'94 EGR problems

[steyr911]

I have a '94 Grand AM GT 3.1L engine. when i drive it at highway speeds, or if i redline it, a service engine soon light shows up. I got the diagnostic testing done, and the mechanic said the EGR vavle was bad, but he also said that since the EGR is non-essential, it was pointless to replace it for the 300+ dollars it would cost. the engine light is really annoying, so one day i took the valve apart, and i found a gray sludge stuck in the ports to the egr, and in the hose leading to the intake manifold, but none in the hose leading from teh exhaust manifold. i cleaned it out, and while it seemed like it helped i still got the light every now and then, so i took it apart again, and the sludge had returned! where can this sludge be from? i dont want to buy another egr valve if the engine is just gonna clog it up agian. can anyone help me out here?
thanks!
Dom

[davyrocket1967]

Try cleaning out the throttle body really good, make sure all the carbon build up is out. Hope that helps

[Knifeblade]

Well, sort of like Davy is stating, the throttle body clean is a worthy try. The EGR vents exhaust gas through the exhaust manifold back into the valve cover, where the gases find their way back into the air-fuel mix to get re-burned. That is a very simplistic view of how it gets done. One major reason for your sludge is A] too rich a mixture or B] the valve or the ported vacuum feed to it is getting plugged and allowing the sludge to build up.

[Knifeblade]

http://www.autozone.com/servlet/UiBr...3d800e5537.jsp