EGR valve blocked off...why?
Thread Starter
Melting Slicks
Joined: Oct 2012
Posts: 2,156
Likes: 273
From: Dunedin NZ.
EGR valve blocked off...why?
Mechanic put a blank or restrictive gasket in to block off the EGR valve, I'm not sure why but thought I would ask for opinions before I go back to him. All of the rest of the EGR system in in place plus cats O2 sensors etc.
Melting Slicks
Joined: May 2002
Posts: 2,263
Likes: 414
From: Muskogee OK
Cruise-In VI Veteran
It will effect MPG negatively, and adversely affect timing. Nothing you should feel by the seat of your pants, unless you get on it hard with the wrong fuel. Some people have had idle or low speed issues from nonfunctional or deleted EGR issues
The EGR system is very basic with no feedback to the PCM that the EGR is disconnected or non functional. Timing and base fueling is actually affected in its own tuning table depending on when the EGR is commanded on, or off. Since there's no feedback, the tuning expects it to work and changes things expecting it to be functional
I already hear the keyboard warriors pounding the keys rapidly for their rebuttal. Yes, in theory the o2 sensors keep the fueling under control, but timing is altered. All you have then is the knock sensor to adjust timing once it's no longer efficient, due to the tuning expecting less O2 in the cylinders from the EGR filling the cylinders up with inert gasses, therefore needing less fuel to make the o2's see 14.1 that they chase and different spark maps for less fuel at corresponding rpm and vacuum readings
If you get nothing else out of my reply,
If you don't do your own tuning it's best to keep the EGR functional.
If you do there's an easy work around, just set the EGR to not activate until the coolant temp is 320⁰F
Then there's no timing or fueling changes being made to piddle with and deleting the EGR physically is safer
The EGR system is very basic with no feedback to the PCM that the EGR is disconnected or non functional. Timing and base fueling is actually affected in its own tuning table depending on when the EGR is commanded on, or off. Since there's no feedback, the tuning expects it to work and changes things expecting it to be functional
I already hear the keyboard warriors pounding the keys rapidly for their rebuttal. Yes, in theory the o2 sensors keep the fueling under control, but timing is altered. All you have then is the knock sensor to adjust timing once it's no longer efficient, due to the tuning expecting less O2 in the cylinders from the EGR filling the cylinders up with inert gasses, therefore needing less fuel to make the o2's see 14.1 that they chase and different spark maps for less fuel at corresponding rpm and vacuum readings
If you get nothing else out of my reply,
If you don't do your own tuning it's best to keep the EGR functional.
If you do there's an easy work around, just set the EGR to not activate until the coolant temp is 320⁰F
Then there's no timing or fueling changes being made to piddle with and deleting the EGR physically is safer
Last edited by flannel_man; Aug 19, 2025 at 03:57 AM.
Melting Slicks
Joined: Nov 2016
Posts: 2,256
Likes: 3,084
From: So Cal
2023 C4 of the Year Finalist - Unmodified
You will also get annoying Service Engine Soon warnings because of the disabled EGR. The Code 32 diagnostic runs at highway speed with about 60 seconds of no zero-throttle. When the conditions for the Code 32 diagnostic to run exist, the test fails, and the light comes on. Annoying.
Thread Starter
Melting Slicks
Joined: Oct 2012
Posts: 2,156
Likes: 273
From: Dunedin NZ.
It will effect MPG negatively, and adversely affect timing. Nothing you should feel by the seat of your pants, unless you get on it hard with the wrong fuel. Some people have had idle or low speed issues from nonfunctional or deleted EGR issues
The EGR system is very basic with no feedback to the PCM that the EGR is disconnected or non functional. Timing and base fueling is actually affected in its own tuning table depending on when the EGR is commanded on, or off. Since there's no feedback, the tuning expects it to work and changes things expecting it to be functional
I already hear the keyboard warriors pounding the keys rapidly for their rebuttal. Yes, in theory the o2 sensors keep the fueling under control, but timing is altered. All you have then is the knock sensor to adjust timing once it's no longer efficient, due to the tuning expecting less O2 in the cylinders from the EGR filling the cylinders up with inert gasses, therefore needing less fuel to make the o2's see 14.1 that they chase and different spark maps for less fuel at corresponding rpm and vacuum readings
If you get nothing else out of my reply,
If you don't do your own tuning it's best to keep the EGR functional.
If you do there's an easy work around, just set the EGR to not activate until the coolant temp is 320⁰F
Then there's no timing or fueling changes being made to piddle with and deleting the EGR physically is safer
The EGR system is very basic with no feedback to the PCM that the EGR is disconnected or non functional. Timing and base fueling is actually affected in its own tuning table depending on when the EGR is commanded on, or off. Since there's no feedback, the tuning expects it to work and changes things expecting it to be functional
I already hear the keyboard warriors pounding the keys rapidly for their rebuttal. Yes, in theory the o2 sensors keep the fueling under control, but timing is altered. All you have then is the knock sensor to adjust timing once it's no longer efficient, due to the tuning expecting less O2 in the cylinders from the EGR filling the cylinders up with inert gasses, therefore needing less fuel to make the o2's see 14.1 that they chase and different spark maps for less fuel at corresponding rpm and vacuum readings
If you get nothing else out of my reply,
If you don't do your own tuning it's best to keep the EGR functional.
If you do there's an easy work around, just set the EGR to not activate until the coolant temp is 320⁰F
Then there's no timing or fueling changes being made to piddle with and deleting the EGR physically is safer
Thread Starter
Melting Slicks
Joined: Oct 2012
Posts: 2,156
Likes: 273
From: Dunedin NZ.
You will also get annoying Service Engine Soon warnings because of the disabled EGR. The Code 32 diagnostic runs at highway speed with about 60 seconds of no zero-throttle. When the conditions for the Code 32 diagnostic to run exist, the test fails, and the light comes on. Annoying.
