Hunting unmetered air

--2016 w/DHM turbo kit

Hi All,

I started running into an issue under load in 3rd-4th gear at around 3500-4000rpm where the car falls flat on it's face, STFT goes through the roof (usually +30-50%) and boost cuts out. Basically all the signs of a boost leak. Then the car sometimes takes about a mile to recover to normal operation and STFT stays very high...I'm assuming due to some temporary limp failsafe in the ECU, or maybe the leak induced takes that long to seal back up.

Now, that second part has me thinking the leak could be pre-turbo inlet and unmetered air is getting into the charge system rather than boost pressure causing the leak. Just gut feeling.

I noticed on my CP-E intake the PCV breather hose connection didn't seem to seal well (see below). So I removed it and now am running a MAP intake which uses the factory crossover pipe and I still notice the hose doesn't make a very good seal. Myself and a shop have gone over all hoses from air filter to throttle body and insured all clamps are tight. My next step is to do a boost leak test using compressed air, but I wanted to ask here first if everyone else's breather hose is loose feeling at the intake side, if anyone has engineered a better way to seal that connection with a thicker o-ring, etc., or if I should look into ordering a new hose assembly.

I don't have any codes being thrown or pending.

I'm on the RAMAIR crossover pipe, using the factory breather line, and it seals well. I used some residual oil on my glove to coat the o-ring very lightly, and then pushed it on until I heard the *click*

Maybe you have too much heatwrap gathered in the area?
Have you tried removing some, and trying again?

How mine seals up




Sent from my SAMSUNG-SM-G935A using Tapatalk

Man, yours looks to lock in way better than mine. It looks like you have a '14-15 before they changed the design of the hose and added the pressure sensor, is that correct?


The pic I attached is with the CP-E intake, I don't have any heatwrap on the factory crossover pipe, so the tube should be in the same orientation as when it was built.

I do have a 15, good eye

Maybe you do actually need a new line, or perhaps a retro'd one from a 15?

Thanks for sharing those pics, that is going to be extremely helpful!

I think the newer version of the tube is more rigid and the connector could possibly be warped or damaged if not aligned 100% exact where it should be. An precise factory positioning was challenging with the CP-E intake and an aftermarket turbo.


Time to get crafty! ...or spend $60 for a new tube assembly.

If you can use the one from 2015, rockauto has them for $21.99!
https://www.rockauto.com/en/moreinfo.php?pk=4846422&cc=3308782&jsn=457

Post #12 & #20 may help you:

http://www.fiestastforum.com/forum/threads/16921-CP-E-Intake-Issues-on-2016-Fiesta-ST/page2

I ran into a similar issue and used a combination of a heat gun on the factory 2016 hose and a zip tie to hold the fitting in.

FYI, I still have the OEM turbo.

Interesting...

So I did some rearranging before I left the parking lot at work and I noticed the tube was *slightly* loose at the valve cover side fitting.

I further secured that end and messed around a bit at the intake side to try to better secure that end.

Initially, I think this might be the source of my leak. STFT only went up to +20%, but that was before I even merged onto the interstate (3rd-4th gear pull). I had no issue getting through 5500 rpm in 4th.

I'm going to reset learned trims and check the tube connections before each drive to see if it works itself loose again and how it relates to my boost issue/high fuel trims. But the changes I made today have made the car *so* much more responsive.

I think you are on a pretty wild guess ride to be worried about that breather hose to affect the stft by that much, something tells me is another thing
I have a 15 and I run something similar from what pelotonracer2 did to his car a lot time ago, been running it for a year on my car, haven't had any problems whatsoever. also have a damon catch can with VTA option, no problems whatsoever also.

Breathing in the good old hot engine bay air I see! you should buy some of those hood louvers and build a custom box to keep the hot engine bay air out...maybe even use a NACA duct...food for thought. I also have a Carbon fiber NACA duct in my garage flying around if you need one.........it also means introducing a hole in the hood.They work well I utilized one on my Typhoon with a custom box I made.

Don't get what you mean with your funny post but whatever floats your boat

What I'm getting at is with an open air filter like that ....the heat generated by the engine will be introduced into the intake system instead of Colder air from the exterior like you would get with a stock box with or without a velossatech snorkel or a st200 Air box with the air tube that goes to the exterior to pull in Colder ambient temperature air with or without a snorkel also. Just remember that the colder the air the denser it is and more can be crammed into the engine to generate more power.

This is not my setup, my setup is a st200 airbox.
Anyways, the point is not the intake, the point that i wanted to bring was eliminating the breather hose from the intake track to the valve cover, doesn't affect anything like the OP is bringing in question.

Also, i dont think this was posted on the forums, but @dizzy_tuning did make a intake tests with diferent intakes and the ramair crossover some time back
here are the findings:
https://www.facebook.com/Dizzytuning/posts/577877592567458
tldl:all intakes perform all close to each other, that means also the hot air intakes like the injen/aem/map

My concern isn't the breather hose itself as much as it is the possible leak at the hose to intake tube connection. If the leak is bad enough it can certainly add a volume of unmetered air into the system. Note the '16+ models have a pressure sensor added to this hose assembly now, as well. I'm not sure what impact that has on fuel calculations, but probably none.


So far, so good after my adjustments yesterday. I'm waiting on parts to come in for my leak tester so I can be more thorough.

If this car was the EU car i buy your explanation, but this car doesnt use the MAF for tuning. So in theory, it shouldn't matter if you disconnected it or not

^^^ What felopr said. The USDM uses MAP, manifold pressure for fuel calculations. Sucking air before the throttle body should not cause the problem you have.

I've read the numerous discussion threads on here about how our cars are MAP-based tuned and not MAF and I am not expert enough to argue against that consensus. But there has to be some credit given to the fact the issue was immediately resolved by adjusting the breather hose connection. My tuner also noted the MAF sensor does play a small role in fuel calculations and that issues can appear if there is an air leak on an aftermarket intake.


There is still plenty of time needed to verify this was actually a fix and of course I still am doing a boost leak test once I have the parts in hand. For the moment at least I am glad everything looks good, and back to being confused about this car's fueling strategy.

Your running a DHM system with a blow off valve?. Have you checked it to see if it is leaking boost-split diaphragm.

Alright, so I think I can finally say with confidence that I got this one figured out. The boost leak test looked fine but then the car started going nuts again a few weeks after my last post. I ordered a new o2 sensor and when I went to grab the wire the connectors just slipped apart. The shop that did some previous work didn't secure the connection, which caused intermittent signal loss from the sensor, which ultimately caused false readings to be reported to the PCM. One more reason why I usually opt to do my own work.

At least I have a backup o2 sensor now.