I did a full service on my 2003 ford focus today - oil, filters and plugs.
I did a test run and the car was running lumpy and engine warning light come on! I checked all the spark plugs again and I realised that the rubber gromet from the spark plug socket was on the last spark plug. I took it off and the cars running fine now, BUT the engine warning light is still on. Can anyone help?
Mine (04 Focus) came on last week too - apparently the 4th cylinder was misfiring. Plug lead was cracked so they changed that and the spark plugs. Still not right, replaced coil pack, all better.