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EGR question

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  #1  
Old 07-10-2018, 05:55 PM
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EGR question

With no vacuum applied should any air move through EGR valve ? What difference would it make if you used a block off plate on a 2000 f150 5.4?
 
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Old 07-10-2018, 06:12 PM
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No. If you block it off, you will have a CEL and you will lose some gas mileage.
 
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  #3  
Old 07-10-2018, 07:21 PM
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There are no benefits on modern engines by blocking off EGR.
EGR is exhaust gas recirculation.
Not clean airflow

There are two things to know about this.

1. The computer tests the EGR operation everytime the motor is started.
If there is a failure a code is set and CEL comes on. This inhibits the operation.

2. The EGR functions at preset points while driving. This is separate from the tests that are done to make sure the system functions properly.
.
Normally the function is transparent while driving with no loss of power.
This action reduces combustion temperatures in the cylinders to reduce oxide emissions as mandated by the federal government..
When it is called to open, ignition timing is advanced, fuel injection is reduced. This results in a small increase in fuel mileage.
For no advantage, advise not to disable this function.
 
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Old 07-10-2018, 09:07 PM
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thanks for the quick answer guys been tracing a running rich problem and although the EGR valve looks new (just bought the truck ) with no vac applied you can blow through the valve. when looking for a new valve I noticed some are just blocking it off so I thought I would get some more opinions.
 
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Old 07-10-2018, 09:37 PM
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The EGR is normally closed at all times but when requested to open either during the test or when on the road under the proper conditions.
When you say you can blow through it, how does that come about?

The EGR valve must have vacuum applied and ports behind it open for that to happen unless the EGR valve is faulty. It has a spring loaded rubber diaphragm that opens the port when vacuum is applied.
This system won't cause a rich condition under any circumstances.
IF your sure you have a rich condition, it should be supported by codes.
A Scanner looking at the long term fuel trim tables will tell you what you have, rich, lean or in normal limits.
Do not try to guess what's going on until you have made some diagnostics and know what your chasing.
Good luck.
 
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Old 07-10-2018, 11:05 PM
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BLUEGRASS
after removing the EGR valve I literally blew through the fitting for the exhaust tube and could feel and hear the air whistle through

using a scanner get 175 code and Ltft bank 1 -3to12% Bank 2 -18 to -25+%
All new injectors
new coils
new plugs
fuel pressure 34
holds fuel pressure for more than 15 minutes with ignition off
vacuum 18 steady
4 new o2 sensors
all new exhaust
all new cats

also cant complete EGR test thus removal and old school test
 
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Old 07-11-2018, 01:11 AM
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If you can pass air through the EGR valve in your hand it is faulty. Diaphragm is open, spring broken or being held open for some reason. This should cause a Code 402 an excessive flow test failure.
If you have an open or leaky EGR valve in place, it will pass Exhaust gas and cause rough running. Exhaust does not burn the second time therefore cannot cause excessive richness by causing a shift in the fuel table that would go lean not rich..
.
Code 175 is bank 2 rich. That means the long term trim for bank 2 has a 'negative shift' more than 25% to the Lean side of the table trying to counter the rich condition cause by shutting down the fuel injection pulses widths for that bank..
Faulty fuel injector bank 2 or fuel regulator diaphragm has ruptured to allow raw gas to enter the intake.
Excess fuel is the only way an over rich condition can occur. Not excessive air.
An EGR system fault cannot do this.
An EGR system fault is a second trouble to work out.
Looks like you have two issues at the same time causing confusion.
You have to be careful how you interpret the codes.
The program has to also interpret the hardware failure and often has to do it in reverse for description. You have to know this is the way it's done
For rich and lean conditions the OX Sensors become the main indicator of the results detected in the exhaust for what happened upstream in the engine THEN causes a shift in fuel tables.
Good luck.
.
 

Last edited by Bluegrass; 07-11-2018 at 01:19 AM.
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Old 07-11-2018, 12:17 PM
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BLUEGRASS
Just for clarity Im not claiming the EGR valve for the rich code just that I found it while tracing the rich code.I removed the EGR valve to get better access to fuel rail and used the old school method of blowing through it with no vac and found it faulty . the strange part is the truck idles smooth even with AC on purrs like a kitten never threw a code for EGR except couldnt complete EGR test and there is no doubt in my mind the valve is bad. The trucks problem now is loss of power on a hard pull like a hill.Even on a hill the LTFT is in the negative numbers
 
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  #9  
Old 07-11-2018, 12:39 PM
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The way your reporting things is confusing.
It's difficult to tell what your doing.
I can only reply based on what you say. If I miss understand, the reply becomes meaningless.
.
Start over again and tell what the drivability issue is 'now' without all the extras.
I explained how the EGR works.
If you see an issue with it, it's another problem. If there is no fault code when put back together, then it's good. Simple as that. The computer test is never wrong on this system.
.
I know it may be difficult to understand the rich code as explained but it can't be said any simpler.
Your dealing with a computer interpretation on that side, not the engine side that caused it.
The computer generates the code related to the outside cause.
It is done that way because the same computer is used on many different engines that are equipped with different hardware systems it has to respond to.
There are nearly 2000 possible codes stores in the computer program.
 
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  #10  
Old 07-12-2018, 08:07 PM
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BLUEGRASS
what readings would you get on a live data scanner if theres a bent fuel rail causing the motor to suck air at the base of a fuel injector?
 
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  #11  
Old 07-12-2018, 09:48 PM
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I don't think you could see anything on a Scanner that 'points' to what you are asking about.
I can tell you with near certainty that you should see a pretty good fuel leak because the rail cap is on the pressure side of the injector (top).
The bottom of the injector is inside the manifold.
Both top and bottom has O ring seals.
Top to hold the rail pressure, bottom for a vacuum seal.
The injectors are under about 35 psi +/- at that point.
If the leak is big enough in volume at the leak point the pressure in the 'rail' will go down some amount.
It's really not a question of sucking air being more important than the gas leak.
Depending on the specific circumstances it might be detected as a shift in fuel tables but unless you looked first, then done the repair and looked again you might not be able to tell.
 
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