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Turbo life at half Throttle. (Please Help!)

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Hi everyone.

I'm one more ETC light and throttle cutting limp mode away from burning my car to the ground.

A year-ish ago some of you may remember me searching for help to get my BA XR6T engine running in my blown up BF XR6 on its NA PCM.

Fast forward to today and I'm loving the car, except for when I try to overtake or have a little fun.

In any gear (Auto) you can not rev past 50% throttle travel.

In Park it revs to the floor no issues.

It was suggested that my ABS sensors may be dirty, they were indeed dirty, but weren't the problem.

I've since tried a different TPS, different Throttle Body and checked the entirety of the engine for vacuum leaks or the such, no dice.

I'm throwing one code P0420, which stumps me because as far as I know that's a BF code, and I've got a BA tune.

Has anyone else had this issue? I've found similar ones but none trigger like mine do.

Could no boost refernce in the PCM cause this?

My tuner left the factory boost control in the tune, and due to the problem im having I've not yet been able to road tune my GFB Boost Contoller.

My boost gauge has never read higher than 4.5 PSI and cuts at any boost level.

I did notice my AFR gauge reads around 10.00 before it cuts. Rich? 


I appologise for the barrage of questions.

Thanks legends. 

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code P0420

do you have single 02 sensor like the BA spec or twin 02 sensors like the Bf spec?

if your using a BF ecm I would make sure your secondary 02 sensor is turned of correctly



AFR in the 10 is indeed verry rich, if you want to play along with 02 sensors issue then you can look further into the enrichment the ford ecm will do when it thinks the cat converter is to hot.. obviously works this out based on the 2 02 sensors (up and downstream of the cat).


  • Fuel enrichment on catalytic converter over temperature
  • Fuel enrichment on exhaust over temperature
  • Fuel enrichment on turbo over temperature

Otherwise - are your injectors leaking?


A boost level of 4.5psi is not enough to induce torque reduction on factory b series boost map. 

are you sure its cutting and not just misfiring from over-fueling, due to your potential bad 02 sensors programming or hardware?

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Hi mate, thanks for the reply.


Just had the PCM retuned, still having the issue but I'm throwing a different code now.


I have an idea, I was checking my PCV valve vacuum line routing today and noticed my line doesn't have a Check Valve in it.

Could this be the source of my issue? Boost pressure in the rocker cover?



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Throw the gfb boost controller in the bin and put the stock controller back. All aftermarket systems go backwards over stock. 

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