Idle Speed drops when AC is turned on??

[orchard2]

Hi, I'm new here.

We just got a 1999 beetle. When the AC compressor is turned on, the idle drops and the engine shakes alot. Driving is fine, but when coming to a stop....it's not. I know the car is supposed to compensate air value's when the AC is turned on, I don't think it's doing it.

So, how to figure it out? Can I just raise the Idle? How do you raise it?? Is there a "how to" site where someone has these things?

[MyOtherRidesAVette]

It has always been normal for an engine rpm to drop slightly when loaded with the a/c compressor being added to the mix. The shaking, not so... At what rpm is the engine idling when the a/c if off? Don't have a clue as to how to adjust this, I would think with all the electronics this is an automatic adjustment on the NB, but IDK.

MORAV

[orchard2]

The car idles at 800 or so, normally.. But when you turn on the AC, it,s dropping it down to like 450rpm. Is there a control valve that should open when the AC is turned on? If so, where?

[MyOtherRidesAVette]

I think that is a substantial drop in rpm, more than it should be, but maybe not. I don't know if there is a computer that should compensate for the compressor or not. The clutch could be trying to seize or dragging. Any stronger noise coming from the compressor than normal. And I'm sorry, a control valve for what?

[Toad]

That is rather fishy. The idle can drop, but only down to like 700-750 or so.

depending on the mileage you have
Do you know the last time the spark plugs were changed?
Are all the vacuum lines good?
Has the throttle body ever been cleaned?
How old is the fuel filter?

This sounds to me like you need a tune up.

[billymade]

I noticed the last time my coil packs were swapped for the latest revision under the warranty recall; that my beetle seemed much less affected by the a/c being on (still affects power but it used to be way worse 1.8T).... just thought I would mention that...; with such a drop in rpm, I wonder if the compressor is failing and is causing a big drag (load) on the engine. Something is definitely, not right; what do the belts and compressor sound like when the clutch engages?

[MyOtherRidesAVette]

POST #4

Originally Posted by MyOtherRidesAVette

I think that is a substantial drop in rpm, more than it should be, but maybe not. The clutch could be trying to seize or dragging. Any stronger noise coming from the compressor than normal.

POST #6

Originally Posted by billymade

with such a drop in rpm, I wonder if the compressor is failing and is causing a big drag (load) on the engine. Something is definitely, not right; what do the belts and compressor sound like when the clutch engages?

One can only marvel at the redundancy of posts on threads around here, or why ppl feel the need to do so! I have one regular poster who seems to follow me around affirming my posts almost daily. Perhaps I should be flattered? Typically when I agree with another poster, I'll simply quote them and give it a x2, x100, Ditto... and then add any additional thoughts or information. More respectful to that poster, it doesn't appear as if I'm treating them like they are not there.

M.

[orchard2]

Funny, I know what youn mean. From reading these forums, most techs are saying the obvious.. Nothing like the Porsche forums, those guys know cars.. Is there a PDF parts catalog that I can download somewhere??

[MyOtherRidesAVette]

Originally Posted by orchard2

Funny, I know what youn mean. From reading these forums, most techs are saying the obvious.. Nothing like the Porsche forums, those guys know cars.. Is there a PDF parts catalog that I can download somewhere??

Ditto the Corvette forums... Different mindset, here, but still a great forum for what it is (as much as social network as anything else). But, there are very NB knowledgeable ppl here. I think I have some information on your request, somewhere. I'll put it on my to do list, and send you a p/m in that re when I have time to dig it up.

M.

[orchard2]

Yeap, still a great forum. Thanks man. And yes, those Corvette guys don't mess around either.. The LS series of motors are hands down the best for making power.. I dream one day of building an LS7 powered Porsche 928, oh yeahhhh