Mychal71

1999 Honda Accord LX, auto, 4cyl.

Weather you are idling in park or driving down the road, whenever we turn the air conditioning on there is a vibration that you can feel. Its been doing it for some time now. AC on, vibration, AC off, no vibration.

Any ideas?

Thanks

P_Adams

Make sure that the idle doesn't drop below 700 RPM i at idle.
Make sure the A/C Drive Belt is properly tightened and
Make sure none of the Hoses/pipes coming off the compressor are resting against anything.

Other than that and you'll need to have it road tested or looked at.

P

Mychal71

Thanks! We have to go out tomorrow so i'll see if the rpm's drop at all or below 700 once it gets warmed up. I had it looked at when I took it in to a Honda dealership for a recall replacement of the ignition switch and they told me it was bad motor mounts.

Well I replaced the motor mounts today. Left Right and Front mount. I had the rear out, but the replacement I got didnt have the vaccum canister on the bottom of it so I put the old one back in. It didnt look like it was in too bad of shape. the front and right mount were pretty worn and cracked though so it wasnt a total waste.

Anyways, I got all done, even replaced both belts because they were getting worn. Cleaned up and turned on the car, pushed the AC and STILL the vibration!!! AAAHHHHHHHHHH!!!!!

anyways, thanks for the reply! I'll let ya know what happens with the idle tomorrow.

P_Adams

It may well be the rear mount. That's the one that traditionally goes south the most. Put the car in reverse with the brakes applied and apply enough gas pedal to load the tranny in it's mount. If you've got a bad mount, it will be quite obvious.

P

Mychal71

I'll try that tomorrow too. The rear mount could be bad even if it wasnt majorly cracked? It looked a little "weather cracked" if you know what I mean when I bent it back and forth. The car has 160,000 on it and the mounts have not been replaced.

Wonder if it is that. this loading up with the brakes on will tell me if the rear mount is bad?
I was searching around and I noticed some people were saying to 'test' that mount to make sure it was working properly. How is that done?

Mychal71

Okay, put it in reverse with brake on and gave it gas as I watched the engine. The back of the engine (above the rear mount) lifted up and tilted towards the car pretty good.

The idle did not lower when I turned the AC on. But it did raise to about 1000rpm then drop back down to what I would gues is around 750 or so.

Something that I did notice is that it actually vibrates alot when the fans kick on. Even if the ac isnt turned on. You feel it alot more when it is at idle in park. You still feel it in drive but not as much as in park.

So its not necessarily when the ac is turned on or off, but more when the fans kick on.

Elvis1977

I chased a vibration problem for months before I solved it on my 98 accord 4-cyl. I changed the front motor mount and rear motor mounts with factory Honda parts only and the vibration improved. Do you feel vibration when engine is in drive, but car not moving? Or, vibration increases when temperature outside gets cold? Vibration will also increase when you turn on your headlights. I would change that rear motor mount with honda factory part.

Mychal71

well I was almost sure it was the fans up front. One looks like its off balance a little and has been clicking once it shuts off. I unplugged each fan one at a time and with one or both unplugged with the a/c on, it still vibrates. So it is not the fans.

So the only thing left would be something to do with the ac compressor itself or the rear mount, which is the only mount I have not replaced yet.

I am gonna search for a way to test the rear mount and see what happens.

I did take a vacuum reading with the car warmed up and at regular idle (just below 1000, probably around 800 or so. I unplugged the vauum line where it comes out of the little distribution block and that port reads 18psi. not sure if that is good or bad, but I'll keep searching.

SPLIT2NDEJ8

car shakes when a/c on, i use lucas fuel injection cleaer right before i pump gas. then it stop. when a/c is on it takes more power more fuel. buy it from autozone then after tell me if it worked for you. because i been using it to half my cars and it always worked.

alkoholikwun

idle should drop when a/c is on, should be normal unless its shaking violently. my idle drops a few hundred rpm, but it still idles good with a/c on. thought this was normal?