Lumina APV engine problems

I have a 1995 Lumina APV and I am having engine problems with it. When I get up around 40 miles per hour and again around 60 miles per hour I have a bad miss in my engine. Once I get above these speeds the engine seems to level out and run fairly smooth. I thought it was a gas problem so I switched gas stations and added some injector cleaner. That helped some but I am still having a miss from something. I have the 3.8 litre engine. Any ideas on what may be causing this?

did your check engine light come on. If so, take your van to Auto Zone or Advance, and have them check the codes for you (they do it for free) and report back with the findings.

did your check engine light come on. If so, take your van to Auto Zone or Advance, and have them check the codes for you (they do it for free) and report back with the findings.

I get a warning light that says "Service Engine Soon" but it comes and goes, does not stay on all the time.

as long as the light came on it stored a CODE FOR WHEN IT DID SO HAVE IT SCANNED AND THE CODE WILL STILL BE THERE. sorry caps locked lol.

I finally figured it out. It turned out to be bad plug wires. I had them replaced and three of the six were cracked. End of problem.