EGR issues
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
I do see now that the WOT valve actually shunts vacuum at Wide Open Throttle.... Hmm
Originally Posted by Ford Factory Manual
EGR SYSTEM WOT (WIDE OPEN THROTTLE) LOAD CONTROL VALVE
Some EGR systems feature a load control valve that closes the EGR valve when the engine requires maximum power at or near wide open throttle.
The WOT valve is installed in the vacuum line between the ported vacuum connection on the carburetor and the EGR valve. A vacuum line from the carburetor venturi vacuum tap is connected to the top part on the WOT valve and provides control for the valve. When venturi vacuum is at a predetermined level near wide open throttle, it is strong enough to overcome the calibration spring pressure and unseat the diaphragm valve, diverting EGR source vacuum to the atmosphere and causing the EGR valve to close. Normal EGR flow is resumed when there is a reduction in engine load from the wide open throttle condition.
Some EGR systems feature a load control valve that closes the EGR valve when the engine requires maximum power at or near wide open throttle.
The WOT valve is installed in the vacuum line between the ported vacuum connection on the carburetor and the EGR valve. A vacuum line from the carburetor venturi vacuum tap is connected to the top part on the WOT valve and provides control for the valve. When venturi vacuum is at a predetermined level near wide open throttle, it is strong enough to overcome the calibration spring pressure and unseat the diaphragm valve, diverting EGR source vacuum to the atmosphere and causing the EGR valve to close. Normal EGR flow is resumed when there is a reduction in engine load from the wide open throttle condition.
Laughing Gas
Joined: Apr 2013
Posts: 1,049
Likes: 65
Thanks Jim,
I guess if you're gonna hijack, go big or go home!
I've been meaning to verify the function of my vacuum advance. Could I tell if it wasn't working just from drivability? It seems to run well enough....any tests you could recommend?
I guess if you're gonna hijack, go big or go home!
I've been meaning to verify the function of my vacuum advance. Could I tell if it wasn't working just from drivability? It seems to run well enough....any tests you could recommend?
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
APC huh?
I can't make out the model year just above NON-CATALYST
What is the GVW of your RV?
What color is your vacuum restriction?
Try shifting your vacuum advance to a manifold source with the engine warm.
Notice the increased timing and RPM's?
This is to help cool the engine if stuck in traffic or similar.
(of course if you have an automatic, you have to hold the brakes!)
If driveability is good I would be fairly confident that the vacuum advance is functioning correctly.
My truck does not do well without it.
I can't make out the model year just above NON-CATALYST
What is the GVW of your RV?
What color is your vacuum restriction?
Try shifting your vacuum advance to a manifold source with the engine warm.
Notice the increased timing and RPM's?
This is to help cool the engine if stuck in traffic or similar.
(of course if you have an automatic, you have to hold the brakes!)
If driveability is good I would be fairly confident that the vacuum advance is functioning correctly.
My truck does not do well without it.
Laughing Gas
Joined: Apr 2013
Posts: 1,049
Likes: 65
I think the year on that sticker is 1986, however it's considered an '87. Here's the other sticker under the hood:
I don't know the official GVW. Is it on the door sticker? I'll have to look for that and the color of the V REST next time I get it out, but I can tell you it scales a little over 10,000 lbs fully loaded.
I don't know the official GVW. Is it on the door sticker? I'll have to look for that and the color of the V REST next time I get it out, but I can tell you it scales a little over 10,000 lbs fully loaded.
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
Over 10k is a step up from my pickup.
Plus your F53 was not sold as a complete vehicle by Ford.
That would help explain the difference between model years.
I'm really hoping to find the proper diagram for F100MANN
Plus your F53 was not sold as a complete vehicle by Ford.
That would help explain the difference between model years.
I'm really hoping to find the proper diagram for F100MANN
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
In looking back at BrnFree's (and my) EGR routing it seems that ported vacuum is routed through the VCV.
Which moves when warm to direct it to the Vacuum Delay Valve, which opens slowly, preventing a stumble.
From there to the EGR and Purge Valves.
Which moves when warm to direct it to the Vacuum Delay Valve, which opens slowly, preventing a stumble.
From there to the EGR and Purge Valves.
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Moderator
Joined: Nov 2007
Posts: 22,415
Likes: 92
From: Denver Metro Area, CO
There are similar valves/restrictors/amplifiers/check valves/doodads that perform other drivability functions, e.g. prevent backfire on deceleration, change the distributor's vacuum advance from ported to manifold vacuum when running hot, etc. Impressive what they accomplished if you ask me...
Also makes me understand how computer controls are the best things to happen to engines since the invention of the distributor but that's too far off topic.
Moderator
Joined: Jan 2001
Posts: 56,992
Likes: 2,741
From: Virginia
This is an example of how Detroit amazes me sometimes, how they accomplished what they did using only vacuum and temperature (before computers got involved).
There are similar valves/restrictors/amplifiers/check valves/doodads that perform other drivability functions, e.g. prevent backfire on deceleration, change the distributor's vacuum advance from ported to manifold vacuum when running hot, etc. Impressive what they accomplished if you ask me...
Also makes me understand how computer controls are the best things to happen to engines since the invention of the distributor but that's too far off topic.
There are similar valves/restrictors/amplifiers/check valves/doodads that perform other drivability functions, e.g. prevent backfire on deceleration, change the distributor's vacuum advance from ported to manifold vacuum when running hot, etc. Impressive what they accomplished if you ask me...
Also makes me understand how computer controls are the best things to happen to engines since the invention of the distributor but that's too far off topic.
Moderator
Joined: Nov 2007
Posts: 22,415
Likes: 92
From: Denver Metro Area, CO
I hate it. They are prone to failure, the rubber lines rot, and one slip of the wrench and you have broken off a very expensive piece of plastic if you can even buy it at all. I know we sort of needed it to get to where we are today, but what a nightmare. If I were a engine engineer, and watched my wonderful design get a bad rap out in the field and my engine keep getting ruined all the time because of some little emissions piece that keeps failing, I would not be happy.
Before my 1986 Tempo got wrecked last April, it was the most modern vehicle I had my most modern vehicle right now is a 1995 Taurus SHO - actually, two of them or three if we want to include my brother's.
Yes, 30 yo plastic is pretty fragile.....
Moderator
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From: Denver Metro Area, CO
But working on 'em sucks pretty badly, and parts are hard to find and expensive.
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Cross-Country
Joined: Jul 2013
Posts: 70
Likes: 1
I finally figured out what all was wrong. Remember, I replaced the old EGR w/a new one and my truck was running funky so I pulled the hose (& stuck a screw in it). After reading all of the posts, I reconnected the EGR, examined the vacuum hose diagram and began pulling one at a time. I pulled the one off the Air Diverter Valve (anti-backfire) and the truck ran much better. I found some additional advice on the internet about the Thermactor Emissions Control system and it advised if you are replacing the ADV to also replace the Air Check Valve on the manifold tube. So, I replaced both for ~$50 and my truck is running like a champ today. Apparently, most of my emissions system had seen better days (why it was running funky) and now nearly all of it is new, running smooth.
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