Silverado 6.0 Engine RPM "Hangs"

[Blazin72]

This is a problem that is really starting to get annoying and seems like it's occurring more frequently. Any time my truck is moving faster than about 10 mph it wants to keep its current speed and RPM when I let off the gas. If I push the clutch in the RPM drops for a second then rises about 1000 RPM above what I was cruising at for several seconds then slowly starts to drop off. I can coast in neutral at 60 or so and let the idle settle down then hit the gas and the RPM rises back up and holds again for several seconds before dropping back down. It does not do this 10 mph and slower, including while it's stopped. It's almost like the cruise control is trying to remain on or turn itself on even when I have the switch on the signal lever in the off position. The accelerator and cruise control cables both appear to move freely and I haven't found any vacuum lines on the engine (I don't think it's vacuum related anyway). It seems to do this once the engine has reached operating temperature and when the engine has been heat soaking after running or sitting in the sun all day.and doesn't seem to do it all during cooler temps.

It was suggested to replace the IAC and/or TPS. I did and neither fixed the problem.

Any ideas? I'm baffled.

The truck is a 2000 Silverado 3/4 ton with a 6.0 and five speed manual.

[Johnny Cetane]

Have you tried removing the throttle body and cleaning it? The older ones used to get pretty gummy. I'd bet that this is your issue.