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General E46 Forum
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Old 04-12-2012, 04:29 PM   #21
ac_2007
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Old 04-12-2012, 04:52 PM   #22
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this is completely normal
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Old 04-12-2012, 05:06 PM   #23
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You must not have comprehended a single post in this thread.
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Old 04-12-2012, 05:23 PM   #24
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Stupid question, but to those that have this problem (and it's not VANOS or otherwise diagnosed), are your cars manual or slushbox?

Do you get this drop in revs when the clutch is depressed? (I couldn't tell from the OP description of "shifting gears" if he had a manual and if so where in the shifting gears this occurred). Even at idle does putting the clutch in do anything?

Give the car WOT at idle or while driving (maybe easier while driving) and do you get any hiccups then? Cause I know there's a relay on most modern cars that shunts the a/c compressor when at or near WOT. Interested to know if that's functional or failing or goofy.

And have you had your cars pulled for codes, not necessarily SES/MIL lamp triggering codes? There's got to be some info there.

Last edited by ChicagoRY; 04-12-2012 at 05:24 PM.
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Old 04-12-2012, 05:33 PM   #25
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I have no codes, and I drive a manual.

Was wondering if there is a connection from the HVAC/AC that tells the DME it is on. That way, it can compensate throttle position to maintain smooth driving.
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Old 04-12-2012, 05:40 PM   #26
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I would think it would be possible that the A/C compressor is messed up in a way that would cause more parasitic drag on the engine than normal and therefore resulting the the near stalling situation.
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Old 04-12-2012, 05:51 PM   #27
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I never found out the problem but after I did the VCG it hasn't done it since. I'm waiting for it to come back again
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Old 04-12-2012, 05:55 PM   #28
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I have no codes, and I drive a manual.

Was wondering if there is a connection from the HVAC/AC that tells the DME it is on. That way, it can compensate throttle position to maintain smooth driving.
I'd be real interested to hear what happens with the engine clutch in during driving and at idle, as well as what happens during WOT.

And AFAIK there is no real time variable correction, only a WOT cut out because it knows you want or need full engine power then. And though I say WOT cut out, different vehicles cut out at different amounts of throttle, though it's referred to as WOT a/c cut off (at least by the meat head Chevrolet owners I started off my automobile gang membership with in the mid to late 1990s ).
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Old 04-12-2012, 06:37 PM   #29
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Mine started doing this about a week before the a/c compressor failed and sent black death throughout my a/c system. Does your a/c also take a little while to kick on when the engine is first started, and cut out at weird times?

Those were all the symptoms mine had. Idle control components wouldn't have any impact on how quickly the rpms drop, only if they are allowed to drop past a certain point. If the engine rpm is dropping dramatically when shifting with the a/c on, the only thing I would think of is that the a/c compressor is causing too much drag.

Good luck,
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Old 04-12-2012, 06:52 PM   #30
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^ That's what I'm thinking. Perhaps the bearings are shot, or it is an aftermarket replacement not well suited for this car.
Only past maintenance I've done is recharge it.

The compressor works fine the few times I use it, doesn't cut out and kicks in almost instantly.
Seems I need an A/C specialist..
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Old 04-12-2012, 08:46 PM   #31
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^ That's what I'm thinking. Perhaps the bearings are shot, or it is an aftermarket replacement not well suited for this car.
Only past maintenance I've done is recharge it.

The compressor works fine the few times I use it, doesn't cut out and kicks in almost instantly.
Seems I need an A/C specialist..
I think these guys have more likely ideas than my own.

Compressor and/or compressor clutch are not uncommon failure items on any car. High wear and tear item, and r-134a (and most refrigerants) are solvents and will naturally wear away at seals over time, and also when your a/c is refilled they also usually put in some compressor oil with it, but it's real easy to mess up the balance of compressor oil to refrigerant to the detriment of the compressor.
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Old 04-13-2012, 08:32 AM   #32
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That vanos looks like a very LONG DIY
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Old 04-13-2012, 12:29 PM   #33
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^ LOL, irl
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Old 04-15-2012, 06:36 AM   #34
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If you look at the description for failing Vanos seals, engine speed surge while shifting with the A/C is one of the signs. If the car has never had the Vanos serviced, maybe it's about that time to do so. I'm going to be replacing my VCG and Vanos seals pretty soon. I get an idle surge and what seems like the Vanos rattle, especially when turning the wheel.
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