Bad EGR
Thread Starter
|
Cross-Country
Joined: May 2019
Posts: 58
Likes: 3
Bad EGR
I recently did a vacuum test on my 84 460 and when the vacuum line is hooked up to the EGR the needle bounces between 14 and 18 at idle. Once I disconnect the vacuum to EGR, and plug the line, the gauge steadies out at 20 or so and engine runs smoother. Vacuum gauge is hooked to manifold fitting while doing this. I suspect the EGR is bad, would I be correct?
Logistics Pro
Joined: Jun 2017
Posts: 3,952
Likes: 509
From: Edmond, OK
You can remove the EGR valve and use a hand pump to check it for actuation. If it doesn't actuate fully sometimes you can clean it with carb/choke cleaner and get it to work properly. My bet is that your EGR valve is actuating but once it does your timing/carb settings aren't right to burn the EGR gases properly.
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
I recently did a vacuum test on my 84 460 and when the vacuum line is hooked up to the EGR the needle bounces between 14 and 18 at idle. Once I disconnect the vacuum to EGR, and plug the line, the gauge steadies out at 20 or so and engine runs smoother. Vacuum gauge is hooked to manifold fitting while doing this. I suspect the EGR is bad, would I be correct?
NO you are not correct. The EGR essentially creates a vacuum leak. Symptoms of a vacuum leak surging idle because of a surging or bouncing manifold vacuum.
Most all the EGR valves used in this era were assisted in other words they required exhaust backpressure to function correctly as it assisted in their opening. Putting a vacuum gauge with a pump on them will tell you nothing as they were not airtight and did not just rely on vacuum to actuate them. So if you have pulled the cats or modified the exhaust from stock the EGR will not function as designed or calibrated.
Moderator
Joined: Jan 2001
Posts: 56,973
Likes: 2,731
From: Virginia
I recently did a vacuum test on my 84 460 and when the vacuum line is hooked up to the EGR the needle bounces between 14 and 18 at idle. Once I disconnect the vacuum to EGR, and plug the line, the gauge steadies out at 20 or so and engine runs smoother. Vacuum gauge is hooked to manifold fitting while doing this. I suspect the EGR is bad, would I be correct?
1st test to try, leave the vacuum hose off and put a screw in it. If it runs fine with no ill affects, drive on. If you get some pinging in certain driving conditions, you may need to hook it back up properly or go to plan B. Plan B can be can or worms, we will wait on that.
Thread Starter
|
Cross-Country
Joined: May 2019
Posts: 58
Likes: 3
The exhaust has not been modified. I can see the EGR diaphragm slowly move when vacuum line from engine is hooked up. When I disconnect this line and plug it, my vacuum gauge (non-pump style) needle steadies out and the engine runs smoother.
Thread Starter
|
Cross-Country
Joined: May 2019
Posts: 58
Likes: 3
One thing I see, you should not have manifold vacuum to the EGR. Like you have found out and the others mentioned, the EGR opening at idle will foul the engine up. So what they did is only open it when the rpms were higher, and only opened it when the engine was fully warmed up. It should only be hooked to a ported vacuum source, there should be a special port on your carb with vacuum on it only when the throttle is opened. And it also should be hooked to a gizmo threaded into the water jacket that only allows ported vacuum when the coolant is hot enough.
1st test to try, leave the vacuum hose off and put a screw in it. If it runs fine with no ill affects, drive on. If you get some pinging in certain driving conditions, you may need to hook it back up properly or go to plan B. Plan B can be can or worms, we will wait on that.
1st test to try, leave the vacuum hose off and put a screw in it. If it runs fine with no ill affects, drive on. If you get some pinging in certain driving conditions, you may need to hook it back up properly or go to plan B. Plan B can be can or worms, we will wait on that.
I believe this answers the issue. The EGR vacuum line was routed from manifold vacuum to the VCV and on to the EGR. I will remove the line from manifold vacuum, and hook it to the ported side of Holley carb (4160) and see how it does.
When completely disconnected and plugged, it runs great.
Logistics Pro
Joined: Jun 2017
Posts: 3,952
Likes: 509
From: Edmond, OK
If that's the case are there emissions tests in your area? If not then just leave it plugged. If there are sniffer emissions tests you might have to get the EGR valve functioning correctly to pass a sniffer test since it's designed to reduce NOx.
Thread
Thread Starter
Forum
Replies
Last Post
sundaydriver
1987 - 1996 F150 & Larger F-Series Trucks
6
Apr 26, 2007 05:36 AM
ssanto
Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W)
1
Dec 6, 2006 09:38 AM
compaddict
1987 - 1996 F150 & Larger F-Series Trucks
5
Jul 21, 2005 08:43 PM
