2000 Mercury Cougar

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
February 26, 2009.

Does the check engine light come on?

Mar 3, 2009.
It sounds like an Idle Air Control Valve (IACV) issue. I would try servicing it first and see what happens.

Mar 3, 2009.
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

Mar 6, 2009.