Do I Have A Vacuum Leak? Or Am I On The Wrong Track?

[my94coupe]

Hey Guys,

I am more or a reader than a poster but i have come seeking advice.

I have what i believe to be, is a substantial vacuum leak in my 1994 S1 R33 Gts-t RB25det 4 spd Auto,

I say believe because at the moment, i am struggling to locate the problem,
Being of a non-mechanical background, i can only say that believe i have a substantial vacuum leak, because all the indications point to that at this stage such as:

- low rpm stalling, (4spd auto)
- stall at idle,
- stall when braking at slow speeds etc when the engine is at operating temperature.
- I have to switch the engine compeletely off, count to five and it will fire again no issues
- a softer brake pedal

My initial research lead me to the IAA/IAC valve at the back of the stock intake manifold so i had it looked at, and a new gasket fitted, but the problem remains, now even more significantly since they worked on it. The little coupe has become undriveable.

Can anyone shed some light on this?

Has anyone had similar experiances?

I have had my coupe for 15 years and never had an issue, this is the first time it ever given me grief.

If it is Vacuum, then i guess it is replace every associated gasket and hose on the left side of the engine until it is located?

Modifications to consider:

Cold air induction

FMIC.

Other that than that the Engine is utterly stock.

Attached are the most recent photos of my twin cam, merely for reference, however note that the blow-by hoses 2 and 3 and now NisGen parts.

Cheers Guys,

Regards

Jeff

[shakows]

Did you clean out the IAC when the gasket was replaced?

The AFM Solder issue is also quite common

Do you have BOV that vents to Atmo?

"stall when braking at slow speeds etc when the engine is at operating temperature."

I have this issue on my 1994 R33 S1.5 Manual and from what I've been told this is a common issue due the BOV

[my94coupe]

Did you clean out the IAC when the gasket was replaced?

The AFM Solder issue is also quite common

Do you have BOV that vents to Atmo?

"stall when braking at slow speeds etc when the engine is at operating temperature."

I have this issue on my 1994 R33 S1.5 Manual and from what I've been told this is a common issue due the BOV

Hi Ben,

The instructions given to the workshop were to remove, clean and replace the IAC with the new gasket.

The new gasket is clearly visible and i was assured that the valved was cleaned....without removing it, i am guessing there is no way to check the work.

I hadn't thought of the AFM sensor, i will chase that up, much appreciated, thank you.

The blow off valve is factory standard, did you mean after fitting an aftermarket one? or with aged stock ones?

Thanks for the reply mate,

Cheers,

[Hadouken]

Is the idle higher?

It's very easy to check AAC. As in super easy. I don't see how they could clean it without removing it. Unless they put upper engine cleaner through the car.

[my94coupe]

Is the idle higher?

It's very easy to check AAC. As in super easy. I don't see how they could clean it without removing it. Unless they put upper engine cleaner through the car.

G'Day Mate,

The idle all good, it was a little high when i got it back from the workshop, but has settled down now. Should i look for something in relation to that?

I had been tempted a couple of times to remove it and check, i have a spare gasket, and given that the gasket is new, it maybe safe to remove and inspect.

But like i said, i am non-mechanical. By your comment of "very easy to check AAC. As in super easy" inspires me to maybe give it a go.

Thanks mate,

[Hadouken]

Look up the diy man. It takes you through it all.

[my94coupe]

Look up the diy man. It takes you through it all.

I'll do that, thanks Hadouken,

[89CAL]

Is your BOV return going anywhere? Im looking on my phone so the pictures dont come up great, but looks like it is either blanked or not going to the hardpipe

Im happy to be wrong. Just looks a bit like that

[my94coupe]

Hey Mate,

For sure, i have attached photos taken tonight,

Cheers

[89CAL]

Too easy

[tridentt150v]

Does it go ok when you are driving at say 80-100kph?

Check all your hoses to the intercooler etc, also check your hose clamps.

[blind_elk]

There appears to be a kink in the hose from the exhaust rocker cover vent down to the turbo. Maybe take care of that before you try anything else.

[Ben C34]

There appears to be a kink in the hose from the exhaust rocker cover vent down to the turbo. Maybe take care of that before you try anything else.

In the first post he says that's sorted.

[my94coupe]

Hey you lot.

So a month or two down the track,

turns out there were two issues, not one.

The IAC/AAC was the issue with the low speed stalling.

Turns out the mechanic did FA when it came to the resto on it.

I took it off my self as suggested above and sure as sh1te nothing had been done at all, he had simply replaced the gasket.

An hour or so later and a bucket load of carbie cleaner sorted out the low rpm stalling.

But, it did not address the other issues, so now it will hesitate, jerk hard, stutter then it will simply lose all electrical power for a few seconds, then stall.
This can happen at speeds between 40-110km/hr, and it is getting very dangerous.
No warning lights appear on the dash at all (i.e the engine warning light) until it stalls, then all the dash lights come on as it would if i turned the key one past acc.
After pulling off to the side, i need to then switch the engine all the way off, count to five, then it will fire instantly.
One of two things will then happen, either it will fire up and continue without issue, or, immediately repeat itself 5, 6, 7 times until it "clears" and I can get home.
Further to note, it can be either at cruising or under acceleration, but not as i slow.

So I am still chasing bugs.

What i have done so far:

cleaned the throttle body,

cleaned the AFM sensor

CRC'd every electrical connector i could find,

checked every coil pack,

checked every spark plug

cleaned my K&N pod with recommended cleaner,

But still it persists,

Any guidance would be well received!

Any suggestions or similar experiences?

Cheers guys,

[Hadouken]

Solder afms

Unplug o2 sensors

Report back

[breaker1845]

Check your ECCS loom is connecting to the main loom properly. Been in a car that had a similar problem and it was because the ECCS loom was not connected to the main loom properly, it came loose somehow. It's the plug which is grey in colour and sits near your coolant bleed plug and fuel rail, quite easy to spot.