It's missing all the time and it gets worse under heavy acceleration, There are no engine codes. The plugs were replaced last summer and I did check the plug wires with a little tester I bought from a local parts store and they seem to be ok. I also replaced the fuel filter a few months ago. The car has 170,000km or 102,000 miles. Any ideasbongobobny said:I assume you mean your engine is intermittantly misfiring... Is your Check engine light on? Any codes?? Is it missing at idle, all the time, or under heavy accelleration??