Engine miss fire

[98 gmc 4x4]

My trucks got a missfire when it warms up only after the thermostat opens it does it and only up to 2000rpm after that it is fine. The miss is like if some when hit a kill switch and turned it back on only does it under 2k like putting threw town and roll in the gas a little bit It will studer the. If I apply more throttle to bring it above 2k it goes away any idea all spark plug wires have good conection and the rotor and cap are fairly new. Thanks for your help!

 

[loosebearing a nut]

When going to closed loop ecm is sensing something is not right. Are you getting a service engine light?
If so scan it. Maybe cts/coolant temp sensor located beside the thermostat housing. May need to clean the maf sensor.
Maybe a vacuum leak . I could go on but will not ..take it to auto parts for a free scan .
See what codes are should have one or some ...a scan is your friend .
Keeps from wasting money and time ..best mechanics have to scan ..some guess .

 

[SAATR]

It would really help to know whether or not your CEL is on, and what DTC's are being set. It has already been said, but getting this information is a crucial step in finding out what your issues may be.

 

[98 gmc 4x4]

Ok sorry guys. Have no codes for that just my o2 sensors bc of hollow cat. That is it