My vent air flow drops off when I'm accelerating ?

[Highmilagecutlass]

Ok heres the poop.

 

I suspect a vacume leak some where..please help..I checked everying under the hood including the ball with carb cleaner and did not notice any change in my idle:(

[WhatTheFehl]

What do you mean by "air flow drops off" ? Does it change temperature? is there a different rate of flow?

[jake91]

if your talking about a/c thats normal it shuts off or dips down while accelerating

[birdman]

my lumina did this, any time i was hard on the gas the air flow out of the vents dropped to near zero. i believe its incentive to stay off the gas because its not going to go anywhere fast anyway

[pontiacmaniac94]

Yah, basically, I would be really worried. probably about time to torch the car.

 

but in all seriousness, The A/C will do that when accelerating, because the car has zero power to begin with, and when the a/c is on, it has negative Hp, so to compensate for that, the blowers turn off so the car isn't even slower than normal.

 

Some cars when you do that, you lose the cold air, but still blows just as hard.

[oscar_wilde]

Hilarious jokes aside...

I think the loss of air flow you are feeling is probably the vents switching from whatever you have selected to the default, defrost.

The check valve in the vacuum line or actuator itself probably died. The actuator is powered by vacuum created by the engine. When you accelerate, decelerate, anything but cruise, you get inconsistent vacuum levels. When the vacuum, for whatever reason, is disrupted, the vents will go to defrost as a sort of safety system.

[AL]

Maybe the vacuum ball by the left front wheel got disconnected

[jman093]

Hilarious jokes aside...

I think the loss of air flow you are feeling is probably the vents switching from whatever you have selected to the default, defrost.

The check valve in the vacuum line or actuator itself probably died. The actuator is powered by vacuum created by the engine. When you accelerate, decelerate, anything but cruise, you get inconsistent vacuum levels. When the vacuum, for whatever reason, is disrupted, the vents will go to defrost as a sort of safety system.

 

x2. The compressor only shuts off pretty close to WOT and that won't affect airflow.

[IRONDOG442]

NO THESE CARS ARE DESIGNED TO DO THIS, ITS OK! READ YOUR FSM !! HE PROBABLY HAS ECC!

[Highmilagecutlass]

if your talking about a/c thats normal it shuts off or dips down while accelerating

 

Thanks Jake ! It only does that when the a/c is on, and know that makes sence:)

[kevins93z34]

I just went through this same problem on my 93 Z34. pull the battery and inspect all the vacuum lines under it including the hard plastic line that runs to the ORB OF POWER :willynilly:under the front of the car. I had a hole in my line and splicing in a piece of rubber vacuum line solved it.

 

You probably won't see any vacuum there even at idle because the ORB OF POWER:willynilly: doesn't have anything going into it. When you are under heavy throttle the check valve closes off vacuum supply from the engine and allows things like the HVAC and cruise to pull vacuum from the ORB OF POWER:willynilly:. That way you don't lose airflow or cruise. When the check valve has enough engine vacuum applied to it such as at idle or while cruising, it closes off the port to the ORB OF POWER:willynilly: and allows engine vacuum to run those things, until you floor it again and then the cycle repeats.

 

Make sure the ORB OF POWER:willynilly: isn't damaged and also while checking your lines check or replace the check valve, it can be found in the HELP! section of most auto stores; I know autozone has it for a few bucks.

[jake91]

Thanks Jake ! It only does that when the a/c is on, and know that makes sence:)

 

yeah mine starts noticeably kicking out at around 3k and normaly shifts to floor bloiwng warm air this is mainly a safty for the compressor because they dont like high rpms

[Highmilagecutlass]

I just went through this same problem on my 93 Z34. pull the battery and inspect all the vacuum lines under it including the hard plastic line that runs to the ORB OF POWER :willynilly:under the front of the car. I had a hole in my line and splicing in a piece of rubber vacuum line solved it.

