After about 15 minutes of driving my tachometer starts to jump up and down and the engine sputters a little. It does this for about 5 minutes then the tach goes out and the engine runs normal again. My check engine light has come on several times. I've taken it in twice and had it hooked up and the mechanics said they can't find anything wrong. Anybody have any ideas

Thanks

 

sounds like a bad ignition coil,but check all of your connections first