I've had this issue for awhile but decided to post because Ive heard different opinions on other forums. Example: Im traveling at highway speeds and come to a red light. I let off the throttle and put the truck into neutral. The tack goes down below 1k RPM to 750 then bounces up to 850-900 a few times then settles back down to 750 and stays there. I do not have a programmer but I have an Arson II (No modified cascade valve). Is this what other manual transmission guys see as well?

 

Can you hear the engine doing this, or is it just tach?

 

It could be the modified FCA causing this. It's possible. They can do strange things.

 

My truck has done this since new, when it was stock and now with a Smarty programmer and modified CP3. I consider it totally normal and not a factor..

 

Mine holds about 850 until I get below a certain speed, it is to improve the braking and steering power.

The bouncing is probably the ECM trying to accommodate for the 90's and modified FCA as well.

 

I don't think my truck is tuned, it has a new FCA, and it bounces like that. I have not paid any attention to the listen to see if engine is actually going up and down.....but I think it is. Also if I'm running around 25mph and take it out of gear, the rpm stays up a little and then drops to idle as I apply brakes. Thought it was just the engine computer.

 

I figured it might be the FCA or the truck is dumping left over rail pressure