Hi, I have a 99 taurus with 140k miles, 3.0L SOHC. The car has a choppy idle while in gear that feels like the gears catching (not like normal idle stutter).
It will sit and bounce between 800 and 1000 rpm in quick 2 second periods. Also, there is a vibration through the break petal that feels like the engine is pulling on the transmission.

I have checked the IAC and the EGR and both seem to be working fine.
To test if it was a throttle body component, I put the car in gear and used my left foot to break while slowly applying gas. Even as the RPMs climbed, the shudder of the engine that felt like first gear was trying to engage continued so long as the break was held down. During normal driving, the car accelerates smoothly and there is no missing or catching through the upper RPMs.

This makes me very concerned that there is something seriously wrong in the transmission around the torque controller or some similar high-dollar part that requires professional attention. Any thoughts?

 

Engine warning light on? ATF at proper level? My experience with the Taurus tranny is they work great, then without warning, torque converter dies. tranny shop claims this is a Ford weak-spot. the un-even idle may be a sensor that is not bad enough yet to trip the light.

 

Engine light is on, code refers to the EGR, but is most likely a failure of the DPFE. I pulled the EGR and made sure it was opening and closing with vacuum, cleaned it and put it back on to no avail. Just got through changing the transmission filter and replacing half the ATF. I might eat the cost and get a new DPFE to see if it clears the code, if not, its double that cost to get a new EGR.