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Thread: Boost Leak Tester recommendations and hesitation/stutter question

  1. #1
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    Boost Leak Tester recommendations and hesitation/stutter question

    Just out of curiosity, is there a particular boost leak tester that you guys recommend for our cars (size, brand, etc.)?

    Figured it wouldn't be a bad idea to invest in one to do an occasional check. And at what PSI should I test at?

    My car seems to be running fine but I do once in a while get a hesitation or stutter at or above 5,000 RPMs when accelerating. It's almost like hitting a limiter (no backfires when this happens). When it did occur, it is usually when I am accelerating at greater than 50% throttle but less than 100% throttle. I initially figured maybe I was confusing the ECM and it wasn't sure if it wanted to continue boosting or back off boosting. But most recently it happened to me at full throttle. Most instances it is in 2nd gear (manual mode). Letting off the throttle and reapplying throttle or shifting gears it will go away. This has occurred both with my stock intercooler as well as with my most recent installation of my ATM FMIC.

    Is this one of those little known characteristics/glitches/features of the car or is it something I need to look into?

    If it is something that can be remedied, would this be a result of a boost leak or more likely something to do with the coil packs and/or spark plugs?

    I've been thinking about upgrading the coil packs and spark plugs anyways. Whether I do it sooner than later I guess the suggestions I get determine.

    My 2015 Abarth Auto I bought new August 2015 and it has just over 13,000 miles on it. No CELs. With exception to these once in a while instances (which I believe it has done since I bought the car), the car runs smooth. Only mods I have are the Madness Maxflow Intake (soon to be replaced with the ATM fenderwell intake), a GFB DV+, Sila Concepts thermal blanket, and the ATM FMIC. Everything else is stock, no tunes.

    Thanks!
    2015 Fiat 500 Abarth (Red Rosso, automatic)
    ATM FMIC
    GFB DV+ Diverter Valve
    Madness Maxflow Intake System
    Sila Concepts Thermal Blanket

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    Bueller? Bueller? Anyone? Anyone?

    Thinking more about it, I wonder if the hesitation “hitting the limiter” like experience is from the car either seeing or thinking there is throttle lift off when it is under full boost. As such, I would think if it is just trying to cut fuel and dump some boost to get it at the level it is expecting or trying to predict at where the throttle position is going. Maybe it’s just really sensitive and reactive to throttle position as a safety measure? As such, maybe it gets a little confused or finicky? To the point where maybe it is more sensitive to throttle input than I, myself, am aware of?

    Just thinking out loud here, so I apologize for the rambling.
    2015 Fiat 500 Abarth (Red Rosso, automatic)
    ATM FMIC
    GFB DV+ Diverter Valve
    Madness Maxflow Intake System
    Sila Concepts Thermal Blanket

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    I have heard of a malfunctioning PCV valve causing a stutter at higher rpms, particularly under heavy throttle.
    2013 Fiat 500T Rosso
    RRM rear sway bar, Koni front struts, El Gato front chassis braces, 500Madness GoPedal, NeuF muffler delete, EC V4.1 intake, Gofastbits DV+, RRM lightweight crankshaft pulley

    2016 Fiat 500X Pop Arancio
    500Madness GoPedal, custom Abarth style exhaust (resonator/muffler delete.), Gofastbits DV+, LED interior lights.

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    Quote Originally Posted by carfreak09 View Post
    I have heard of a malfunctioning PCV valve causing a stutter at higher rpms, particularly under heavy throttle.
    Thanks, that's good to know and I will keep that in mind. Although I find it difficult to believe that the PCV can be malfunctioning with only 13,000 miles on the car, anything is possible. Should be a fairly easy thing to check and relatively cheap to replace if I need to.
    2015 Fiat 500 Abarth (Red Rosso, automatic)
    ATM FMIC
    GFB DV+ Diverter Valve
    Madness Maxflow Intake System
    Sila Concepts Thermal Blanket

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    Quote Originally Posted by VirtualMirage View Post
    Thanks, that's good to know and I will keep that in mind. Although I find it difficult to believe that the PCV can be malfunctioning with only 13,000 miles on the car, anything is possible. Should be a fairly easy thing to check and relatively cheap to replace if I need to.
    A minor sampling but significant nonetheless is the fact that 2 people in my local fiat owners club has had the PCV valve fail. One failed with less then 20k, the other with around 50k. The second one was the one who had a maddening stutter that only occurred at rpms over 5k. He took it to the best Fiat tech in central Florida who finally was able to diagnose it as the PCV valve. After it was replaced, the stutter went away. So it's definitely worth a look. The only other possibility would be the coil pack.
    2013 Fiat 500T Rosso
    RRM rear sway bar, Koni front struts, El Gato front chassis braces, 500Madness GoPedal, NeuF muffler delete, EC V4.1 intake, Gofastbits DV+, RRM lightweight crankshaft pulley

    2016 Fiat 500X Pop Arancio
    500Madness GoPedal, custom Abarth style exhaust (resonator/muffler delete.), Gofastbits DV+, LED interior lights.

  6. #6
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    When my car acted like that, it had over 50,000 miles on it. All I did was spark plugs from Amazon (I gapped them) and a set of oem coils from RockAuto. At 13k miles its unlikely to be spark plugs or coils, but since you are going to upgrade the coils anyway I say do them first since you have net benefits over stock coils. Then if you continue to have issues, take it in and tell them to verify the PCV stuff.

