Vacuum leak testing

[Shorty62]

Hi All, I am chasing a vacuum leak in the engine bay as I've tried everything else it could be for an erratic idle. Is there any clear process you can follow to try and find it and equipment I would need to assist?

1988 3.2 litre 911 Carrera.

[HarryD]

Try spraying some carb cleaner on the hoses while the car is running. The hose that results in an engine speed change is the culprit.

[dan88911]

You find some help here.
Best way to solve vacuum leaks?

[jlex]

And if you still can't locate it by casual looking, do a smoke test on the engine. Smoke testers are pricey, but you can find a home-made smoker on fleabay or find instructions on how to build your own.

[Big Dav]

I have an 87 3.2 and ended up buying a cheapish eBay smoke tester that worked well. I pulled the vacuum line from the cruise control servo in the engine bay and introduced the smoke from there.

[Bob Kontak]

Originally Posted by HarryD

Try spraying some carb cleaner on the hoses while the car is running. The hose that results in an engine speed change is the culprit.

+1

Brake cleaner has fewer VOC's so won't ignite as quickly. On that note, I have had brake cleaner ignite from a cracked spark plug firing into the block on the back (firewall) side of a Taurus transversely mounted V6. It ain't nuttin and extinguishes quickly.

Put the red skinny tube on the tip and go to town (without being a pig). Intake runner to head mating point is a good place to focus.

Like Harry says, look for engine speed change, it can go up or down depending on location.

[steely]

Look at the air valve and rubber around it.
Do a test of the brake booster line up to the frunk.
Check out the rubber around the 'pipeline' behind the throttle body (TB).
The finer 4 / 4.5 mm lines behind the TB can dry out, it's cheap to get vac rated line and just replace these.
Check the rubber between the intake halves.
Check the torque of the intake nuts.

You can use this decal of all things vacuum as a guide - you might have this on the under side of the deck lid.

[Shorty62]

Thanks for all your assistance, I'll try and make time to give them ago - work always seems to get in the way.

[Targa Me]

Try replacing the PCV valve.
Remove the old one and shake it. If it doesn't rattle around easily, it needs replacing.
Also check the rubber adapter for cracks.

[jlex]

IAC valve

[famoroso]

Gauge test...
https://youtu.be/MRZG-s_55CU

Smoke machine...
https://www.ebay.com/itm/Automotive-EVAP-and-Vacuum-Smoke-Machine-Diagnostic-Leak-Detection-Tester/283210079548

[steve meltzer]

another way to look is with an (unlit!!) propane torch. Take your time and go over the whole engine bay. steve

[stlrj]

Originally Posted by Shorty62

... an erratic idle.
1988 3.2 litre 911 Carrera.

Can you describe the symptoms in more detail?