It will help if you include the engine size and fuel type (carb/FI). A few questions and a few visual checks to start. When is the last time you changed the fuel filter?... if there is sediment in the filter it can be sucked up during acceleration (causing the motor to lean out...increasing RPM) and settle back when the engine is shutoff. Check the fuel cap for proper ventillation(seals not cracked/broken/holes plugged), if the motor is carborated then check all vacuum lines, and remove the float bowl(s) and check the float(s) for smooth unobstructed full movement, also check the throttle return spring for sticking / binding. Also remove the accelerator pump(s) and check for damage or blockages. If it is FI you may have a/some dirty injector(s)
_________________ 2000 H190 5.0GL
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