I have a 1994 Chevy S-10 Blazer that has had a tune up this month, November, and experiencing surging when I have foot off the gas pedal and dieseling when I turn the engine off. I have not changed the timing belt in more than 5 years and the fuel filter in 1 year,could this be the problem?
Neither of these items is the cause, even if both were to be in need of replacement.
It sounds like whoever did your tuneup knocked a vacuum fitting or electrical connector loose.