what kind of a question it that ? What has the A.C. to do with anything ? Maybe your brake rotors are warped ? How
long is a piece of string ? Your going to have to supply
a lot more info than that.

Okay, let me try again. Someone has helped me with my air conditioner problem earlier today. I also have another problem and it has nothing to do with the air conditioner.
I want to know if anyone can tell why do my car vibrates a little when I come to a stop at a traffic light. What causes it to vibrate alittle. Do I need a tune up?

I believe that what you are saying is that the car vibrates noticeably at idle when you are stopped and sitting at a red light with the car in gear. Also I think you're saying that this is new and your car didn't do this before.

Your correlation with the A/C might be valid. The A/C compressor adds a fair amount of load to an engine when it is engaged. With your car at idle and the additional load added with the A/C on and the compressor clutch engaged, the idle engine speed may dip which causes a resonance that results in a noticeable vibration. Without the extra load from the A/C compressor the engine can idle more easily and the RPMs go up enough to get out of the frequency that causes the "vibration" at idle. Smaller cars with smaller motors are more likely fell the lug of the A/C.

If your car runs well otherwise, I'd say your probably OK. A tune-up wouldn't hurt it, but it may not help either.

good luck

If the back tyres are unevenly worn, it will cause the steering wheel to shake as you come to a stop.

RE: Vibration
Posted by: kalining (My Page) on Thu, Jul 14, 05 at 18:29

what kind of a question it that ? What has the A.C. to do with anything ? Maybe your brake rotors are warped ? How
long is a piece of string ? Your going to have to supply
a lot more info than that.
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It sounds like the kind of question coming from someone who logged onto here looking for help , and not wanting some sarcastic Bozos wise ass comments ! He merely stated that the A/C was serviced recently, NOT that he thought it had any to do with the vibration.

(The statements below presume that your auto has late model engine management controls, not a carburetor with an idle increase solenoid.)

If you have an engine smaller that 2.5L, the engine may stumble when comming to a stop with the AC compressor running. The engine slows down and almost dies before the automatic idle control catches it. This is felt as short term shudder lasting maybe 0.3 seconds. If it continues much beyond this time, the engine may stop.

This suggests that the IACS (idle air control system) is not increasing the idle setting soon enough. The idle air bypass valve drive may be worn and stalling. Also, other parts of the idle speed control system may be faulty.

Thanks to those who are giving me advice. I'm a she and not a he and I don't know anything about cars. Thanks you so much for you help.

I can think of the following:
. engine may begin idle too low which is a semi-stall which vibrate until it catches itself and goes back to normal idle speed. This is suggested before..

. If possible open the hood and rev hard and pay attention what happens. I don't know your car type but in some older cars it might be something as simple as engine support has gone bad so you feel its normal mechanics more than normal. I owned a diesel and my vibration level was much smoother after replacing a defective support block caused by wonderful bumpy roads in NYC.

All engines vibrate more when the rpm's are down around 1000, as opposed to operating speed, 2000 to 4000 rpm. It has to do with the natural frequency of the engine block. If you think of the engine as a bell, it is a low frequency bell, and as the rpms drop, the movement of the pistons and parts connected to the pistons will begin to rock the engine. This is a normal, natural thing. It can get worse if the engine needs a tune up, and it can get worse if there is a bad engine mount. The engine is bolted to the transmission, and the transmission helps to reduce vibration at idle. A bad transmission mount can cause more vibration, too.

Kalining is correct( but too caustic) : much more info would be helpful - imagine a doctor trying to treat a patient from 1,000 even 5,000 miles away with so little information.
All the responses are good, I know that sooner or later the same may happen to me - so I read these to learn and substantiate what I already know...JemDandy has of course given the best answer,IMO, based on the least data.
I could only guess that a mount rubber has become too hard..

This is rabbit8. I have a 98 ford escort. This is something that started about 2 month ago. It's not real bad, but when I come to a stop at a traffic light, I notice a vibration. I vibrates for a few second and calm down and then maybe another few seconds. It's not a loud sound. If my hands are on the steering wheel, I can feel it vibrating. I don't know how else to explain it. I was told I might need a tune up. I'm a woman and might not be describing what I am experiencing clear enough for you to help me.

Get a tune-up (both engine and transmission (assuming it is automatic)) and have the mechanic check your motor/tranny mount.

I don't know if you found out what was causing the vibration or not.I would like to say that I have owned about 4 Ford Escorts and they all seem to do this especially when the compressor is on.I always had my cars serviced on a regular basis and nothing was ever found to be wrong.Right now I have a 1997 Ford Escort that I bought with 48k miles on it.The hood rattles when the car is idling or sitting still.I had a shop check it and couldn't find anything.It drives me nuts.

You can feel engine vibration through the steering wheel in a number of cars powered with 4 cylinder engines, especially if the Air conditioner compressor is on and the car comes to a stop. If the idle speed momentarily falls below 700 rpm, the vibration can be pronounced for 4 cylinder engines.

Rabbit, you have received some excellent answers.
Fords are inexpensive - so if they vibrate and rattle a little, well that is to be expected.
My Saab 900 does not, but look what is costs !

Any vehicle should be "tuned up" on a regular or annual schedule, with the same mechanic or shop, and records must be kept..

It is very common for '97 and up Escorts to have engine vibrations at idle and all RPM speeds due to the right front(pass. side) upper motor mount even though it looks ok. I have found this same problem (same mount location) on '96 and up SL and SC Saturn models. Hope this helps.

We have a 2006 Honda Accord. Within the first week, we heard rattling in the area of the glove compartment after the car hit a few bumps in the road. After some checking around, we put some foam weatherstripping where plastic was hitting plastic inside the glove compartment. It minimized the rattling. I think this should have been discovered as part of the dealer prep, but that's another story.

I've got a 1997 Ford Contour. I've had the same problem with my car. If I'm sitting at a light or stop sign with the car in gear and no A.C. or anything else except the engine. I noticed that if I put the car in park it doesn't do that. I've had it to Ford and other places and no one can seem to find the cause. I hope you have better luck than I have. Can't find anyone who can fix anything right these days.

Hi All,

I have hyundai sonata 1997 manual 4 cylinder 2.0L. I found similer problem with my car. When AC is on and its at idel or stop at red signal, Its start vibrating for 2-3 seconds only and then its normal for 2-3 minutes and again it start vibrating for 2-3 seconds and stop n so on.

when its start vibrating the rpm come down to 600-700 and when stopped vibrating the rpm come up to 1000.

Any suggestion would be appreciated.

I own a 99 Honda Civic and when I stop at a light or stop sign my car will vibrate if the air conditioning is running. If i turn the air off the car stops vibrating. I was wondering if anyone has any idea what it maybe.

Hello, my car stearing wheel is vibrating at idle when started cool but drives well. I just had a fuel pump put in it and there was no evidence before this pump was installed. I have bee told the mounting brackets are buldging. It's a commadore vt 2000 with 150.000 od reading, be grateful for a reply, thankyou

my car vibrates in idle position when a/c is on wit gear engaged condition