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2013 Chevrolet Sonic - Hissing noise, high Fuel Trims, high fuel consumption


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nightmaim
User

Jan 4, 2018, 5:33 AM

Post #1 of 13 (715 views)
  post locked   2013 Chevrolet Sonic - Hissing noise, high Fuel Trims, high fuel consumption  

Hi all!

I have a 2013 Chevrolet Sonic with an Ecotec 1.6 engine. The car is making a hissing noise coming from the right side of the engine. I'll be very detailed in this post with my findings so far because I'm trying to solve this issue from an entire month ago.Unsure


The symptoms are:

-Increased fuel consumption (17 mpg) mixed city/road

-Total fuel trims are high when idling, around 40% (STFT plus LTFT) accordingly to the scanner only going down to an average of zero when RPMs are high, at least more than 2k.

-Sometimes the car hesitates to launch, but once is running, power output seems to be normal. In rare occurrences, the car struggles to maintain idle, but when it does, I'm even afraid of taking off because will run like s**t for a few moments.

-When cranked, the engine immediately boosts to around 2.5k RPM, it feels like I was accelerating while cranking.

-From time to time, check engine light comes on throwing the code P0366, which points to the camshaft position sensor, exaust side. After some time, the light turns off, and nothing changes between this period.


What was done so far:

Since the P0366 code is the only error code I have, I changed both intake and exaust camshaft position sensors, no success.

Both intake and exaust camshaft actuators (part of the VVL system) were removed, inspected and cleaned with carb cleaner. They was already clean.

ECU was reset by leaving the battery off overnight.

I've already replaced the infamous PCV valve *again* but that was not the problem this time. (another story)

Then since the nearest place I could pinpoint the hissing sound was the intake manifold tuning valve, I disassembled it, but both the o-rings and the diafragm were in good shape, I also did the smoke test to ensure the valve is not leaking.

Next, I disconnected the brake vacuum lines from the intake manifold and tapped with a duct tape, the hissing noise persisted.Mad Also, the power brakes electrical vacuum pump was disconnected from the power source.

I discarded the throttle body gasket because it is located on the opposite side of the intake manifold, so the noise was clearly not coming from there.

Another guess was the EVAP valve, but that had passed on the smoke test and is also located away from the source of the hissing noise, it's next to the throttle body.

MAF is crystal clear. I also cleaned the throttle body with TBI cleaner, that one was dirty.

I'm afraid that I can have a blown intake manifold gasket, it is very difficult to test the insulation because of the tight space, also, it doesn't make sense to me, a car with 70k miles to have a blown gasket like this. I don't know what else to test, is there any other thing that can make this same type of noise and have relationship with the symptoms above? Maybe I'm too concentrated in trying to find a vacuum leak when in fact could be something completely different.

Also, I don't understand what (or even IF) the P0366 code has to do with all this, including the hissing noise, of if is a completely different issue.

And finally, a last clue: The PCV valve had failed at around 50k, sending oil vapours to the engine through the intake manifold. That was fixed pretty quick, but it is possible that the oil could have damaged some gasket?

Please help Unsure

Marco


Discretesignals
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Discretesignals profile image

Jan 4, 2018, 6:38 AM

Post #2 of 13 (693 views)
  post locked   Re: 2013 Chevrolet Sonic - Hissing noise, high Fuel Trims, high fuel consumption  

You sure it is 1.6L? That year either had 1.4L turbo or 1.8L

The way your fuel trims are acting, I'd would suspect a vacuum leak. If you have a smoke machine, smoke the intake when the engine is cold. Be sure to cap off the intake ducting.





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nightmaim
User

Jan 4, 2018, 7:47 AM

Post #3 of 13 (686 views)
  post locked   Re: 2013 Chevrolet Sonic - Hissing noise, high Fuel Trims, high fuel consumption  

Yes, the 1.6L version is called LFJ, very similar to the 1.8L version. These units were not destinated for the US/Canada market, that's why it's hard to find.

I do not have a smoke machine, the little smoke I could blow was from a cigarette hehe, even though I do not smoke.

At that time, there was no signs of leaks from the top of the intake manifold, I cannot say the same for the bottom part because I cannot see the smoke there.

One idea was to use a garden hose, with little amount but pressurized water spraying from the bottom to the top while paying attention to the hissing noise, I dunno, I'm open to ideas...

I plotted a chart of the fuel trims based on the scanner output, maybe that helps: https://s18.postimg.org/5ih4ho8wp/Chart.png

Thanks!!


Tom Greenleaf
Ultimate Carjunky / Moderator
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Jan 4, 2018, 9:04 AM

Post #4 of 13 (679 views)
  post locked   Re: 2013 Chevrolet Sonic - Hissing noise, high Fuel Trims, high fuel consumption  

This totally smack of a vacuum leak - you can hear it! Smoke machine or other ways. Cigarette probably not as useful or productive for smoke for that.
Other ways: Look at brands of brake cleaner spray. The brand name "Bra-Kleen" is almost a fire extinguisher not flammable and says so others are so read if used. That leak enough to make a noise it would stall.


