LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

CHK ENG light because of EGR Flow Malfunction

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Old Apr 6, 2007 | 09:00 PM
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CHK ENG light because of EGR Flow Malfunction

Noticed this today, went to autozone and they read it as an EGR valve. I have my cars rear O2's and AIR tuned out. I really dont want to blow 50$ on this egr valve since I just passed emissions a couple months ago and my cars already polluting anyways. Is there an fuel economy reduction or performance in not getting this fixed?
Old Apr 7, 2007 | 08:30 AM
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You can have it tuned out, the only thing it really does is to help minimize detonation at cruising speeds but this is debatable.

It as no effect on MPG.

Last edited by wrd1972; Apr 7, 2007 at 11:11 PM.
Old Apr 7, 2007 | 08:39 AM
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It DOES affect MPG...not a lot....maybe 1/4-1/2 MPG.Also helps control spark knock.
Old Apr 7, 2007 | 11:03 PM
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well i always run 93 octane in it, and the cars been tuned for 93 octane
Old Apr 8, 2007 | 10:18 AM
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Have you done any recent exhaust mods and then had the code pop up? When I did the long tubes, I got an EGR code related to poor flow due to what I researched to be a "backpressure" issue. Apparently, the EGR valve needs a certain amount of backpressure to operate and by putting on the long tubes, ORY, and cutout, I'm guessing I wasn't getting it. Madz28 was able to tune the PCM accordinally where I have a fully functional EGR system, but it still works around the exhaust setup.
Old Apr 16, 2007 | 01:45 PM
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Originally Posted by 2000GTP
Have you done any recent exhaust mods and then had the code pop up? When I did the long tubes, I got an EGR code related to poor flow due to what I researched to be a "backpressure" issue. Apparently, the EGR valve needs a certain amount of backpressure to operate and by putting on the long tubes, ORY, and cutout, I'm guessing I wasn't getting it. Madz28 was able to tune the PCM accordinally where I have a fully functional EGR system, but it still works around the exhaust setup.
WEll I recently opened up the cutout and had been driving with that open for a while (since it got warm out), before when the cutout was closed it didnt have this code. Although I have stock headers/ and stock ypipe w/ gutted cats leading to a magnaflow catback w/ 3" cutout before the axel. I make these 200 mile trips a lot going from college back home.

I have driven before w/ the cutout open last year and It didnt get the code. Then again this code did come after I was doing 90mph on the expressway during a 200 mile trip. Not sure exactly when the code came up but sometime near the end, as I noticed it the next time I turned my car on after the trip.

Would closing the cutout and pulling the PCM BATT fuse reset the code?
Old Apr 17, 2007 | 09:14 AM
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anyone?
Old Apr 17, 2007 | 11:21 AM
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That'll erase the code, but it probably happen again. Was it the P0400 code?
Old Apr 17, 2007 | 11:27 AM
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Originally Posted by moparman
That'll erase the code, but it probably happen again. Was it the P0400 code?
Not positive, but it prolly was, it said something about EGR Flow malfunction.
Old Apr 25, 2007 | 07:17 PM
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I have the same exact problem. Driving home from classes the other day and SES popped up. Autozone said it was a p0400 EGR MALFUNCTION.

stuck my thumb in the EGR Valve back there while idleing to rough it up a bit and it seemed to be working fine, all vacum lines looks good too. the autozone guy cleared the code for me but it always comes back in a day or 2.
i've already took off the EGR valve and checked i out and all looks good.
but it did have a sloshy sound to it liek here was water or sumthing in there....i couldn't figure that one out. time for a new EGR valve??

this is a recent issue and i've had my long tubes and cutout for over a year now.

any suggestions would be nice....
Old Apr 25, 2007 | 10:20 PM
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Originally Posted by joeSS97
It DOES affect MPG...not a lot....maybe 1/4-1/2 MPG.Also helps control spark knock.

It seems that just as mine failed i was getting more like a 2-3MPG difference. I wasnt able to make it through the week anymore, i drive about 35miles/day Monday through Sat. (sunday is autocross day it doesnt count). All city driving. My highway MPG has gone down too. I havent calculated it,but it seems that, on sunday, when i make my trip two hours away; i havent been doing too well. Its all 6th gear for an hour and thirty minutes.
Old Apr 26, 2007 | 06:51 PM
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I think its a backpressure problem, this is the first time I've been driving a lot w/ the cutout open, and I have gutted cats w/ catback. I'm gona cap it and see if it goes away once I get back home from school.
Old Apr 27, 2007 | 11:52 AM
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Originally Posted by Jazsun
I think its a backpressure problem, this is the first time I've been driving a lot w/ the cutout open, and I have gutted cats w/ catback. I'm gona cap it and see if it goes away once I get back home from school.
Thats the easiest way of finding out. Keep us updated.
Old May 15, 2007 | 08:09 PM
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Yeah, capped the cutout and after 10 miles the SES went off!
So for future reference anyone who has this problem.
Catback + Cutout + Gutted Cats on stock dual cat ypipe = EGR malfunction because of low backpressure.
Old May 16, 2007 | 08:03 AM
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Originally Posted by Jazsun
Yeah, capped the cutout and after 10 miles the SES went off!
So for future reference anyone who has this problem.
Catback + Cutout + Gutted Cats on stock dual cat ypipe = EGR malfunction because of low backpressure.
I know Madz28 was able to do a tune on my car that kept the EGR intact and functional, but also worked around my higher flowing exhaust.



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