Mk2 Mondeo - Rough Idle - Juddery @ 2250-2750 Rpm

[SNAKEBITE]

Hi,

I was wondering if anyone could help me out. The problem is with my Mk2 Mondeo which is a P plate and has 133,000 miles on the clock.

Background

• It had its MOT in February where the catalytic converter, lamda (?) sensor (screws into downpipe), leads and coil pack were replaced.
  
• It failed on the cat, but when replaced the C02 was down but the hydrocarbons were not, so the garage replaced the leads and coil pack.
  
• This got it through the MOT
  

Interim Period

• Since the MOT the idle when warm has been rough.
  
• I have since replaced the plugs but it made no diffeence.
  
• I have disconnected the battery lead for 2 hours to reset the ECU. It made no difference.
  
• Someone suggested putting a small amout of grease on the tip of the plugs (not the bit in the engine!) I have done this and it has made no difference.
  
• I noticed the garage only replaced 2 of the 4 bolts in the coil pack, I have replaced the missing ones but it made no difference.
  
• The idle has only been rough since the work was carried out.
  
• I did go back to the garage but they just said bring it back as they though it might be an air leak.
  
• I have checked but cannot find an air leak (not too sure what they were on about and to be honest I was not convinced and why suddenly do they think there is an air leak?)
  

Other Issue

• When the revs reach 2250 there is a juddering which clears at 2750. It is worse in the higher gears as the lower gears go through the range quicker.
  
• Is this connected?
  

Any help would be much appreciated as I am running out of ideas.

Thank you.

[SNAKEBITE]

I should have put that the car is a 1.8 Petrol.

Sorry...................