Ok so I have been trying to figure this out for a couple of months now.
On start up the engine runs roughs, no check engine light. Then once I start driving it drives really smooth. But as it gets to about 45 to 50 mph the engine starts running really rough again and didn't wanted to go. Once I push the pedal down all the way the engine will slowly move and invest its past 50 it runs great again....

This is driving me crazy. Any help would be great
Thank you in advance

 

Maybe a tune-up is in order? What have you done to attempt to fix it already?

 

Start with the basics that don't cost anything.

Scan for codes even though there's no CEL.
Compression test on all cylinders. Good time to inspect the spark plugs too.
Fuel pressure, including leak-down.
Check all plug wires for proper resistance and cracks in the jacket and/or shock boots.
Pull the distributor cap and check the rotor and all 7 contacts for carbon. Also check for carbon traces or cracks in the cap.
Check all ground wires and clean the grounding surfaces. Replace as needed.
Thoroughly clean the throttle body.

 

I put cap rotor wires and plugs in about 8 months ago. All properly gapped

 

When did this problem start?

 

About a year ago. I was able to temp fix Thomidis by putting premium gas in. But now that's not working either.

 

Ever figure it out mine is doing something similar

 

Just had a chance.to work on it yesterday. ,hanged the cool, rod, and cleaned the injectors. Seems to be running g better

 

Fuel Pressure at the rail?

 

I don't not have a gauge to test it was. So I don't not know.

 

Have you checked/cleaned your throttle body and airbox/filter? Replaced the air filter?

If you're still having issues and want to check fuel pressure, you can rent a tester from AutoZone or Advance Auto.