almost a 911, tranny or idle??

[ryf]

my 94 xlt just decided today that at idle it would start surging, feels like the torque converter was catching on and off, but there is a loud howl from under the hood, but at idle the truck literally moves up and down its better in nuetral, but I can't tell if its the tranny reacting to the motor or the motor reacting from the tranny, I've read about the IAC, but I what I read sounded like rough idle or lope, not full on truck moving up and down...

I checked my trany fluid, looked ok, the truck runs up and down the highway fine, just basically the longer you sit at idle, the worse it gets, any ideas?

 

[ExplorerDMB]

Check for a vaccum leak. Had a car today that was kind of stumbling on it face, and well - it was a vaccum leak. You could hear it with the hood closed. Anyway -- I would suspect a vaccum leak. Your transmission usually doesn't cause a rough idle.

-Drew