Fast idle
Cargo Master
Joined: Aug 2021
Posts: 2,258
Likes: 742
From: Maryland
Could be a few things, including timing, vacuum leaks, dirty Idle Air Control valve, or the throttle cable hanging up at the firewall.
There is a throttle plate stop screw that gets mistaken for idle adjustment, but it's actual function is to keep the throttle plates from closing inside the throttle body too far and getting stuck.
If you disconnect the throttle cable from the throttle body linkage, and manually open the throttle, the throttle plates should spring closed when you let go.
On cold starts, these trucks idle at around 1500 RPM for about 15 or 20 seconds, then drop down to around 750 over the next minute or so.
There is a throttle plate stop screw that gets mistaken for idle adjustment, but it's actual function is to keep the throttle plates from closing inside the throttle body too far and getting stuck.
If you disconnect the throttle cable from the throttle body linkage, and manually open the throttle, the throttle plates should spring closed when you let go.
On cold starts, these trucks idle at around 1500 RPM for about 15 or 20 seconds, then drop down to around 750 over the next minute or so.
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