High Idle While Shifting/coasting

[sen2two]

My car idles pretty steady at 800rpm when at a stop. But while shifting gears (5 speed) or going into nuetral while coasting to a stop, the idle will rise to around 1500 or slightly higher and glhold there until around 5mph or a complete stop. Then go back to normal idle RPM.

Not sure what the issue is here. TPS is adjusted and IAC is decently new. Nothing else in on the TB as it is a 75mm Holley and a EGR Block off plate as well. No check engine light or other issues.

When I have tuned AEM EMS on other cars, this was a setting. I could set the high idle to be active or deactive at a certain MPH, load, and other thresholds. But I am on the stock computer and MAF as well. So I am unsure what may be causing this issue.

Any ideas?

 

[General karthief]

Run the codes? You can have issues that do not trip the light.
Check the sticky things for how to do that, you may already know, your ride ain't been converted

 

[a91what]

VSS sensor, it's part of the idle control circuit and tells the ECU when you are moving. I would check and see if it is connected.

Next step would be to check the switches on the clutch pedal, there are 2. one is the NSS, the other is a grounded circuit that tells the ECU that you have engaged the clutch.

I tune MS ems systems and use both of these circuits for a stock like idle control.

 

[General karthief]

Dogg gone it, I forgot about that
not really

 

[Mustang5L5]

I have my suspicions, but run the codes. It will help eliminate some of them.

Also, would help to know background of car. Is this an original 5.0 5-spd car? or was something swapped?

 

[TOOLOW91]

I was just about to ask if it was an auto swapped to 5 speed car with an automatic computer.