Lined Trimmed

Any ideas on fixing a Homelite ST155 line trimmer that will not stay running?

It surges. I can start it and it will run fast then slow then fast then slow without me changing the trottle position. It will do this for about 5 seconds and then die. It will start right back up and do the same thing. It has fresh gas/oil and a new spark plug.

Toss it and spend just a little more on an Echo or Stihl trimmer from a reputable dealer that's not big box. You'll pay a bit more, but get much better, free service.