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Discussion Starter #1
I have a 91 Deville. It failed Vehicle Inspection for high NOx.
Spec is about 700, I'm at 850 or so. Bad odor from tailpipe.

My EGR valve doesn't appear to be working properly. I have good vacuum to the soloenoid. The computer is powering the valve at idle, closing the valve. If I unhook power, the valve opens, but I get just a little vacuum out of it. Not enough to open the EGR valve. If I connect the vacuum directly to the EGR, it opens fully and makes the engine run rough (as expected). I can hear vacuum leaking, so I assume I have a bad diaphram in the valve.

EGR valve part number is 17091120. Autozone website says this can't be checked with a vacuum pump. Anobther thread says you need exhaust pressure to help it open.

Computer doesn't appear to try to open the EGR when I rev it (in park).

How do I determine if I have a bad EGR valve, vacuum valve, or something else? Isn't the valve definitely bad if it had a vacuum leak?
 

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2005 CTS-V, 1994 Infiniti Q45
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It sounds like its clogged....... Have someone accelerate the engine slowly, and ending at ~2500 rpm.... You should feel the valve flutter and then it may open (not sure if your setup works exactly like mine)..... Although, it may not do any EGR unless your at cruising speeds or something along those lines......

Most of the time the valves dont fail (its possible though), but its more likely clogged.....

Its possible what your describing is NORMAL (as EGR operation sounds very much like a vacuum leak), or it could be bad....

Bottom line.... Id just get in there, take off the valve assy, and if its clogged (99% sure it will be to some degree, probably all the way if its never been done....) ,clean it out...... Reassemble and then test again.....!
 

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Discussion Starter #3
elwesso said:
It sounds like its clogged....... Have someone accelerate the engine slowly, and ending at ~2500 rpm.... You should feel the valve flutter and then it may open (not sure if your setup works exactly like mine)..... Although, it may not do any EGR unless your at cruising speeds or something along those lines......

Most of the time the valves dont fail (its possible though), but its more likely clogged.....

Its possible what your describing is NORMAL (as EGR operation sounds very much like a vacuum leak), or it could be bad....

Bottom line.... Id just get in there, take off the valve assy, and if its clogged (99% sure it will be to some degree, probably all the way if its never been done....) ,clean it out...... Reassemble and then test again.....!
Opening an EGR valve at idle will almost kill the engine. I did this with direct vacuum, and the computer raised the idle, etc. to compensate.
With this, I assume the ports aren't clogged, but it's worth checking anyway. I just used up my free retest, so now I have to pay $39.95 again. I want to make sure I fix it this time!

Should the EGR valve open fully if I disconnect the electrical connector the the vacuum valve?
 
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