EGR System Check
Fleet Owner
Joined: Aug 2005
Posts: 23,667
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From: Easton,Ks
Originally Posted by grena
What is the best way to verify the functionality an EGR system from top to bottom?
Vehicle: 1988 F-150 302 AOD
Vehicle: 1988 F-150 302 AOD
https://www.ford-trucks.com/forums/s...d.php?t=466068
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Junior User
Joined: Feb 2006
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Are these all the parts of the EGR system?
EGR valve
" " Position Sensor
EGR Vacuum Regulator
Vacuum Lines
Wiring to Sensor and Regulator
I can check for voltages and continuety (where applicable) @ the sensor and regulator...but what I am not sure about is checking the vacuum aspect of the system.
How much vacuum should going to the module and how much vacuum going to the EGR valve from the module @ idle, 1200 rpm, 2000 rpm etc.??
EGR valve
" " Position Sensor
EGR Vacuum Regulator
Vacuum Lines
Wiring to Sensor and Regulator
I can check for voltages and continuety (where applicable) @ the sensor and regulator...but what I am not sure about is checking the vacuum aspect of the system.
How much vacuum should going to the module and how much vacuum going to the EGR valve from the module @ idle, 1200 rpm, 2000 rpm etc.??
Fleet Owner
Joined: Aug 2005
Posts: 23,667
Likes: 301
From: Easton,Ks
Originally Posted by grena
Are these all the parts of the EGR system?
EGR valve
" " Position Sensor
EGR Vacuum Regulator
Vacuum Lines
Wiring to Sensor and Regulator
I can check for voltages and continuety (where applicable) @ the sensor and regulator...but what I am not sure about is checking the vacuum aspect of the system.
How much vacuum should going to the module and how much vacuum going to the EGR valve from the module @ idle, 1200 rpm, 2000 rpm etc.??
EGR valve
" " Position Sensor
EGR Vacuum Regulator
Vacuum Lines
Wiring to Sensor and Regulator
I can check for voltages and continuety (where applicable) @ the sensor and regulator...but what I am not sure about is checking the vacuum aspect of the system.
How much vacuum should going to the module and how much vacuum going to the EGR valve from the module @ idle, 1200 rpm, 2000 rpm etc.??
The Vacuum should be zero at idle, maximum at cruse and zero at full (WOT) power.
In other words zero at idle for a smooth idle.
Zero at WOT to give maximum power. (Note engine vacuum is low at this point also)
Maximum vacuum as you drive down the road and the engine can handle the EGR.
Last edited by subford; Mar 1, 2006 at 09:07 AM.
Junior User
Joined: Dec 2002
Posts: 71
Likes: 0
From: Deer Park USA
One thing that helps is a vacuum pump/gauge tester. I got one for about $25 bucks and it is neat because you can apply vacuum directly to the EGR valve at idle and hear the effect on the idle as you apply it and hear the idle straighten up once you release the vacuum. If that works then you have a reasonable indicator that the EGR valve itself is working. If it doesn't then either the valve seems to be stuck shut or passages are completely plugged.
If the valve looks okay turn the tester around and connect it to the hose that feeds the EGR valve. As said before, at idle it should be at or near zero. As you smoothly increase the RPMs the vacuum should climb to 5" - 10" maybe more. But note that the reading will take a dive to zero if you twitch on the throttle. Any throttle change apparently causes the EGR to be slapped shut. If you dont get that then you can back up to the vacuum modulator and see if it has good vacuum coming in. If it does, the modulator may be hosey (it is driven by the PCM and is duty cycle modulated.....the timing of the signal controls the amount of vacuum that gets gated out). If not you gotta fix that first.
Bear in mind....all of this is for my '87 4.9L.
If the valve looks okay turn the tester around and connect it to the hose that feeds the EGR valve. As said before, at idle it should be at or near zero. As you smoothly increase the RPMs the vacuum should climb to 5" - 10" maybe more. But note that the reading will take a dive to zero if you twitch on the throttle. Any throttle change apparently causes the EGR to be slapped shut. If you dont get that then you can back up to the vacuum modulator and see if it has good vacuum coming in. If it does, the modulator may be hosey (it is driven by the PCM and is duty cycle modulated.....the timing of the signal controls the amount of vacuum that gets gated out). If not you gotta fix that first.
Bear in mind....all of this is for my '87 4.9L.
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bigmacmonday
1987 - 1996 F150 & Larger F-Series Trucks
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