After reading an article in Chevy High Performance, I question the EGR valve in my 85 IROC. I checked the valve, which seems to be stuck--at least there's no movement when pushed. Also, when cold, the car backfires a bit. Anyway, with the vac line blocked off, the idle is smoother and there's really no bog. Time to replace?

JamesC

 

You can use a hand-held vacuum pump to check the EGR valve. Connect it to the egr and start pumping. On the bottom of the
fat round part of the EGR there are large holes. You can stick your finger inside and feel the diaphram lifting and lowering when vacuum is applied and removed.

If the EGR valve doesn't hold a vacuum, the diaphram is leaking and valve should be replaced.

If the vacuum holds, but the diaphram doesn't move, it's stuck. Replace valve.

With eng idling, manually raise the diaphram, eng should die or almost die. If eng RPMs don't change the EGR passages are plugged.

If you suspect the valve is not closing all the way. Remove valve and try to blow thru it.

 

Which CHP did you see that in? I got my latest one last week, and I must have missed that article.

You can follow this flowchart for diagnosing your EGR:

 

Thanks for the replies. Vader, the article, "Stumble RX," is on page 78 of the latest issue.

JamesC

 

Hey, Guys,

According to my shop manual, there are several types of EGR valves for my 85 IROC LG4 (mine is apparently the negative feedback type), but my GM parts man says there's only one part number, changed from 17110476 to something else. So does the type of EGR valve matter?

JamesC

 

I guess I missed that article on the fisrt pass. The bad part about the diagram on page 80n is that is showed a standard port-type EGR valve (they also showed no atmospheric vent on the EGR solenoid). You have a N-type EGR, which requires an absence of exhaust pressure to allow the EGR main diaphragm to get vacuum from the pilot valve:



I have no clue as to the correct new part number.

 

How do you know if someone may have put the wrong egr on your car? Positive versus negative??

thanks,
phil

 

Phess,

If the valve is original, or an AC/Delco or GM replacecment, it should have either an "N" or "P" stamped on the top of the diaphragm spring cover.

 

Its not a GM