Fiesta st 2015 many problems

FIESTA ST200 USA MODEL 2015
Vehicle issue – multiple parts replaced, problem persists at high RPM



Hello everyone,

I’d like to summarize the issue and the work already done.



I have replaced the following parts, all brand new OEM Ford:

• Spark plugs
• Ignition coils
• Intake camshaft position sensor
• Vacuum lines
• Turbocharger

The initial problem was that after every refueling the engine would start very hard, needing 3–4 attempts. After replacing the parts above, the car now starts normally and no longer stalls while driving.



However, a new issue appeared: when engine speed exceeds ~5000 RPM, the check engine light comes on. During acceleration, the engine vibrates and produces a deep, rough sound. Because of this, I suspect a possible issue related to the camshaft phasers / VVT system.



On diagnostic scan, multiple fault codes appear, many of which seem unrelated to each other, and I doubt they represent real, independent failures.



At this point, I’m trying to determine whether:

• the ECU (PCM) could be faulty, or
• the issue is more likely related to the camshaft phasers / VVT control system (oil pressure, solenoids, timing, etc.).

And i need to add the car Has the intake air from cobb, if this matter.
And… my break pedal is very hard, why?
Any advice or similar experiences would be greatly appreciated.

Thank you!

What engine do you have?

ST200, JTJC engine code

Do you have an inspection camera?

Pull the plugs, inspect them too. Look for changes in thread or gap - look for hammering - it means you may have the issue of too advanced VVT or the valve train itself is not timed correctly (in advance or TDC) so the plugs may get hit too - meaning oil pressure issues and the piston to head distance is too close due to the timing is not right.

Misfires signal a combustion chamber not at the right mixture or not enough to combust - poor vacuum.

Can also set an over-speed condition where the cams centrifugally are advancing more than the oil pressure would allow per sensor readings at the camshaft position sensors.

Also check the grounds - errant spark noise can cause errors in reading due to the noise induced by poor spark plug gapping.