ggoat!!!

Hi there...

I will be changing my intake to an LS6 soon and won't be tuning the car for quite a while, so in the meantime to prevent any codes I am thinking of disconnecting the EGR pipes leading to and from the valve but leaving the actual valve intact and electronically hooked up so that the computer "thinks" it's there.

This SHOULD prevent any codes, since the computer won't know that the valve isn't actually pumping any exhaust gases since there will be no EGR plumbing going into or out of the engine. However...

I'm not sure how the engine controls air/fuel ratio regarding exhaust gas content or how it "knows" to compensate for the exhaust gas that would normally be introduced to the intake via the EGR valve. Does the MAP sensor actually monitor in some way the presence of EGR gasses, or does it work like a "regular" MAP sensor and only adjust for simple pressures? How COULD the engine actually know if there are specifically exhaust gasses in the intake?

I see no way for the computer to "know" that I have stopped the EGR gasses from being reintroduced to the engine's intake...but again, I'm not that up on the internal computer workings of the LS1. So, it may very well "know" but I don't know how...and haven't read anything here from anyone that explains such a scenario. BUT...does anyone know FOR SURE regarding this, without mere speculation? Will the computer KNOW that the exhaust gasses are "missing" and somehow try to compensate or throw a code? Anyone know FOR SURE?


Thanks again!
Jeff

A-Dub

iTrader: (6)

Im not positive, but I believe the computer uses the MAP sensor reading as a reference to check for proper EGR opening and closing. When you open the EGR valve, there will be a change in manifold pressure. Im guessing you will still get a code.

tylerdj

iTrader: (31)

It won't read correctly and will set off an SES light.

tylerdj

iTrader: (31)

Just curious, are you concerned about the light due to inspection reasons or something else?

Mike94ZLT1

iTrader: (3)

No lights, I did this myself until I got a tune deleting the EGR on my 99 SS. I removed all the tubes and left the thing plugged in, and it was fine.

ggoat!!!

Thanks Silver...but I'm trying to find out for sure.


Tylerdj..."what" won't read correctly? Are you just guessing, or did you actually try what I'm wanting to do? I don't want a CEL...makes me think I'm driving an '82 Escort with a plugged cat.


Mike...thanks for the firsthand info! So, no detrimental effects of any kind doing removing the EGR like this?



Thanks,
Jeff

Ferocity02

iTrader: (60)

Technically it should throw a code. There are other sensors that will know something is up. But, it may take awhile for the computer to realize something is wrong. For example, I accidently left one of my AIR hoses disconnected from the driver's side header and the computer took three weeks to figure out something was wrong and throw a code.

MrDude_1

iTrader: (4)

it will take a sustaned cruise with little throttle movement before it will throw a code.. but yes, it will eventually notice its not working.


btw, even my 91 camaro could figure out if the EGR worked...

ggoat!!!

Do you guys know for sure or are you just speculating?


"There are other sensors that will know something is up." Any specifics?

"It will eventually notice its not working." What is "it"??? And, how will "it" know?

MrDude_1

iTrader: (4)

i know for sure that it will.

the way it works... well there are two ways.

the MAP sensor, and the O2 sensor.

the MAP sensor method makes it look for a change when it opens the EGR valve.

the o2 sensor expect to detect less oxygen because the intake charge is deluted.


now, it doesnt throw the code right away because it averages the changes over time, to decide if its was just an odd reading, or if it was really an error code.. but once its thrown, its an emissions code, and it stays litup there until you clear it with a scanner.


on my 91, the only time it could detect is part throttle highway cruising, because thats the only time the MAP signal is stable enough for it to test... on your car, it doesnt take as long because the computer is faster and the test has been refined alot. lol

ggoat!!!

Well, that makes sense...but it doesn't explain how so many people here post on here that there is no performance detriment with disconnecting the EGR without clearing the codes. If the codes were thrown, something would have to suffer.

tylerdj

iTrader: (31)

Why is that? It only shows the SES light in order to alert you that there is something wrong with the emissions system.

ggoat!!!

Because the computer would try to adjust air/fuel ratio in order to try to get it to comply with it's pre-set desired target range according to data transmitted by the O2 sensors.

staringback05

iTrader: (8)

with any code the pcm can and sometimes will throw a car into a "safe mode"...did this when i removed the AIR unit on my car....ran SLIGHTLY richer....just because the car is looking out for itself in an unknown time

MrDude_1

iTrader: (4)

with the code thrown, the car never switches to the EGR tables, and behaves just like the EGR is off.

what suffers is...... nothing, because the computer behaves the same as when the EGR is not in use.... EGR is not required for the car to operate safely.


the O2 sensors on the otherhand, are important to the safe operation of the motor... from a warranty and liability standpoint of GM.... if THEY throw a code, the car doesnt know if its running lean and hurting itself.. so it goes max rich when the code is thrown... causing a loss in performance.




remember, all codes arnt created equal.... theres also a code thrown if your gas cap isnt on tight... but theres no reason for that code to modify your engine operation..

dummer

You won't throw an SES right away, but it will before long. I tried exactly this same thing and so i know for sure. I forget DTC it throws, but it equates to " EGR flow insufficient".
But I didn't notices the car running any different. It should be fine if you are only gonna leave it that way for a little while. I left my EGR disconnected for a couple weeks, before I got tuning software and disabled EGR and AIR....