Other but totally risky is a propane torch not lit right at the spot would change RPMs. Play smart be ready if it flashes flames. Mists of plain water. If the noise is it and almost certainly is move on to really soapy bubbly water in spray bottle perhaps if bubbles enough on target spot might see the spot shrink bubbles so you are sure where and can take action of what to do as it remains unknown if simple or a crack in something?


T



nightmaim
User

Jan 4, 2018, 9:29 AM

Post #5 of 13 (669 views)
  post locked   Re: 2013 Chevrolet Sonic - Hissing noise, high Fuel Trims, high fuel consumption  

Alright, thanks! I'll do the water trick all around the intake and post the results here.

Marco


Double J
Veteran / Moderator
Double J profile image

Jan 4, 2018, 6:02 PM

Post #6 of 13 (655 views)
  post locked   Re: 2013 Chevrolet Sonic - Hissing noise, high Fuel Trims, high fuel consumption  

Check the Air Intake Duct that goes from the Air filter housing to the Throttle Body

The ducts on the 1.8L were all cracking. Replaced a few already- Affects the 2012-thru 2014 1.8L
(I know yours is a 1.6- you said its similar, so I figured I'd mention it)

It usually sets a P0171 lean code and/or a P0101 Mass Air Flow Sensor code
They (GM) recently came out with a Special Policy on these (1.8L's) to extend the warranty on this part only and replace those that are cracked

Its easy to overlook so take yours off and inspect it, can't miss it once its off.
I usually see cracks in 2 places.

Starting to see it appear on other models now also,like Impalas


(This post was edited by Double J on Jan 4, 2018, 6:08 PM)


nightmaim
User

Jan 5, 2018, 2:51 AM

Post #7 of 13 (625 views)
  post locked   Re: 2013 Chevrolet Sonic - Hissing noise, high Fuel Trims, high fuel consumption  

Good point JJ, I'll check that for sure.

Thanks!


nightmaim
User

Jan 31, 2018, 4:28 AM

Post #8 of 13 (500 views)
  post locked   Re: 2013 Chevrolet Sonic - Hissing noise, high Fuel Trims, high fuel consumption  

Well, I managed to find the leak, but as Murphy's law states, it is in the worst place ever, in a hose connection of the intake manifold, located in the gap between the cylinder head and the intake manifold, next to the 2nd cylinder. I had to buy a smoke machine to find that and look from below the car, because it is absolutely impossible to see from the hood even with a spy camera!

I hope it helps someone one day, here it goes the pictures:

View from below, needs to remove the oil pan guard:
https://drive.google.com/...miM/view?usp=sharing

Point of view of the video above and damaged part:
https://drive.google.com/...wj4Bol3DnIqFVdxC4WII

By the way...does anyone knows the name of this hose & connection?

Thanks!!


(This post was edited by nightmaim on Jan 31, 2018, 4:42 AM)


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jan 31, 2018, 6:18 AM

Post #9 of 13 (483 views)
  post locked   Re: 2013 Chevrolet Sonic - Hissing noise, high Fuel Trims, high fuel consumption  

It looks like you just have to remove the intake manifold which is not that big of a deal. Just bring that picture to the dealer and they will easily identify it. They are likely the only ones that will be selling it anyway..



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



RobertHPAllen
New User

Feb 1, 2018, 3:16 PM

Post #10 of 13 (430 views)
  post locked   Re: 2013 Chevrolet Sonic - Hissing noise, high Fuel Trims, high fuel consumption  

Blown Headgasket


General Motors has a real problem with headgasket sealing and it causing a hissing leak close to the exhaust valve at the center cylinder.

Right in the midle of the block.


nightmaim
User

Feb 2, 2018, 4:53 AM

Post #11 of 13 (410 views)
  post locked   Re: 2013 Chevrolet Sonic - Hissing noise, high Fuel Trims, high fuel consumption  


In Reply To
Blown Headgasket


General Motors has a real problem with headgasket sealing and it causing a hissing leak close to the exhaust valve at the center cylinder.

Right in the midle of the block.


That's not the case. The leak is in a hose connection located at the front face of the intake manifold. Also, this hose connects to the manifold itself, check my last post.

I'm curious about the purpose and name of this hose...


nightmaim
User

Feb 5, 2018, 10:01 AM

Post #12 of 13 (376 views)
  post locked   Re: 2013 Chevrolet Sonic - Hissing noise, high Fuel Trims, high fuel consumption  

OK, that worked. I managed to remove the valve from the intake manifold without removing the entire part. It's a "L" shaped air check valve, and for some reason it looked extremely corroded and even had a hole on it.

https://preview.ibb.co/...1b7_37e193f90002.jpg

I couldn't find a replacement part, in fact I had little time to search for it, then I decided to fix it myself using epoxi cement. Luckly the internals were working properly, only the external was bad.

The repair was a success. After 100 Km of testing, I could ensure that the fuel trims lowered to +3.7% in average, the hissing noise is gone, fuel consumption decreased by 27%, even the shifting errors, specially in 3rd gear disappeared. Car is running like new.

Thank you all for the help.


(This post was edited by nightmaim on Feb 5, 2018, 10:02 AM)


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 5, 2018, 9:14 PM

Post #13 of 13 (354 views)
  post locked   Re: 2013 Chevrolet Sonic - Hissing noise, high Fuel Trims, high fuel consumption  

You're welcome. I'll close this now as solved.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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