does it go away?
Is the idle extremely rough? Any other drivability symptoms?

Without more info, I would start with a complete tune up and a very thorough
throttle body cleaning. I would also replace the ignition wires if they
have not been changed within the last 3-4 years. I would also make sure the
air filter is clean/fairly new and throw some good fuel injector cleaner (I
like Techron) into the gas tank too. This should smooth out any rough
idling and improve fuel mileage too.

If the "vibration noise" is due to a worn bearing, then you need to
determine what is causing the noise. It could be water pump, alternator,
air conditioner compressor, power steering, or even the tensioner or pulley.

If it something more mechanical that is banging, then check to make sure it
is not the exhaust pipe rattling against the body or a support.

As a last thought it might be a worn out Torque Axis (top of engine) motor
mount, but these usually give other symptoms, like a clunking when shifting
between gears.

Bob

 

As a last thought it might be a worn out Torque

In my personal experience, the top motor mount being worn gives
vibration in idle. It's felt through the steering wheel in particular
for me, although I'm sure others can cite their different symptoms.

The lower motor mount being worn out leads to clunking when shifting or
accelerating.

Usually the onset of these symptoms is gradual so that you get used to
it and don't notice it until you look for it. In my case, I changed
both motor mounts last spring and I was amazed at the difference it
made. I had actually grown used to the vibration at idle and clunking
when accelerating/shifting to the point that without their cues, I
wasn't sure that I was even moving!

There are also mounts on the transmission side. And there's this funny
stiffener between the engine and transmission, too. But I haven't
messed with those.

Tim.

 

Bob Shuman:
It does not change with idle speed. No extreme high idle sounds. I gave
it a tuneup w/ wires & plugs. Air filter fairly new. Tried injector
cleaner, it gave better mileage. It is more of a vibration noise, coming
from engine area. Will look at worn bearing ideas. However, have not had a
throttle body cleaning, but when I do give it some throttle, it seems to go
away. Will look at this too. Thanks.

 

The throttle body cleaning is just regular preventive maintenance so should
be done every 12-18 months or so depending on miles you drive annually. I
was thinking it may be causing a rough idle, but it does not sound like you
are describing that, so I'd look at the rotating wear items that I mentioned
previously. Start with the Air conditioner since it will sound different
when the clutch is engaged or not. You can sometimes spray each of the
bearings one by one with some silicone lube and they may quiet down for a
few minutes helping you to identify the source. This is only a temporary
fix and will not solve your noise problem. You can also use a stethoscope
or make something up to accomplish the same by holding a solid item to each
of the accessories and seeing if you can locate the source.

Good luck and do post what you find for the benefit of others.

Bob