vibration at idle with ac on

[834dr]

I've got a plain ole 3.8l V6. Got the car from an old lady. Blown radiator, motor mount, and lot's of other parts I've replaced. Car hasn't been registered since 97. I've replaced everything I know how to do and she runs pretty darn good. Still have some work to do but for 900 bucs for the car with a mint interior and almost decent exterior, is a pretty good deal.

Now I here's the problem. When I'm at a light with the ac on, It vibrates pretty bad. AC off, no problem. I had the AC system converted but it did it before that anyway. Now I'm used to wrenching on engines without computers and solenoids, and this thing as more emissions and sensors than I'm used too.

Is it the ICS not raising the idle when the ac cuts on? I can put it in nuetral or park and it slightly vibrates or I can hit the brake with my left foot and raise the rpms with my right foot. So to me it's an idle thing.

But could it be a bad Idle contol Solenoid or something with the AC not sending electrical signal to the ICS to up the rpm?

Any help would be appreciated.

 

[wickedtt]

I've got a plain ole 3.8l V6. Got the car from an old lady. Blown radiator, motor mount, and lot's of other parts I've replaced. Car hasn't been registered since 97. I've replaced everything I know how to do and she runs pretty darn good. Still have some work to do but for 900 bucs for the car with a mint interior and almost decent exterior, is a pretty good deal.

Now I here's the problem. When I'm at a light with the ac on, It vibrates pretty bad. AC off, no problem. I had the AC system converted but it did it before that anyway. Now I'm used to wrenching on engines without computers and solenoids, and this thing as more emissions and sensors than I'm used too.

Is it the ICS not raising the idle when the ac cuts on? I can put it in nuetral or park and it slightly vibrates or I can hit the brake with my left foot and raise the rpms with my right foot. So to me it's an idle thing.

But could it be a bad Idle contol Solenoid or something with the AC not sending electrical signal to the ICS to up the rpm?

Any help would be appreciated.

It's a loose bolt on the a/c compressor check them all but the one that usual is the front at the 7 o'clock postion

 

[834dr]

I'll check em again. Are you talking about a compressor housing bolt or a bracket bolt?

 

[834dr]

But there is no vibration at higher rpms?

 

[wickedtt]

the housing..

 

[Junior Samples]

What about a defective AC clutch control relay? wouldnt that cause the rough idle that he describes? with AC on at Idle not sending message to IAC

 

[834dr]

Wouldn't the compressor clutch not engage at all if the relay was bad?
I'm going to go through it today.

The solenoid I'm talking about is the Idle speed conrol solenoid on the side of the carb.

 

[TURBOV6]

I might have the same problem. I will try to change to a shorter belt

 

[QUIP'6']

I've got a plain ole 3.8l V6. Got the car from an old lady. Blown radiator, motor mount, and lot's of other parts I've replaced. Car hasn't been registered since 97. I've replaced everything I know how to do and she runs pretty darn good. Still have some work to do but for 900 bucs for the car with a mint interior and almost decent exterior, is a pretty good deal.

Now I here's the problem. When I'm at a light with the ac on, It vibrates pretty bad. AC off, no problem. I had the AC system converted but it did it before that anyway. Now I'm used to wrenching on engines without computers and solenoids, and this thing as more emissions and sensors than I'm used too.

Is it the ICS not raising the idle when the ac cuts on? I can put it in nuetral or park and it slightly vibrates or I can hit the brake with my left foot and raise the rpms with my right foot. So to me it's an idle thing.

But could it be a bad Idle contol Solenoid or something with the AC not sending electrical signal to the ICS to up the rpm?

Any help would be appreciated.

mine does the same thing it will actually make the turbo cover sound like someone took a screwdriver to the alternator fan. this noise was driving me crazy. with the ac off it is fine i noticed when i rev it and it comes to an idle the ac makes a groaning noise. so it turns out the ac bearing is going out

 

[834dr]

The only thing that gets me is that is did the same thing before and after the compressor was replaced.
I had a remanufactured one put in when it was coverted to 134a. Yet is still does the same thing.
Maybe I'll just take it in the shop. AC systems aren't my thing

 

[TURBOV6]

Another thing it can be is too much freon in the system putting a bigger load on the a/c clutch.

 

[jamier]

similar problem

I also have a similar problem with my 2000 s-10 at idle in park the truck is nice and quiet same when im driving but as soon as i put it in gear I get a rattling sound that i was sure was a loose exhaust system. the noise goes away as soon as I turn the ac-or heater to the off position. I had gm check it out thinking the compressor was faulty but they said all was ok. Im also out of ideas on this 1. but for the record the ac in my t-type is fine .........

 

[QUIP'6']

do you have a torque strap if so maybe it is to tight they do transfer vibrations

 

[TURBOV6]

Problem fixed!

The shorter belt fixed the problem.

 

[Turbo1dr]

The cause of that type of vibration is the a/c belt flapping back and forth. I've seen it soooo many times back in the 80s with customers cars. It would only do it at an idle with the a/c on. When the belt starts to flap it would transfer the vibration through the a/c hoses and to the evaporator case. That would make the noise be amplified and the passengers would hear and feel it.

Glad the shorter belt fixed the problem. The next time it does it again look at the a/c belt as it comes back up from the crank pulley to the a/c pulley. That's where it would flap.

EDIT: This post was intended for the original poster with the NA 3.8L car.