Surprising Fault!!

Hi everyone

My partner's mk1 Focus has been a little down on power recently. Not drastically. But noticeable when, for example, pulling away quickly at a fast junction. There has been a noticeable judder and lack of engine response.

I finally got round to having a look at the plugs and leads, as a starting point to identifying the problem (even though I knew they are fairly new). I did not get far before I noticed one of the leads not sitting properly on the plug. I pulled the lead out and to my surprise found a reasonable size stone by the plug! As shown in the photo.

The car has fairly recently been in the local Ford dealership for a cambelt and waterpump change. This problem has been happening roughly, we think, since we got the car back from the garage. I am at a total loss as to how that stone could have got in there. I might be being overly cynical, but I have started to think that perhaps it was put in there on purpose, as it would have to be a pretty elaborate accident. The aim being that Mr or Mrs X would return to the garage a short while later (the problem not being so severe as to notice it and return straight away) and they would easily be able to charge an hour's labour for finding the fault and another hour for putting it right.

If my cynical suspicion is correct, then this is a warning about Trowbridge Ford dealership. However, I hope that I am talking nonsense and wonder if anybody else has found foreign objects like this? Which would make me think this is a more plausible accident than I currently do.

Thanks for reading, Pete.