1999 Isuzu Trooper, high idle

[hellokit]

It sounds like the idle air control valve (iac) is full open. Did you set the iac pintle (the part that moves) to the position the manual says to? If you didn’t get the instruction, go to an auto parts store and ask to look at the instructions on an iac valve. Also, the iac valve may not be getting a signal, or power, it should. You need a digital voltmeter, or a scan tool, to check for those voltages.