2000 Mercury Cougar idle

[quote:15327c268c="james79neff"]Engine Performance problem
2000 Mercury Cougar 6 cyl Two Wheel Drive Automatic 100000 miles

when i start the car the rpm jump to 2000 then fall to about 900 rpm the n engine starts shaking while idle jumps then dies restart car happens agin. unplug maf sensor engine smoothes out. replace maf sensor w/new one same problem. unplug egr valve vacum smoothes out . what could this be[/quote:15327c268c]

does the check engine light come on?

It sounds like an Idle Air Control Valve (IACV) issue. I would try servicing it first and see what happens.

The Exact same thing was happening to my car.
the problem with this type of issue is that there is a lot of intereaction between the functions of alot of the sensors. In effect a failure of one item can look like it is caused by another, I disconnected my EGR valve and plugged the line at the hose. I also tapped on the valve to try and get it to return to the relaxed position. the car ran fine until I plugged the EGR valve back in. Replaced Valve and car has ran fine for 2 weeks (knock on wood).. The CHECK ENGINE LIGHT would not come on right away. I got two codes P0171 and P0174. which are LEAN BANK 1 and LEAN BANK 2