My EGR valve occasionally malfunctions and the computer throws the "service engine soon" code, which allways turns off when I restart the car. It used to happen only when the engine was fully warmed up (+210) and I was under the impression that the EGR valve didn't operate until the car was warmed up. The car has been throwing this code occasionally at much lower temperatures recently, but still turning off when I restart the car. Could this still just be the EGR or do you guys think it's something else?

 

What code is the PCM setting for the EGR - there is more than one? A more basic question.... what year is your car? There is a significant difference between the OBD-I and OBD-II diagnostics used on the LT1. Without knowing the year of your car, its harder for people to provide you with accurate help.

Why not add a "signature" with basic info about your car, like year, model, tranny type and any major mods?

 

I don't know what the code is - I only know it's related to the EGR valve.

 

There's one code (DTC 27) for a faulty electrical circuit on the EGR vacuum solenoid. There's another (DTC 32) for lack of EGR flow. On the 93-95 OBD-I cars, the "flow" diagnostic is not very sensitive, and many people are able to completely delete the EGR system without setting a code. But if the EGR solenoid circuit is screwed up, its 100% that you will get the code (DTC 27).

Lack of flow can be caused by a low back pressure exhaust system, faulty EGR valve, plugged EGR solenoid, leaking vacuum lines from the manifold to the solenoid and from the solenoid to the valve, plugged EGR passages in the intake manifold, broken riser tube from the passenger side exhaust manifold to the back of the intake.

Courtesy of Shoebox:

http://shbox.com/1/egr1.jpg