EGR Blanking Test - Diesel Engines (Mk4 Mondeo) -

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EGR Blanking Test

egr mot

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#1 Kish4511



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Posted 09 March 2021 - 08:34 PM



I am planning on blanking the EGR valve to test emissions following a MOT emissions problem.


There seems to be two options where the blanking plate might go, In the pictures i have labelled them A or B. Does anyone know the correct place for the Blanking Plate ?





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Edited by Kish4511, 09 March 2021 - 08:38 PM.

#2 Squirt


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Posted 09 March 2021 - 10:52 PM


B will be fine and easiest to blank
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#3 TheAntman


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Posted 11 March 2021 - 09:49 AM

Considering that the EGR system is intended to LOWER emissions and that your engine likely has an O2 sensor on the exhaust, I can see a couple of problems that you may encounter by blanking off the EGR.

Firstly, because your car will be measuring O2 levels in the exhaust, the PCM will be looking for pre-determined levels under EGR valve operating conditions. If the O2 levels are not what it expects, it will throw a code and put your SES light on, which, of course, is a MoT failure.

Secondly, if your emissions are already at a level which has resulted in a MoT failure, I very much doubt that blocking off the EGR will have the impact that you are looking for.

I have my EGR blanked off, but I have the 1.8 TDCI engine which does not have an O2 sensor on the exhaust - and so doesn't throw any codes, but I have also rebuilt my engine (following a cambelt failure) where I fitted brand new pistons and valves, along with a brand new inlet manifold, and the first MoT I had following the rebuild, the tester remarked that my emissions were lower than he has seen on vehicles undergoing their first MoT.

To be fair, I'm not a fan of EGR systems, as they generate a lot of soot - especially in Diesel engines, and can increase fuel consumption

#4 getsome


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Posted 11 March 2021 - 11:16 AM

EGR only lowers NOx and MOT measures opacity which will be lower without EGR...

#5 Kish4511



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Posted 11 March 2021 - 11:52 PM

Thanks Tony and Raffe. I will fully blank the EGR first and then test. I will expect the MIL will come on, but if the opacity is reduced then I will put in a plate with a small hole. I did this when I had the MK 3 Mondeo - hoping it works this time as well to stop the MIL staying on - allowing some O2 access. 


The aim here in a very big way is find out what is going on with my DPF which is recording a SOOT LOAD of 0%, this is root cause of MOT issue I suspect / guess.  This test will hopefully bring me one step closer to understanding the cause of the problem, especially if the EGR blanking leads to a drop in Opacity.


I am going to try and clean the EGR valve while I am at this task too to try and understand levels of carb build up. 

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