Hi i have a 2009 mk2 focus zetec s 1.6 vct.I have a problem with intermitant loss of power.One min it is performing well the next it is surging and driving like the handbrake is on.I have changed coil pack plugs leads cleaned maf sensor throttle body and the cat.I have also had the instrument cluster re soldered.Ihave no codes showing or stored in the ecu.This is doing my head in if anyone can help would be much appriciated.

When you say you have no codes, what have you used to read the codes?

When it goes into poor performance mode, do you get any warning lights?

The next time it does it, pull over and see if the brake lights are stuck on.

Hi thanks for reply.I have had it rigged up to two expensive snap on diagnostics readers both showing no codes and i do not get any warning lights at all when it starts to perform badly.

The next time it does it, pull over, whilst engine is running, and open the fuel cap (if it's capless push the filler/funnel tube in to open), if you hear a large hiss then the fuel tank breather is blocked and you will need to investigate and clear the blockage.

Other than that, I don't know other than you have sticky valves that get worse the longer you drive/hotter it gets.

Change the oil, fill up with super unleaded, plus a full bottle of redex, drive vehicle on motorway and after about 10 minutes run the car in 3rd gear over 60 MPH for about 10 minutes or as long as the engine speed is above 4,500 RPM to give it a blow out

Are you sure you fitted the correct plugs?

Any performance issue that doesn't throw the money light or show codes is likely to be fuel related, can you change the fuel filter as a test. Do you know someone with a Fuel pressure test gauge?

The above mentioned test for excessive tank vacuum is highly likely to throw an evap code and pop the money light on so whilst i wont dismiss the test I'd personally not even suspect that as an issue. 

Hi steve thanks for your reply i will investigate if the fuel filter is blocked hoping it is situated under the car and not inside the fuel tank as that will be a complete nightmare of a job.

7 hours ago, Great1 said:

Hi steve thanks for your reply i will investigate if the fuel filter is blocked hoping it is situated under the car and not inside the fuel tank as that will be a complete nightmare of a job.

Unfortunately the Fuel filter is in the tank on the Duratec/Sigma 1.6.

Hi, I had this issue and it turned out to be the wiring between the coil pack and ecu

20 hours ago, steplce74 said:

Hi, I had this issue and it turned out to be the wiring between the coil pack and ecu

Thats likely to throw the money light on and give some codes