Smoke testing for vacuum leak in turbo engine.

[atikovi]

I have a 2013 Fiat Abarth that is constantly throwing a P2172 for vacuum leak detected. I've smoke tested it 3 times with a conventional smoke machine and found no leaks. Think I did it correctly by putting the smoke into the duct that goes to the turbo after the air filter, but I didn't block the tail pipes since there shouldn't be direct air flow there.

Smoke machines use low pressure, like 1/2 psi but turbos make 10-15 psi. Do I need a tool that will test at high pressures? I saw Lisle makes this: https://www.lislecorp.com/specialty-tools/69910---turbo-air-system-test-kit-wsmoke-adapter-14pc

 

[toplessHO]

block off intake,exhaust and any vents in fuel tank
apply smoke and see where it comes out.
the leak may not be external ,example vacuum leaking into exhaust.

 

[OneDollarSaab]

Yeah internal leaks like the brake booster can be a cause. Verify the functionality of any check valves after the throttle body.

 

[atikovi]

Yeah internal leaks like the brake booster can be a cause.

But wouldn't I see smoke from the booster if it was leaking?

 

[Steve_P]

Turbo owners do pressure tests. 15 PSI or more. Do a Google search.

 

[2ndGearRubber]

What are the fuel trims at idle, and 2500?

 

[atikovi]

What are the fuel trims at idle, and 2500?

I'll check.

 

[OneDollarSaab]

But wouldn't I see smoke from the booster if it was leaking?

There's a diaphragm inside the booster, you may not see the smoke at all

 

[atikovi]

There's a diaphragm inside the booster, you may not see the smoke at all

But then it's not a vacuum leak if the booster isn't open to the atmosphere?

 

[2ndGearRubber]

But then it's not a vacuum leak if the booster isn't open to the atmosphere?

If the booster is under vacuum on both sides of the diaphragm, you can draw in unmetered air. Typically a small tear is what does it, and sometimes the leak will only be present when pressing the pedal.

 

[toplessHO]

pulling the supply to vacuum booster and capping off will tell if its that tho

 

[atikovi]

pulling the supply to vacuum booster and capping off will tell if its that tho

Do you mean remove the hose and cap it, THEN smoke test it?

 

[Roju1985]

Do you mean remove the hose and cap it, THEN smoke test it?

I was thinking he was saying bypass the booster and see if it runs better.

 

[rlitman]

But wouldn't I see smoke ...

You will not see smoke from an internal leak.

 

[atikovi]

I was thinking he was saying bypass the booster and see if it runs better.

So drive around with nearly no brakes? It runs just fine until the code sets and it goes into limp mode. Can I just test the booster to see if it holds vacuum?

 

[2ndGearRubber]

No, just block the vacuum line at idle and see if the trims change.

Again, in global obd2 data, fuel trim short and long term at idle and 2500+rpm. If trims improve you likely have a vacuum leak issue, if it doesn't you have a metering or supply issue.

Randomly checking parts isnt going to find your problem.

 

[2ndGearRubber]

Electronic throttle actuator and map actual values are compared to calculated values. If they differ beyond X percent, p2172 sets.

 

[Wrench97]

Are you running a stock Throttle valve or a performance aftermarket unit?

If you smoked it and do not see a leak I'd be looking at the map sensor reading while driving or watching the TPS sensor on the scan tool for drop outs.

 

[atikovi]

No, just block the vacuum line at idle and see if the trims change.

Again, in global obd2 data, fuel trim short and long term at idle and 2500+rpm. If trims improve you likely have a vacuum leak issue, if it doesn't you have a metering or supply issue.

Randomly checking parts isnt going to find your problem.

Here is a video of live data at idle and 2500 rpm with vacuum line connected:

 

[Wrench97]

6 PSI manifold pressure at idle and 3PSI @2500?

Where you driving it or just revving it up?

Again is this a stock setup or aftermarket parts are involved?

 

[atikovi]

I was just sitting in the driveway. And a vacuum gauge reads about 21 inches at idle.

 

[Wrench97]

Vacuum gauge says vacuum and map sensor says pressure, I would check the wiring to the map(IE unplug it while looking at the scan tool and note what if any change their is) if it looks ok, change the map. The readings change so chances are the wiring is ok.

 

[atikovi]

MAP sensor is new Bosch oem and I tested wiring from MAP to ECM and all wires under 1 ohm.

 

[quattroman]

I pressure test to peak boost pressure, I have had a couple of weird leaks that only seemed to open up at higher pressures.

 

[p00p]

Evap valve is suspect. Do your smoke test and after the smoke is fed, remove the fuel cap checking for smoke.

 

[99LeCouch]

Torn wastegate diaphragm? That could cause a vacuum leak.

 

[Wrench97]

What does the scan tool read with the map unplugged?

 

[atikovi]

Will check that and the others mentioned tomorrow, thanks.

 

[2ndGearRubber]

Here is a video of live data at idle and 2500 rpm with vacuum line connected:

Fuel trims say no vacuum leaks, now anyways. You're averaging +/- 5% or so. As others mentioned the purge could be sticking open.


Does it make full boost pressure wide open throttle driving down the road? That'll tell you if it's an issue with actually loosing/leaking pressure, or an issue with the throttle. Can you compare a boost pressure sensor against the MAP value for a sanity check of both?

 

[atikovi]

So far, smoke tested again, no smoke from gas filler. Makes plenty of boost, over 12 psi on the gauge, but haven't been wide open yet.