# Can I block off my EGR valve?



## mscar111 (Mar 15, 2018)

If I block off my EGR valve, will the car run ok without it? or since the car is designed with it, is it going to confuse the computer and make my car run poorly?


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## smj999smj (Jan 1, 2006)

Yes, but keep in mind that the EGR valve does have a purpose in that it is used to control combustion chamber temperatures which helps prevent detonation and reduce NOx emissions. Will it run okay?: yes, but you will have the check engine light coming "on" because the ECM will see that the EGR system is not working.


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## mscar111 (Mar 15, 2018)

smj999smj said:


> Yes, but keep in mind that the EGR valve does have a purpose in that it is used to control combustion chamber temperatures which helps prevent detonation and reduce NOx emissions. Will it run okay?: yes, but you will have the check engine light coming "on" because the ECM will see that the EGR system is not working.


Correct me if I'm wrong, but doesn't it regulate the combustion chamber temps by replacing some of the cold air by recirculating nasty hot exhaust back into the chamber, thus causing the explosion inside the chamber to be smaller and at lower temperatures? So for example (I don't know the amounts) but lets say there is 20% gas, and 80% cold air inside the chamber, and with the EGR valve working, it becomes 20% gas, 70% cold air, and 10% hot exhaust. From my understanding, exhaust is not flammable or at least it's not as good as adding more air and gas to the mixture, and by taking up room in the chamber with something that isn't flammable or not as flammable, your essentially making your chamber smaller by taking up room, and also creating a smaller and cooler explosion that will cause your piston to slow down on when going down.

To me it seems like all your doing is decreasing RPM, putting more strain on your engine, gunking it up with nasty exhaust, and only delaying the exhaust from exiting the engine because it's not going to disappear.

My only concern is that I'll have to remap my ECM because the car will have to account for it not working, or maybe the car has already put itself into some type of safe mode because now the timing and force of the pistons aren't matching up to what it thinks it should be doing.


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## smj999smj (Jan 1, 2006)

Well, first, keep in mind modern EGR systems are a lot better than they were when they came out in the '60s. Inert exhaust gas is only added under certain condition, essentially during light acceleration and cruising conditions but not during wide open throttle, at idle or when the engine is still cold. Also, when it is uses, only a very minute amount of inert exhaust gas enters the combustion chamber and no where near 10% of the mixture. 
The big issue is combustion chamber temperatures; when the reach around 2500 degrees F. and above, which does occur, oxides of nitrogen are created (which are bad for the environment). Also, temperatures above 2500 degree F., the air/fuel mixture can spontaneously combust (much like in a diesel engine) and can cause pre-ignition, valve clatter and subsequent engine damage. Prolonged exposure to pre-ignition detonation can lead to the pitting of piston tops and eventual burn-through. So, one can see why a properly functioning, modern EGR system is a good thing! Of course, there is a compromise. As you pointed out, exhaust gas, even in very small amounts, does contain carbon that can clog those EGR passages and cause varnishing of the throttle body, so a little additional maintenance is required every so often. 
If you do go ahead and block off the EGR, you shouldn't have to do any ECM re-mapping as far as drivability, but the ECM will still see the system not working and trigger the EGR trouble code(s) and turn on the CEL.


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