2004 Ranger 2.3L manual
My complaint is that the engine speed is not decreasing enough between shifts, this is making revmatching difficult. I have a hypothesis that the PCM is commanding the idle air control to stay open in between shifts to prevent hydrocarbon emissions when the throttle snaps shut, similar to the purpose of a dashpot on the throttle body of 90's cars. In 2011 I attempted to fix this by having the local Ford dealer update the software to the latest at the time, but this did not improve the issue. I am inclined to say the software they installed was dated 2010. While doing maintenance on my truck recently I have been inspired to look into the issue again. I have tried disconnecting the IAC on a test drive to see if the idle would drop faster between shifts but wasn't able to get a conclusion on this because it would not stay running with the IAC disconnected. This did however tell me that the IAC is closing enough to 0% and that it is not sticking or excessively dirty.

I hope to get a scanner to read what the PCM is actually commanding the IAC to do between shifts, but until then I wanted to open a discussion about the issue. Is there a setting in the PCM that Ford can turn off? For example, an "idle follower" setting like General Motors has?


Reference this TSB 5510 for the 4.0L engine regarding this issue which recommends updating the software to fix the issue. But this is on a different engine than mine.
2004 ford ranger Technical Service Bulletins

 

Yes on manual transmission there should be a delay in the RPM dropping when changing gears, this is an emissions and MPG routine.
RPM also will not drop below 1,000 until speedometer is below 5mph

 

No. You are stuck with some dashpot during shifts. It is calibrated by the manufacturer during development and a Ford dealer does not have access to the setting.

At closed throttle, verify that the Throttle Position Sensor input to the PCM is somewhere between 0.53 and 1.27V. A closed-throttle TPS reading that is higher than 1.27V could fool the PCM into thinking that the TPS is in part-throttle "pre-position mode" and that might possibly make the RPM hang/flare worse.