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Discussion Starter · #1 ·
13 Abarth Cab with a stick, and 76k miles. Took the air box off and found this hose flopping around. I saw two ports near the Throttle body, both of which were capped off. The one closest to the TB seemed to have a permanent cap, but the other appeared to just be a rubber cap. Based on an image search of under hood photos, I made the educated guess to remove the rubber cap and connect the hose, as it appeared that was where other people had this hose connected.

I’m curious what that hose is, what it’s connecting, and any ideas why someone would have unhooked it and capped the nipple? The hose was just left flopping around with no plug or anything.

I had the air box off troubleshooting an intermittent P2172 and was looking for evidence of cracked hoses or vacuum leaks.
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That's a return hose for PCV, and that's the right place to plug in. I'm really curious why that was off. Maybe it had a catch can?
P2172 has kind of many causes, and you kind of have to track them down one by one. Vacuum leak is the first place I'd check, so I think you are on the right track.
 

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Discussion Starter · #4 ·
I’m also now getting stalls and throws a P0106, which is making me suspect faulty sensor or wiring for the MAP. Fires right back up and drives fine afterwards lol.
 

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Discussion Starter · #6 ·
(post got messed up...I'll try to re write it later)
Thanks mate. I'm looking forward to any input you may have.

So I'm beginning to suspect the car was modified and then returned to stock - I asssume an aftermarket intake or airbox may account for that PCV return being capped off if the aftermarket unit didn't have the plumbing for it. Got an appointment with a Fiat tech next month for those two symptoms, as I don't see any evident vacuum leaks and I'm hesitant to throw parts at the problem. Will see what they say.
 

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Discussion Starter · #7 ·
Lots of new info on this.

Dealer had the car for ~4 months. Replaced MAP and TB. Car hasn't stalled since then, but still does P2172 & limp mode. Shut off/restart the car runs fine afterwards. This tells me the issue was a combination of multiple factors, and the dealer resolved one of them but not all.

Since the Hill Start message also pops up when it flips to limp mode, I took a shot in the dark and replaced the stoplight switch. No success.

Checked the infamous trunk wiring, and found that there were some exposed wires where the sheathing had cracked. I wrapped each of the individual wires and then put a new sheath on. No success.

Have a theory about a sticky mechanism in PCV/AOS causing a buildup of pressure then a sudden release into the intake, causing the spike. New PCV/AOS assembly on the way.

That's about the extent that I'm willing to throw parts at it. Hesitant to return to dealer since they seemed to struggle with the diagnosis, but at this point I'm wondering about PCM/ECU and wonder if anybody who's not officially a Fiat shop having the right software to diagnose this thing.
 

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Discussion Starter · #9 ·
New PCV/AOS did not resolve the issue, although I note it's greatly improved. I probably had 200 miles of driving before it flipped into limp mode again.

Wit's end with this stupid thing.
 

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Discussion Starter · #10 · (Edited)
On a suggestion from the previous owner, I tried driving with the PCV hose disconnected, and capped off the barb near the throttle body where the hose was connected. That made things worse. It started going into limp mode/ESC off/Hill start assist unavail while I was on the highway. As usual, restarting the car returned behavior to normal, although in this case the car freaked out every few miles.

Codes I've been getting all along: P2172 P01046 P01048 P0104A P0104C
Codes I got with PCV disconnected (in addition to the codes above): P2173 P0105 P0106

As I type this, I realize, the cap I had over the PCV barb had blown off, which likely caused my issues above. Having said that, it makes me wonder: what would have caused all that pressure behind the throttle body, enough to blow off that cap? Because I would figure it should only have some suction, if anything, from airflow moving behind. Or is having positive pressure there normal?
 

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Okay, first and foremost, you should put the PCV back connected. Is there any other mods made to the car? P104(X) are the voltage range is off on the multiair actuators, so that seems to be a separate issue from the others. Check the wastegate actuator. It is adjustable, I wonder if it's out of spec. Wastegate is the first thing that people tend to mess with (or mod), so check that first. Try to put it back to as stock as it can. By the way, is there a piggyback ecu on this? What's the boost are you reading while it's running without CEL?
 

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Discussion Starter · #12 · (Edited)
It's all back in place now - connected as OEM intended. Symptoms remain periodically tripping limp mode with P2172 and the other four codes.

Next things I'm wondering.

1 - is there a way to tell if there's a piggyback or ECU upgrade? I've got TorquePro with a bluetooth OBDII reader. To a visual inspection, the ECU (or whatever the unit is on the battery tray) appears unmodified, and those connections appear OEM. Or is there another ECU/PCM unit elsewhere on the car that I should check? I can confirm the wastegate appears unmodified, comparing with some underhood shots via google images, but I recognize a visual check only goes so far. Boost gage indicates between 12-14 psi at WOT under load. Usually I'll see it hover in the 2-6 range under moderate acceleration.

2 - vacuum leak is a recurring suggestion. While I had the intake off I did an visual inspection of all the hoses I could find/trace using an inspection cam. Nothing else was obviously cracked/broken/disconnected, that I could see, from the top of the engine bay. I don't see any signs of oil leakage around the vacuum pump (which would make me question the integrity of the pump/seal). I do have a handheld vacuum pump/gage thingy from Mityvac, so I'm open to suggestions on where I should connect it and what conditions to test, what readings to expect.
 

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Your boost reading seems normal, so I'd say it's stock. The piggyback would be a separate unit, so you'd know if if's there. Reprogrammed ECU is hard to track, but going by the boost reading, it sounds like a stock one. The stock wastegate is adjustable, so you may want to check that to make sure that it's working as it should. There is not other ECU, but there is a BCM, that's where the inside fuse box is, but that's likely not related to any of this.

In the olden days when I was a wee little lad, we used to use propane to track down the vacuum leak. I'm hesitant to recommend that method...
 

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Discussion Starter · #14 ·
Haha. I've done that method using starting fluid, but never on anything built in the last decade or so. I did find a check for using the Mityvac to check the wastegate actuator, so I'll do that and report back. That should also confirm if it's stock and within correct range. Beyond that I'm grasping at straws. I see there's a purge valve which may be linked to some limp mode issues (if it's purging to the wrong place or at the wrong time) but that's more of a shot in the dark.
 

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Your boost actually seems low to me as my abarth boosts 18 pounds wot in sport mode 12-14 wot regular mode. And chills in the 6-10 range under moderate accel. The 2012-13's are notorious for having failure in the turbo/wastegate mine failed at 75k and blew shrapnel into the motor and destroyed it. Also check the bolts in your harmonic balancer and make sure they are all there. Mine came loose and caused the balancer to destroy the crank sensor. Eurocompulsion makes a boost solenoid (with new hoses and such) that is supposed to boost leak less than the factory one. Should be a couple videos on youtube for the common boostleak type issues, and there easy fixes. From what i have read seems like your map sensor may have **** the bed or has a broken wire. Fogging the motor is a great way to find vacuum leaks. Good luck.
 
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