 

You probably won't see any vacuum there even at idle because the ORB OF POWER:willynilly: doesn't have anything going into it. When you are under heavy throttle the check valve closes off vacuum supply from the engine and allows things like the HVAC and cruise to pull vacuum from the ORB OF POWER:willynilly:. That way you don't lose airflow or cruise. When the check valve has enough engine vacuum applied to it such as at idle or while cruising, it closes off the port to the ORB OF POWER:willynilly: and allows engine vacuum to run those things, until you floor it again and then the cycle repeats.

 

Make sure the ORB OF POWER:willynilly: isn't damaged and also while checking your lines check or replace the check valve, it can be found in the HELP! section of most auto stores; I know autozone has it for a few bucks.

 

Thanks Kevin I will check that out ! is the check valve near the the vacume tee below the battery ?

[carkhz316]

x2. The compressor only shuts off pretty close to WOT and that won't affect airflow.

Yep. And it's not for the sake of the compressor, its actually for the engine really to free up the ponies. Jake, if yours is kicking out at moderate throttle and changing vent positions, it's not normal and you more than likely have a similar issue to OP's

[Galaxie500XL]

I've had similar experiences...be sure to check the Orb Of Power.

 

 

Do you realize the acronym for that is OOP?

 

[Crazy K]

I read this thread and then I LOLed it is NOT normal.

 

A complete loss of vacuum would be apparent as a total loss of HVAC selection control, and on cars so equipped (93- and 94 lumina) vacuum operated Cruise control.

 

A partial loss of vacuum would be apparent under higher engine demand conditions. You have a small leak and when the engine stops producing vacuum during demand, the OOP (aka vacuum ball, aka vacuum reservoir) looses it's vacuum supply and functions stop working.

 

below the master cylinder along the drivers' side body rail is the check valve and T for the system, and from there forward going under the battery is the line that goes to the vacuum ball. those are the areas where failures can occur. inspect, seal and replace anything you find wrong.

[Highmilagecutlass]

I've had similar experiences...be sure to check the Orb Of Power.

 

 

Do you realize the acronym for that is OOP?

 

lma0:lol:

[Highmilagecutlass]

Thanks..I will take a peek tomorrow ! I suspected something in that area after reading some threads here ( man I love this site )

 

I will do a visual inspection with the engine off then listen for leaks..I tried spraying all of those connections with carb cleaner and listening for a change in the idle. But I'm not sure if that vacuum source can be checked that way . Maybe just a visual inspection looking for cracked lines or dry rot..

[Crazy K]

i do not think the carb spray method will work on the those lines since there flow so little and are so small and far from the engine... I'd grab and wiggle them instead.

[White93z34]

I'd love to know what gives with this issue as well. My z34 has a properly functioning vacuum ball, and cruise, hvac it all works fine. But my vents will drop out at the slightest upward grade I have to traverse and under most any load condition.

 

my G/Fs euro 3.4 does not do this, and the line feeding the vacuum ball on her car is blocked off cause i broke it a long while back.

[kevins93z34]

it fills me with glee that ORB OF POWER has become a common in use phrase in this thread lol

[Crazy K]

Chris, I suggest you replace the check valve. it has probably failed internally.

[chrisflstf]

Anybody have a P/N for the check valve? I have exactly the same issue with my car - 96 Regal GS. I lose most of the AC air flow under a load.

[mfewtrail]

Anybody have a P/N for the check valve? I have exactly the same issue with my car - 96 Regal GS. I lose most of the AC air flow under a load.

 

Go to the "HELP!" rack/aisle at any parts store and grab part # 47150. If you want an original check valve from the dealer, I can probably get you a part # for that as well. I've been using the HELP! ones a few years now without an issue for what it's worth.

[Crazy K]

Go to the "HELP!" rack/aisle at any parts store and grab part # 47150. If you want an original check valve from the dealer, I can probably get you a part # for that as well. I've been using the HELP! ones a few years now without an issue for what it's worth.

 

WAIT! the newer cars use a different valve than the older cars. I've seen a "Help" part that appears to be the same as the older cars, but not the newer cars...