Van is idling very rough until it warms up; after that it seems to run fine. Check engine light is on, pulled code 558 "ER vacumn regulator circuit failure". Chilton manual gives no help. I have put in a new EGR valve, and checked all the vacumn lines for wear. Any ideas?

 

Check the actual sensor on top of the EGR. If it's working look for the bank of vacuum relays. You're looking for the round one, it's the one for the EGR. It's failed, either open or closed (given the symptoms it's open). When it allows vacuum to the EGR it opens and dumps exhaust into the engine, what is happening is that it's open all the time and causing a rough idle.

 

Thanks Pfogle. That gives me some places to start; I'll get under the cowl this weekend and check it out.