Hissing noise under acceleration

[GearJamr]

So, I recently had ELH headers and catless up-pipe installed and I did the vacuum T mod.  Since then I am hearing a hissing sound when accelerating.  When at steady throttle, the hiss goes away.  The sound MAY have been present before the header/up install but I did not notice it before.  

With my tuner on Friday, he noticed the ECU is adding fuel at idle, and at cold start I can smell fuel fumes now.  Vacuum is very strong now.  He suspects a pre-turbo intake leak.  Would it be best to get a smoke test done rather than just swap the intake?

Anything else I could be missing?

TIA

[Max Capacity]

Yes, smoke test or boost leak test using air and listen for leaks. 

I use a pint size paint can to plug the hose off the air filter box, pull small hose from BOV, give that hose a short blast of air from my compressor, put thumb over hose.

[Max Capacity]

You may have a tare in the turbo inlet hose at the turbo. That's one reason I use bolts to hold the turbo on the up pipe. The studs make it hard to line the turbo and can put stress on that old inlet tube.

 

[GearJamr]

So, in all likelihood, the tech who installed the up-pipe damaged the inlet tube?  The large L shaped intake runner from the air box looks okay, but it's hard to see it all.

[Max Capacity]

Yes, it's hard to see all of it. Mine tore an inch or so in front of the turbo. There is a flexible area there.

[KZJonny]

Fwiw, I picked up the autoline pro tester, and it has been handy.

https://www.amazon.ca/AutoLine-Pro-Automotive-Detector-Diagnostic/dp/B07JVT1NG2/ref=asc_df_B07JVT1NG2/?tag=googlemobshop-20&linkCode=df0&hvadid=337141350629&hvpos=&hvnetw=g&hvrand=895112415206176707&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9000774&hvtargid=pla-571637951948&psc=1

The other methods all around work, but rather than spraying soapy water all over the engine bay, I liked that this would give me a clue where to look for leaks…. I’ve loaned it out to another GT owner who was tracking down some issues as well. Worked a treat finding tiny leaks at his TGV actuators…

It’s more than a paint can lid for cost, to be sure, but was about the same price as having a smoke test performed at a shop, so I called it a wash, and now have one for keepsies.

[Tehnation]

If the turbo inlet were torn it would be noticeably performance wise I thought. Does the car drive any worse, any hesitation, or rough idling? 

[Tehnation]

On 9/6/2022 at 6:18 PM, KZJonny said:

Fwiw, I picked up the autoline pro tester, and it has been handy.

https://www.amazon.ca/AutoLine-Pro-Automotive-Detector-Diagnostic/dp/B07JVT1NG2/ref=asc_df_B07JVT1NG2/?tag=googlemobshop-20&linkCode=df0&hvadid=337141350629&hvpos=&hvnetw=g&hvrand=895112415206176707&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9000774&hvtargid=pla-571637951948&psc=1

The other methods all around work, but rather than spraying soapy water all over the engine bay, I liked that this would give me a clue where to look for leaks…. I’ve loaned it out to another GT owner who was tracking down some issues as well. Worked a treat finding tiny leaks at his TGV actuators…

It’s more than a paint can lid for cost, to be sure, but was about the same price as having a smoke test performed at a shop, so I called it a wash, and now have one for keepsies.

I did the same thing, why keep paying 100+ dollars for smoke tests when you can just buy a kit, and do it yourself whenever. 

I got this guy of Amazon

https://www.amazon.com/gp/product/B0746SL9D6/

[GearJamr]

7 hours ago, Tehnation said:

If the turbo inlet were torn it would be noticeably performance wise I thought. Does the car drive any worse, any hesitation, or rough idling? 

Idle is good, except for the ecu adding excess fuel (according to the tuner's software).  During "normal" driving there is slight hesitation/stumble.  From low rpm and going WOT there is plenty of hesitation/stumble, particularly in 2nd gear.  In 3rd it is noticable but reduced, and 4th and 5th it is minor, just hiccups.  Doing a pull from a standing stop reveals none.

[Tehnation]

have you checked all your vacuum lines? Especially the notorious blue tee behind the intake manifold and between that and the intercooler? Might just be a disconnected hose as well. If its that loud and noticeable you should be able to spot the problem by eye imo. Do you have access to an air compressor? The cheapest and fastest way to find a leak if you have an air compressor imo is to get a 3" pvc pipe rubber end cap, something like this https://www.homedepot.com/p/Fernco-3-in-PVC-DWV-Flexible-Cap-PQC-103/100372304, and cap off the air intake, then you pull a vacuum line from the ebcs or fpr or whatever, and just push like 25 psi through the system and listen for something, increasing the psi until you find it. For hard to find or small leaks, bust out the soapy water and spray bottle! 

Now would also be the right time to learn the entire vacuum system! Once you memorize all the lines and know exactly how the vacuum lines are routed, finding leaks becomes a lot easier, versus looking at something and just seeing a mess of tubes, wires etc. Basically all the vacuum lines start at 1 of 2 places the intake manifold and the turbo inlet hose. Turbo inlet hose has like 3 or 4 lines( ebcs, fuel vapor/purge thingy, recirculating valve, and I think one more line to something pcv system maybe?), and the manifold has like another 3 or 4(pcv, brake booster, the T  and the one on the side by cylinder 4 for the fpr).... can't remember exactly but thats my best guestimate. 

[GearJamr]

Not that it isn't a possibility but tuner said the vacuum is very strong.  I'm waiting on a proper brass T to get delivered and then I will replace the blue one.  When I checked it out previously all was good, and that was shortly before this all started.  Soapy water might be the easiest thing to try.  If that doesn't show something obvious, will have to go with smoke test.

[Tehnation]

Vacuum leak would probably throw a code as well..... so before mods it sounded one way then after it sounded another way? The sound didn't change while the new mods were installed? So maybe the headers and uppipe are just louder? But you have performance issues. 

What does an exhaust leak do? That will throw a code as well I think... maybe not. Someone else might now. 

Does it make the sound when your in neutral an give it gas or only under boost? 

Whats your intake? Stock? Did you check to see if the box is closed properly? 

 

[GearJamr]

No codes.  New O2 sensors in downpipe and headers.  New EGT sensor in up-pipe.  

I did not notice the hiss prior to the header/up install.  Do not recall it being present after tbe install.  I'd put it at 95% certainty it was not there before.

Have not tried revving while in neutral.  I notice it primarily at lower rpms, like 2-3k range.  I do not have a keen enough ear to tell if it is still there after the exhaust gets loud.

Stock intake.  I replaced the air filter prior to the header/up install and double-checked the box after the hissing started.  I thought maybe I had forgotten to tighten the worm clamp on the intake but it was also snug.  

I no doubt had a downstream exhaust leak prior to the tbe replacement and never got a code but they were after the O2 sensor so it likely thought everything was fine.