Low Boost

[racingmason23]

Ok so lately I have noticed a decrease in power and fuel mileage. Using my tablet to view pids I am only building 10 psi of boost on my lms 4 plus. I get the same on the stock tune. Last week I was pulling 12.3 psi max on the 4 plus. I should be significantly higher psi then that. I have checked the hoses and didn't see anything ovbious. I have a boost leak tester but it is for a single turbo setup.

Im not sure if its a leak or if a bov is failing.  If I build 3 psi of boost and roll off the throttle slowly they stay open for a few seconds.

Also plus are sp 528s with 2000 miles on them.

 

[BigPelo]

Sound like a Boost leak to me. Have you check the hot pipes?

 

[BiGMaC]

Definitely sounds like a boost leak.  Check the plastic hotpipes and silicon connections for cracks.  tighten the clamps on the silicon connections...

If the tubes are cracked you can have a dealer replace them.... or do what many of us have done, go to a metallic hot pipe so the leak won't happen again.  Ecoboost Power Parts has them in several finishes and configurations.
http://shop.ecoboostpowerparts.com/Ford-Flex-SHO-Lincoln-MKT-MKS-Hot-Pipes-EB-HotPipes.htm

 

[bpd1151]

As others have suggested, check the plastic piping on the pressurized side of each turbo.

There aren't any silicone connections in the factory setup.

The hose that has most often failed is the approx. 11" rubber hose that transitions from the IC to the Front Turbo.

I'd check that one 1st, & be thorough.

Sent from my DROID RAZR HD using Tapatalk

 

[racingmason23]

Will do. What is factory boost level? Anyone know what the lms 4 plus should hit? They didn't give me a number.

 

[ecoboostsho]

Where are you measuring your boost?  At the top of 1st?  I typically only hit 12-13 PSI when I floor it in first.  In higher gears a max of 10-11 PSI seems normal for my car with 4+. I've also noticed that in colder weather the car seems to dial back the boost...

You could pull the battery cable for 30 minutes and see if your boost comes back...this car learns and pulling the cable will reset it again.  If it does then you don't have a boost leak.  If it doesn't then check all of your clamps (wouldn't hurt anyway)...

 

[FoMoCoSHO]

Is it cold where you are?

Stock tune tapers boost down as temps decrease to compensate for denser air.