EGR valve problem
Thread Starter
Instructor
Joined: Nov 2013
Posts: 166
Likes: 8
From: Acworth GA
EGR valve problem
1978 Standard, probably stock engine.
Lars rebuilt my carb for me and set the idle speed and idle adjustment screws. He had set the idle at 800 I believe. When I put the carb on my engine it was running about 1200 after warming up and 1500 cold.
So it sent me off on a search for the vacuum leak(s). The first one I found was the EGR valve. Now I know that the engine does not apply vacuum to the EGR valve at idle. The diaphragm was busted so not only did it leak but it did not work. When I put the new on and was driving about 40 mph, I notice the engine making a gurgling sound or a sound like you would hear when the choke is stuck and the engine in hot. I went back to AutZone and asked the guy about it as I figured it was a defective valve. He said that I really should test it with a vacuum gauge and vacuum pump. So I bought one as I did not have either one.
First I test to see how much vacuum was applied at 2000 to 3000 RPM. It started at 5 inches and went to about 12 inches at 3000. So I then disconnected the vacuum hose and connected the pump. Started the engine, increased the RPM to 2500, engine was smooth, pumped in 10 inches of vacuum and the engine gurgled and slowed down. https://www.corvetteforum.com/forums...lies/crazy.gif
What is the downside to just not hooking it up? It seems that my engine doesn't like it but it's designed to be there.
Does anyone have any experience whit this thing or know what I'm talking about?
Lars rebuilt my carb for me and set the idle speed and idle adjustment screws. He had set the idle at 800 I believe. When I put the carb on my engine it was running about 1200 after warming up and 1500 cold.
So it sent me off on a search for the vacuum leak(s). The first one I found was the EGR valve. Now I know that the engine does not apply vacuum to the EGR valve at idle. The diaphragm was busted so not only did it leak but it did not work. When I put the new on and was driving about 40 mph, I notice the engine making a gurgling sound or a sound like you would hear when the choke is stuck and the engine in hot. I went back to AutZone and asked the guy about it as I figured it was a defective valve. He said that I really should test it with a vacuum gauge and vacuum pump. So I bought one as I did not have either one.
First I test to see how much vacuum was applied at 2000 to 3000 RPM. It started at 5 inches and went to about 12 inches at 3000. So I then disconnected the vacuum hose and connected the pump. Started the engine, increased the RPM to 2500, engine was smooth, pumped in 10 inches of vacuum and the engine gurgled and slowed down. https://www.corvetteforum.com/forums...lies/crazy.gif
What is the downside to just not hooking it up? It seems that my engine doesn't like it but it's designed to be there.
Does anyone have any experience whit this thing or know what I'm talking about?
Last edited by Rich123; Aug 31, 2015 at 04:42 PM.
Thread Starter
Instructor
Joined: Nov 2013
Posts: 166
Likes: 8
From: Acworth GA
I did finally idle it down so I could drive it but I know there is still a vacuum leak. When Lars set the idle his setup did not have leaks, so mine must be leaking. I adjusted the idle adjust screws the first time he sent the carb to me. When I sent the carb back for him to look at what I thought was a problem he said the idle screws were all messed up. Well they would be if I'm adjusting to compensate for a leak. So I did not mess with them.
