Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Hello and welcome! My name is ***** ***** I can assist you with your question. How do you know you have back pressure problems? Have you checked exhaust back pressure? If so how did you check this and what are the readings?
Does the engine run ok? Does it have plenty of power under a load?
And how do you know the EGR valve is not opening?
That itself.. even it was the problem, has nothing to do with back pressure. If you had too much back pressure, the EGR valve would open up too early.
The EGR valve should not get full manifold vacuum.
And just because it fails the NOX readings does not mean the problem is "only" the EGR valve or EGR system.
There are other things that can factor into high NOX
No, the EGR valve does not operate at idle.
The EGR valve should not operate under heavy throttle applications either.
The problem is not your EGR valve.
Above in your first post you said the engine does stall out when opening up the EGR valve at idle.
So, yes, the engine should stall out when the EGR valve is opened up at idle. This means the EGR ports are clean.
Again, the EGR valve and system is not going to be the issue.
Ok, then yes, that is a problem. it sounds to me like the EGR ports are plugged up
Hello and sorry for the delay! Now that I understand your question better because you explained it to me in more detail, it sounds like the EGR ports are restricted. Start by cleaning the EGR ports and then retesting the system. Let me know.