    Ciao ciao
    PE#389

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    Thanks all for the advice. On the one hand I am glad that its occurrence is rare (it would really sour the enjoyment I get out of the car if it happened all the time), on the other hand it bugs me because it makes it harder to repeat and troubleshoot. A bit of a double edge sword. All I do know is the observations I noticed when it does occur, albeit random occurrences that have happened through most of my 1+ year ownership (bought the car new less than 200 miles on it).

    As for taking it in, I'd prefer to do as much as possible myself. The closet studio is 2 hours away with weeks of backlog which would require me to take a full day off of work just to go up for troubleshooting. With as cheap as PCV valves are, I don't mind spending that out of my pocket to replace since I would be losing even more in gas and my time going to the dealer. Inspecting a PCV doesn't seem to be too difficult and doesn't seem to require any special machinery.
    Last edited by VirtualMirage; 10-12-2017 at 05:29 PM.
    2015 Fiat 500 Abarth (Red Rosso, automatic)
    ATM FMIC
    GFB DV+ Diverter Valve
    Madness Maxflow Intake System
    Sila Concepts Thermal Blanket

  8. #8
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    Decided to record the sound of what I assume is my PCV valve in action. The noise it makes in this video sounds kind of like a "flutter" or "popping" noise. The noise isn't new for me, I first noticed it within the first few months of ownership around this time last year. At the time, I took it as being normal, figuring that having it vent to atmosphere with a filter on it instead of piping back into the intake made the noise more pronounced. But now, with the attention of some brought to me that my occasions of hesitation at high RPMs might be PCV related, I figured I would record the noise and post it for the "experts" to chime in. Since there is at least a noise and it is more of a "flutter" like a valve opening and closing many times, I would like to think that is how it is supposed to sound, but I could be wrong. In the video, it gets louder as I get closer to the PCV filter and quieter as I move away. In person, its sound is more distinctive and doesn't get lost in the engine noise like it may in the video.

    Last edited by VirtualMirage; 10-15-2017 at 09:00 PM.
    2015 Fiat 500 Abarth (Red Rosso, automatic)
    ATM FMIC
    GFB DV+ Diverter Valve
    Madness Maxflow Intake System
    Sila Concepts Thermal Blanket

  9. #9
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    So another update:

    I think I am going to order some new coil packs and spark plugs today (providing that is where the feedback takes me). I might even pick up a new PCV just in case. The hesitation/stutter issue happened again this morning. Like I mentioned before, it's like hitting a power limiter. You are telling it you want it to go, the car feels like it wants to go, but something is artificially holding it back.

    This morning it was about 48 degrees, the car was fully warmed up (driven for about 30-40 minutes), I just filled up the tank this morning with Shell V Power 93, Sport mode on, ESC fully off. From a rolling start I began a hard acceleration midway through 1st gear, shifted to 2nd a little above 5,000 RPMs with no issues, but when I got to around 5,000 RPMs in 2nd the car hesitated/stuttered again. I shifted to 3rd with throttle still at 100% and in the mid-high RPM range it stuttered again right before I was going to shift to 4th and letting off the throttle. What I didn't mention earlier was the sound the exhaust makes. I guess some may refer to it as the car letting one rip, just a long fart noise ("brrrrttt") until you let off the gas (no pun intended). To me it sounds kind of like that with a little hint of A-10 vulcan cannon or jake brake character to the sound. No CEL, idles and cruises smoothly. Whenever I hear that noise and feel that "virtual wall" I immediately either let off the gas or change gears, I don't let it try to fight its way through. So the event only occurs for a fraction of a second.

    I am thinking on getting the 4C coil packs unless convinced otherwise. As for spark plugs, I'll probably go with the NGKs. While I don't have a tune (yet), should I gap them to stock spec or tune spec since I have an intake, FMIC, DV+, and thermal blanket?

    I'll probably get some kind of data logger as well. I read that some people that experienced a similar issue noticed their throttle was closing. Of course, the throttle was closing due to other factors and is just the car's way to protect itself if it detects knock, overboost, etc. Of course, these could be due to one of many things: boost leaks, faulty waste gate, poor ignition (coil pack or spark plugs), bad fuel, failing PCV, clogged PCV hoses, etc. IIRC correctly, I thought I read somewhere that venting the PCV to atmosphere could even be a possible contributor (but not quite sure how so). So then, if that is the case, I'd have to figure out what is the culprit.

    I still haven't received or seen any suggestions on what kind of boost leak tester to get (size, brand, etc.).
    2015 Fiat 500 Abarth (Red Rosso, automatic)
    ATM FMIC
    GFB DV+ Diverter Valve
    Madness Maxflow Intake System
    Sila Concepts Thermal Blanket

  10. #10
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    Looking around, I believe I confirmed that the inlet on the turbo is 2". Going by that, I went ahead and ordered a boost leak tester from here:

    http://turboboostleaktesters.com/2-inch/

    I ordered it with the 30 PSI test gauge, the tire valve, and an extra clamp. The price seemed reasonable and it comes with everything needed to do the test (minus the compressor, which I have). I'll give an update on how well it works when I test it out.
    2015 Fiat 500 Abarth (Red Rosso, automatic)
    ATM FMIC
    GFB DV+ Diverter Valve
    Madness Maxflow Intake System
    Sila Concepts Thermal Blanket

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