what is the egr and evap??? what is the benifets and sideaffects of removing these things. and im assuming its gonna have to be tuned in if there removed??

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white 04 comg G gtp. wizair and pacesetters
personal best 14.6 91mph 2.1 60"
track day in a few weeks

EVAP takes the evaporated fumes from your gas tank (stored in the charcoal canister) and sucks them into the intake manifold, reusing them. Otherwise they just eventually disappear. I can't think of any reason to remove your EVAP and it can save you fuel.

EGR flows a certain amount of exhaust gas into the intake to cool combustion chamber temps. Yes, exhaust gas is hot, but the fact that it's inert gas (won't combust) it only acts as filler. The PCM can command less fuel, which is the primary reason combustion chamber temps come down. It can simultaneously advance timing taking advantage of the cooler temps giving you better mileage.

Some don't like it because the exhaust gasses can dirty you intake runners. Also, the advanced timing can cause knock if your EGR isn't up to 100%. I simply disabled mine in my PCM and I'm satisfied.

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2004 Impala LS - got some mods
NAIOA Moderator

Making you think twice before picking on Impalas

is it worth taking the egr off??

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white 04 comg G gtp. wizair and pacesetters
personal best 14.6 91mph 2.1 60"
track day in a few weeks

I don't see why you even need to take it off completely. It can be disabled in the PCM and the valve never opens. Good as removed, but if you need to enable it it just takes a few point and clicks.

Granted, even disabled it the PCM will still self test it. On decel it will open the valve a very small amount to see the MAP value rise the expected amount so it knows it still works. So, a little exhaust gas still makes it into the intake but it's hardly anything. Also, those with the L36 may want to remove it to prevent a future problem. The exhaust stack gets hot and likes to melt the plastic UIM. GM's latest design of the L36 UIM fixed the problem, but I don't know what years had it. I know mine does.

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2004 Impala LS - got some mods
NAIOA Moderator

Making you think twice before picking on Impalas

well ive heard its kinda hard to get the egr on some headers (i got pacesetters waiting to go on so idk) and i was wondering if i couldent make it work if i could just remove it with no ill side effects.

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white 04 comg G gtp. wizair and pacesetters
personal best 14.6 91mph 2.1 60"
track day in a few weeks

It won't really affect your car being removed, no. I'm planning on one day having ZZP headers and they don't even have the tube for it. You'll need to get the code removed and if you have emissions testing where they hook up to your car you might fail.

I forgot to mention that the EGR is also an emission control system (less fuel used is less emissions and the exhaust gasses limit the development of hydrocarbons).

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2004 Impala LS - got some mods
NAIOA Moderator

Making you think twice before picking on Impalas

well i dont have emisions so thats cool. i dont have a programmer tho so if i dont get it tuned out right away will the pcm still try and use the process. our pcms seem to be pretty smart tho and it seems like it would work its self out after a few days or so. i could be way off tho

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white 04 comg G gtp. wizair and pacesetters
personal best 14.6 91mph 2.1 60"
track day in a few weeks

It'll realize as soon as you start it and the EGR valve isn't plugged up. You'll also get a check engine light almost immediately.

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2004 Impala LS - got some mods
NAIOA Moderator

Making you think twice before picking on Impalas

the check engine light will be okay till i can get it tuned. i just dont want it to mess anything up trying to do something that it cant do.

on a side note. i hear that exhaust wrap is bad for headers because it holds in moisture and ruins the headers. were does the mositure come from?? can i get some water proof spray and soak down the wrap and let it dry before i wrap the headers up?? the heat would problew just burn it off anyways tho. idk????

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white 04 comg G gtp. wizair and pacesetters
personal best 14.6 91mph 2.1 60"
track day in a few weeks

Moisture comes from the air. If it gets in there it can become trapped and not evaporate fully. Headers should be coated, not wrapped.

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2004 Impala LS - got some mods
NAIOA Moderator

Making you think twice before picking on Impalas