Vacuum Leaks - Where?

[bcrdukes]

Hi guys,

My DME threw the infamous code 1222. My suspicion is a vacuum leak however, I don't even know where to start. Contrary to popular belief, it's not the oxygen sensor, however, it's been replaced because it was definitely time for replacement, as with my fuel pump. My fuses and relays have been extensively tested and swapped from a good, known E30 325i M20 as well. The car needed maintenance so I've replaced the spark plugs, timing belt, water pump, and distributor.

I started looking at some obvious places however, so far I have looked at:

1. Throttle body/charcoal canister (that funny elephant trunk/tube)
2. Air intake boot (I've swapped maybe 3 known good ones)
3. Valve cover (changed the gasket which was due anyway)
4. All hoses visually look fine with not cracks visible
5. Swapped 3 AFMs

Where else can I look for a vacuum leak? One can never be too sure about what I've already checked so I am open to any suggestions.

I find it difficult to start the car when cold. We all learned in grade 4 science that materials expand when things get hot, so my hard-start issue is rampant when the car is cold or has cooled down after a drive. I find it hard to rev match when I'm driving because it feels as if some quantity (if not, a lot) of air is being unmetered and I can't get the flywheel to match the desired RPM/speed interval.

Any leads, guys? I've heard people mention the oil dipstick being a culprit? Thanks!

[SpecM]

Intake manifold gasket and/or injector o-rings can leak air too

[ben312]

take a can of carb cleaner or water in a mist bottle, spray over all your lines, if you see bubbles or the idle dips or spikes you have found your leak point

[jlevie]

The best way to find intake leaks is to have a smoke test run on the intake and crankcase. The possible intake leak locations on an M20 engine are:

Intake boot
Crank case breather hose
FPR vacuum line
Valve cover gaskets
Oil filler cap seal
Dip stick o-rings
Intake manifold gaskets
Throttle body gasket
Injector seals
Oil return tube seals
Brake booster and lines
Evap control valve
ICV connections

[bcrdukes]

Intake manifold gasket and/or injector o-rings can leak air too

I was afraid of this. Total PITA I don't want to deal with.

[nickpdx]

Try spraying carb cleaner all over any possible vacuum leak locations as mentioned. Though, I went through nearly a whole can trying to find a vacuum leak in my car this summer...never found it, only went away after I replaced the intake manifold/throttle body gaskets and put new o-rings on the oil return tube.

[jlevie]

Spraying carb cleaner on suspect areas only works if you can hit the leak with the fluid. A smoke test works regardless of where the leak is.

[gw ix]

Never spray carb cleaner anywhere to find an intake leak, I watched a guy burn a 10 second $60K supra to the ground doing this. Once the fire started he didn't even have time to get to the fire extinguisher mounted on the roll cage.