5.4 egr block
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
It can be done mechanically but you won't gain anything for normal road use.
Just removing the vacuum hose will do the same thing not allowing it to open.
It will set a code for a 401 failure when the PCM does it's test and it fails.
When the code is present the EGR function is suspended.
This will have some effect on fuel milage.
Normally the EGR function is transparent to drivabilty unless there is a fault.
Only time EGR functions is in OD at low throttle cruise when little power is called for otherwise at about 1/2 throttle or greater it closes up.
Good luck.
Just removing the vacuum hose will do the same thing not allowing it to open.
It will set a code for a 401 failure when the PCM does it's test and it fails.
When the code is present the EGR function is suspended.
This will have some effect on fuel milage.
Normally the EGR function is transparent to drivabilty unless there is a fault.
Only time EGR functions is in OD at low throttle cruise when little power is called for otherwise at about 1/2 throttle or greater it closes up.
Good luck.
Senior User
Joined: Mar 2013
Posts: 114
Likes: 0
i was wondering about this as well, I'm currently replacing the drivers side manifold in my '98 250 5.4 4X4 and was considering "capping" the manifold until i can afford the new egr tube so i can at least drive it, I was concerned weather it would make it run rough and make the gm not worth driving it, i'm estimating that I'm about 11-12 mpg for overall avg.
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
As long as the EGR never opens to admit outside air with a missing tube it won't cause any drivabiliy issue.
But some emissions rise and less fuel mileage is the result.
The system will howerver fail diagnostics and set a code and CEL.
.
EGR:
Is short for exhaust gas recirculation.
The intent is to allow a small amount of exhaust gas back into the intake.
The purpose is to 'cool' combustion in the cylinders to a point that Nox emmissions is reduced in the final output from the tail pipe.
The Cats don't process Nox to any degree.
EGR is called to open during the drive cycle with the most, time namely in OD at light throttle where the motor spends the greatest amount to time..
The whole process is designed to be transparent to the driver as far as drivability.
Good luck.
But some emissions rise and less fuel mileage is the result.
The system will howerver fail diagnostics and set a code and CEL.
.
EGR:
Is short for exhaust gas recirculation.
The intent is to allow a small amount of exhaust gas back into the intake.
The purpose is to 'cool' combustion in the cylinders to a point that Nox emmissions is reduced in the final output from the tail pipe.
The Cats don't process Nox to any degree.
EGR is called to open during the drive cycle with the most, time namely in OD at light throttle where the motor spends the greatest amount to time..
The whole process is designed to be transparent to the driver as far as drivability.
Good luck.
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
As Paul Harvey would have said 'and now for the rest of the story'.
When the EGR is called to operate, fuel injection is cut back saving fuel and ignition timing is advanced.
With exhaust gas leaning out the air to fuel ratio at low throttle openings the motor cannot use the normal fuel amount delivered because exhaust gas does not burn the second time and there is no room for any more air and fuel in the intake stream flow.
With this condition the combustion flame travel gets a lot faster because there are less molecules to combust making the need to introduce spark earlier in the cycle before top center so maximum cylinder pressure occurrs at about the same piston travel point after top center it normally would .
Some people get confused about the lean condition being a lack of fuel or to much air. This is a special case where it's generated a different way.
When this is all corrdinated by program design it becomes transparent to normal drivability.
As soon and you call for power, the EGR is closed up and it all returns back to normal so the engine can make it's normal power.
It knows to do all this mainly by the position of the TPS and the VSS indicated speed, sensors.
"Ain't computers wonnerful"?
Good luck.
When the EGR is called to operate, fuel injection is cut back saving fuel and ignition timing is advanced.
With exhaust gas leaning out the air to fuel ratio at low throttle openings the motor cannot use the normal fuel amount delivered because exhaust gas does not burn the second time and there is no room for any more air and fuel in the intake stream flow.
With this condition the combustion flame travel gets a lot faster because there are less molecules to combust making the need to introduce spark earlier in the cycle before top center so maximum cylinder pressure occurrs at about the same piston travel point after top center it normally would .
Some people get confused about the lean condition being a lack of fuel or to much air. This is a special case where it's generated a different way.
When this is all corrdinated by program design it becomes transparent to normal drivability.
As soon and you call for power, the EGR is closed up and it all returns back to normal so the engine can make it's normal power.
It knows to do all this mainly by the position of the TPS and the VSS indicated speed, sensors.
"Ain't computers wonnerful"?
Good luck.
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