Good Morning,
I have a 2001 Dodge Neon with 150,000 miles. For the past 8 months it vibrates when at idle ( traffic light, stop sign, etc)
No one seems to be able to find the problem. I have gone through 5 upper motor mounts, 2 lower motor mounts & 1 transmission mount in that time period. It does not hesitate, does not lack power and is otherwise a very good car. Does anyone have any ideas as to what could be causing this problem ? Thank you very much and have a good day
Jim...

 

Jim: welcome to the forums. Is the idle speed set correctly? Sometimes when the idle speed is too low, it will vibrate due to the small engine size. Conversely, on a larger engine, say a v-8, the balance is spread out over more cylinders, thus less vibration.

 

Good Morning Larry & Thank you,
I don't think the idle is adjustable. I have not seen any adjustment screws anywhere. I forgot to mention that when I put the car in neutral or P, the vibration is almost gone. Also, when I turn on either the ac, vent or rear defroster, it really vibrates. It's driving me crazy. Thank you again
Jim...

 

Aahh, information is sublime. Your computer is supposed to compensate for the activation of the a/c compressor, which is actually an added drag to the engine. Even in the defrost mode, the a/c compressor is activated to dry the air. I would opt to go to an Auto Zone or other parts dealer and have them run a diagnostic check. They usually charge a minimal amount for this, and they can interpret the problem. Of course it would be up to you to fix it, but at least you would know what was wrong. It may be something as simple as clearing the codes, which they can do also.

 

Hey Larry,
Already had the car scanned and it came up empty. No codes, no engine light on, no nothing. If the idle is adjustable, where would the adjustment screw be located ?
Thank s again,
Jim...

 

When was the last time your throttle body & especially your IAC motor & port was cleaned? Your IAC motor, located next to,or near your TP sensor (throttle position), is mounted usually with 2 torx screws, to the throttle body. The IAC motor (idle adjustment control) raises your idle speed when a load is present, such as a/c compressor, power steering pump load condition etc. Quite often you can remove it, and clean it, as well as the mating surface in your throttle body housing. If that doesn't cure it, you may be into a new IAC motor. ( http://www.autozone.com/az/cds/en_us...rInfoPages.htm ) See figures 10-13 at this link, it should be of assistance to you.

 

Hey Mike,
Funny you should mention the IAC & the throttle body
I cleaned them both about 3 months ago and it appeared to have 'calmed down' a little,(briefly for a day) but not completely. Perhaps it's time to replace the IAC ? Thanks for the autozone link.
Have a good evening
Jim...