[panicman57]

I have a 2003 gmc Sonoma 4.3 with automatic trans for about a week now, when I start the truck in the morning it will run at about 2800 rpms for about 90 seconds to 2 minutes it them slowly idles down to about 2500 rpms.. them it drops quickly to 1500 rpms and finally down to about 600 rpms once I start driving at get to about 40-45 mph at about 1500 rpms and take my foot off gas it keeps running like the cruise is on sometimes it will slow down but most times it does not I have totally disconnected the cruise control I have changed maf sensor, tps sensor and idle air sensor has this happened to anyone else please help give me some idea where to look next tony

 

[Pikey]

Any service engine soon light? I am not sure if the 03 still had an iac

 

[panicman57]

no service lights or codes come up

 

[Pikey]

Maybe an intake leak. If you spray carb cleaner with straw around the intake and listen for rpms to increase you may find your leak

 

[panicman57]

already tried that no vacuum leaks

 

[silverado002]

Have you checked to see if the throttle plate is binding in some way or return spring is binding or weak?

 

[Pikey]

Clean the throttle body. Pull the idle air control (iac) out and clean the hole that it goes into. It may be a bad iac

 

[panicman57]

throttle body looks clean I can try to take iac out and clean that thanks

 

[Bdtoady22]

Anyone ever figure this out? Exactly what mine is doing

 

[RayVoy]

I'd disconnect the battery neg, and reboot the ECM

Leave the battery disconnected for 2, or 3 mins

 

[Motor City Rick]

When the motor idles at 600 rpm's, disconnect the IAC, ...let the motor get cold and see if the motor will idle high again. If the motor gives you a hard start, lightly press down on the gas pedal start the motor and see if the motor idles high. But before that, follow RayVoy's instructions, ...but leave the battery disconnected a lot longer than 2 to 3 minutes. There are capacitors in the ECM that will keep engine specs for a couple of hours. If you had a scan tool, it would be nice to get some data, especially the IAC count.