Chevy & GMC Vans

anybody get code
po174
p0171
p0758
p0300

I started getting these together, starting to think its computer, seams to come on strong and then go away, seams to by random missing and yesterday would not shift out of 2nd gear until i turned off and on again. I recently replaced cap and rotor and spark plugs

I'd start by looking at the first two, they could lead to the second pair of codes you have. Could you have disturbed something while replacing those parts? Vacuum lines when old are easily broken or dislodged, time to dig deeper.

Diagnostic trouble codes exist to tell you what's wrong with the engine, so you need to look them up.
This is a great site to use. Just follow the troubleshooting there:
https://www.obd-codes.com/

Let us know if you run into trouble.

Also, please do not hijack old posts. I moved your question to its own topic in the Engine section. Thanks.