ray1979

Quick backround. 88 corvette auto 24k miles I was having a issue of knock counts and spark retard on part to full throttle. Check the knock circuit all looks good. Today I when to check the egr valve and egr solenoid. I applied vacuum to the egr valve and it held vacuum I also heard it moving. Then I checked the solenoid as per the manual. then I tested the vacuum on the solenoid. The service manual states that the solenoid fails however when I apply vacuum it holds then releases as I think it should. Now here is the part I need help with. I then go to start the car and it would hardly start. Once running the idle was bad I give it gas and it smooths out. then back to a bad idle.
before this the car ran and idled very well. Not sure if applying vacuum to the egr stirred things up. It is not setting any codes

MrWillys

Sounds like a vacuum leak?

ray1979

Possibly but all the vacuum lines are good. And the egr holds vacuum. Unless the solenoid is letting vacuum through. I will try capping off

cudamax

Is the EGR opening While its Idling like crap pull the vacuum and push it in to try and seat it. As a Diagnostic tool only Get a empty tin can bottom or a coffee can bottom and remove the EGR and make up a plate to fit on the bottom of the EGR and block it Sometimes the nipple of the EGR has to go

65Z01

Don't guess at quality of manifold vac, put a gauge on it to see what is the actual value.

ray1979

Did some more testing the solenoid passes the test found out when I applied vacuum to the egr it was stuck fully open. I blew into the valve and it seated fully. It will release on its own as long as it not fully open. maybe it is carboned up. once seated the car idled perfectly I will remove it for cleaning. I might just replace it as the acdelco part is only $52.00. the part number on the valve is 17086078 I looked it up and it shows 88 corvette can anyone confirm that as the original part?

cudamax

UR Welcome and u can take those off pull the sol and soak em