SR Red top Vacuum leak? dying.

SON240sx Automotive
1

Hey guys, just picked up an SR’d coupe recently.
Anyways, whenever I clutch out and am on the brakes at the same time, my rpms die and the car wants to die, and has died when I’m turning and when I come to stops and such.

when I clutch out by itself or am on the brakes by itself, the rpms die a little, but not as much as when I’m on both pedals at the same time.

Vacuum leak? dead or dirty IACV?

has Z32 front calipers if that makes any difference, OEM non-ABS brake booster and the BMC is OEM size but has been changed according to previous owner.

Thanks.

edit: drives fine otherwise

2

Check you brake booster vacuum line before anything. They tend to crack. It runs along the firewall on top. It’s easy to find.

3

hmm it seems fine from look and feel, just checked it. Everything seem tight.

4

Will it does that BECAUSE RACECAR

5

“Because racecar” isn’t a solution lol. it shouldn’t die like this, I didn’t have this issue with some other sr’d cars I’ve driven.

6

does it die off a little while you are accelerating through your gears and have to clutch out to shift up?

7

I don’t notice it really dying in between gear shifts cause I shift @ like 3k-4k rpms .
It’s when I’m slowing down and I’m on the brakes and I clutch out for example at lights or a stop sign, it drops heavily and wants to die/has died and I have to fire it back up.

When I’m off the gas and not touching any pedals, it’s fine, it doesn’t instantly drop or anything, only when I’m on either brake or clutch out or both, especially both.

8

Was the idle set properly?

9

on the SAFC unit?

Also, confirmed it doesn’t start dying in between shifts.

The problem rarely occurs anymore but still does happen sometimes. again it’s when I’m heavier on the brakes and clutch out. Boost/Vacuum gauge shows 20-22(psi?kg/2?) vacuum during idle after it warms up which I’ve been told is proper. (sorry forgot the measurement it uses)

10

are u sure it has to do anything with your clutch? so when the clutch is pressed it wants to die?

11

InHg is what engine vacuum is measured in and no the idle on the iacv.

12

Naw, don’t think it has anything to do with the clutch I was just tellin’ it like how it happens. No, when I’m heavy braking for example a red light coming off an off-ramp, I’ll slow down and when the rpms progressively drop, instead of dropping to just idle it would drop lower than that and engine would die. Still have power to everything but engine just shuts down.

Yeah, 20 InHg then. I haven’t fiddled with the IACV other than shooting some carb cleaner up one of the intake feeds hoping it would help. I’m not sure it would help to try and adjust IACV considering my idle is fine normally, when I’m not heavy braking.

13

Are you sure it’s when u brake? Cause I have a feeling u have a atmospheric blow off valve. And when u let go of the gas, and push in the clutch to brake, the blow off valve opens letting the air out that’s supposed to and is read by the maf to enter the engine. Causing it to run rich. And often die.
Is this the case!?!?!

14

nope I have recirc’d bov synchronic.

15

What rpm does your car normally idle at?

16

900-1200 rpms. ~1200rpms range when cold, settles around 900 rpms idle

17

I had the same problem with my old BOV, might be that.

18

really? cause I drove your car before you bought it. Didn’t have any of those issues.

19

that issue about the BOV only refers to one that vent to atmosphere if your is recirc then it shouldnt die, my BOV spring was slow to close back up when it was cold causing a simular issue but it was vented to atmosphere, so i just wanna be clear, only when your pressing super hard on the brake it was to die… if u get off the gas and coast its ok and when u brake lightly its fine??

sounds like to me you have a small crack in the hose connected to the Brake Master, when there is more pressure from braking hard the crack may open, just run a new fresh rubber hose and see if that fixes your issue.

20

Yes, and it’s more when I’m coming off off-ramps from ~100km/h to a full stop type of thing. No, I don’t drive like a retard and brake as late as I can, anyone that knows me and has seen me drive can attest to this.

If it’s a small crack, wouldn’t there be leaks? at least a drop? well I guess if the hypothetical crack is opening and I’m driving it would close back up when I’m parked and trying to check???