Hi all. New here and having issues with my 1.8 petrol zetec. It seems flat until I hit 4500rpm and then it takes off! I've cleaned the throttle body but this hasn't helped. Any ideas? 

cheers

The symptoms you describe are common when the swirl flaps are stuck. When the swirl flaps are stuck in the position for high RPM's the engine feels gutless and underpowered at low RPM's 

The Duratec HE engines have swirl flaps inside the intake manifold. These swirl flaps modify the air flow within the intake manifold and have 2 positions. 1 position for low RPM's and 1 position for high RPM's. The swirl flaps are vacuum operated and controlled by the PCM using 2 actuators.

Malfunction of the swirl flaps is a common problem on the Duratec HE engines. This can either be caused by a mechanical fault like the flaps being stuck, broken or even completely gone (sucked into the engine) or by an electrical fault like defective actuators.

 

Thank you very much. I will have the inlet manifold off tomorrow and see if there's anything obvious. Will keep you updated 

On 12/30/2021 at 4:35 PM, Red_mk2focus said:

Thank you very much. I will have the inlet manifold off tomorrow and see if there's anything obvious. Will keep you updated 

The swirl flaps were modified for the version of the Duratec engine fitted in the MK2 Focus, so they're much less prone to failure.  The most likely culprit are the solenoids that control the 2 flaps, although it's unlikely that both solenoids have failed.  Assuming only 1 solenoid is dead, if you swap the little vacuum hoses round so they fit the 'other' solenoid respectively) and take it for a test drive, if the solenoid for the 'high RPM' flaps is faulty then although it might drive worse at low RPMs it'll drive better at high RPMs due to the flaps actuating correctly.

 

I replaced this part on my wife's MK2.5 1.8 with a cheap part off Amazon about 18 months ago and it's still going strong.