Help with 4.3 vortec

I have a 1995 k1500 pickup with a 4.3 Vortec Z code engine. Does anyone have a fix if the engine runs just fine when it's cold. After the engine warms up it jerks at highway speeds. If I keep the RPM above 2000 RPM it runs fine. The codes I got were the running rich code. So far I've changed the EGR valve and the O2 sensor. Any ideas?

Engine Coolant Temp sensor may be bad. Have it scanned to see what temp it is reporting.

//2000CAYukon

You might have a bad fuel pressure regulator. It's the spider dealie in the intake, i'm pretty sure the regulator isn't serviceable separately.

If it is CPI, the regulator can be replaced after removing the upper intake plenum and removing the "spider" injector assembly...the regulator is mounted on the firewall side of the base that holds the injectors...about a 2-to-3 hour job. They cost about $45. Install a fuel pressure tester and get readings when the key is on/engine cold, then start it and warm it up and rev it to the problem RPM range and note the pressure. Should be at least 60 psi with key on.

Another idea might be the poppet valves sticking open...they're the ends of the hard plastic tubes on the "spider" that snap into the cylinder heads. Run a good fuel system cleaner liek Seafoam or have the injector spider assy cleaned.

good luck!

This engine has a throttle body. Does this still apply?