Engine surging

[ThunderChicken]

I just started noticing this. It has gotten a little colder here in the Ozarks and I have found that my VX is over revving after I drive about 30 miles. When I start to slow down the RPM's stay up around 1,500, I dont know why it want go down to around 800-1000 RPM like it is supposed too.

I have poured in some carb/injector cleaner and it seems to work a few days and then bam, it starts doing it again. Today I poured in some Heet and it didn't seem to help.

Also around 40 miles per hour the engine surges until I get up to around 50 and then it stops. Could this be connected or is it two seperate things?

I don't understand whats going on.

[Andrey]

Check your fuel filter and intake gasket. Our engines are known for bad " vaccum" leaks on intake gasket. This might contribute to your condition.

[Tone]

Idle control valve mounted on the throttle body could also cause this - it gets gunked up over time. It is held in place with 2 Torx screws and can cleaned with carb cleaner and checked for easy movement. May also want to take intake tube off and spray intake cleaner around the butterfly as gunk builds up there and could be preventing it from closing all the way. TPS could also cause this but the intake gaskets are notorious for this. Clogged fuel filter is unlikely to cause this behavior.