2.9 EGR Valve

4xFordFreak · #1 (**permalink**) 06-05-2007, 08:13 PM

How does the EGR valve operate on the 2.9? At cold start up should I have pressure on the sensing line on the EGR? When will there be vacuum on the vacuum line? I have a code for low voltage on the egr. the truck runs great for the first 40 miles then starts to stumble. Any and all help would be appreciated.

mrshorty · #2 (**permalink**) 06-06-2007, 12:03 AM

I find that the first step in diagnosing any EEC-IV trouble code is to identify which type of code it is. Was it a KOEO (hard fault) code, KOER code, or CM code? This can be important because a KOEO code (which is set with the engine not running) almost always has to be electrical. A KOEO EGR code wouldn't have anything to do with vacuum.

As for basic operation. The computer monitors the voltage from the PFE sensor (Pressure Feedback EGR). Above idle, the computer tries to maintain a certain sensor voltage via a pulse-width modulated signal to the EVR solenoid (EGR vacuum regulator). When the voltage is high (indicating high back pressure), the computer increases the duty cycle on the EVR solenoid to open it, and the EGR valve, more. When the signal goes low, the computer closes down the EVR solenoid and allows the EGR valve to close.