urbanhunter44

iTrader: (1)

I popped an SES light this morning. Pulled the code at work and found P0400 EGR Flow Malfunction.

I know my EGR is a backpressure operated EGR, so is it possible that with my now incredible lack of backpressure (LTs, no cats, magnaflow) it's not operating properly? Everything is correctly hooked up and worked fine before the swap.

JL8Jeff

iTrader: (14)

I didn't get that code after my LT swap with no cats. I doubt the free flowing exhaust is causing it. Try resetting the computer and see if it comes back. The code should indicate too much flow or too little, can you tell which it really is?

urbanhunter44

iTrader: (1)

All it indicates is a flow malfunction. I looked it up on the computer but that didn't tell me much more. I'v reset the computer and it came back.

RichardZ SS

Your po400 code IS due to lack of exhaust backpressure. I know because Ive got it too right now. It seems that this is only a problem on the 96 and 97 model cars, just our luck huh? Yesterday I deleted the cats and installed a Loudmouth exhaust system and thats the cause of mine. My biggest question right now, and one that I cant seem to find an answer to, is will it hurt performance or the engine to just run it like it is with the SES light on. I did a search on another forum and came up with a lot of good info, including this link giving instructions on how to fool the computer into thinking its working when its not. http://web.camaross.com/forums/showt...+monitor+ready I hope this helps you some, I know how frustrating it is to not be able to fix something. If I cant get a for sure answer soon, I guess I will try the trick in that link. I dang sure aint planning on putting the cats back on! This thing runs like a scalded dog now!

ZFan88

iTrader: (4)

How do you like the sound of that setup? I'm going with the exact same one soon..

RichardZ SS

Well to tell ya the truth, its too damn loud! Im not one of those that minds drawing attention either, but this thing is so loud you cant even TALK to anyone else in the car while driving! Im gonna be replacing the LM1 "shotgun resonator" asap with the LMII race muffler and see how much that quiets her down. If that doesnt work, Ive got a set of corvette resonators that go right at the rear exit of the car, the tips actually go on the resonators, that Im gonna try. Ive got this exact setup minus the !cats delete on our 2000 SS and it sounds SWEET!!! I guess deleting the cats and the LM1 on an LT1 is just TOO MUCH.

Captainofiron

iTrader: (1)

I would get that code only when I run with open headers, my guess is you maybe have a leak or the EGR pipe isnt connected properly to teh LTs

JL8Jeff

iTrader: (14)

I have the Pacesetter longtubes on my 96 SS and I never got the EGR code and I wasn't running cats for the first month. I'm running dual 3" cats now and still no EGR code. I'm guessing your gasket is blocking part of the flow.

RichardZ SS

Its no guess on what caused mine. I never touched the manifolds, all egr pipes and such are still EXACTLY like they were before the exhaust work. po400 is EGR malfunction: flow restricted. That sounds bassakwards, but the EGR works off of BACKPRESSURE. If it was a blockage there would be PLENTY of backpressure in the system.

A-man930

iTrader: (2)

Back from the dead... I've got the same code on my formy, and it only has a catback. Is the method in the link above reccomended if you have to pass emissions testing?

Bowtie Boy

Yeah I recently got this code too, have a LM catback, and ive been running fine for months and it just pops up. Would a mail order tune get this code out if I chose to delete egr code. I am getting a tune from pcm after headers are installed.

Revelation Z28

iTrader: (10)

this is only with the 96/97's? because when i ran open LTs i didnt get anything. i did have to crimp the EGR tube ALOT to get it to go into the hole in the primary. so i think that gave me backpressure for it. im running LTs no cat.

A-man930

iTrader: (2)

I was wondering the same thing. I am getting a madtuner tune, and I was wondering if I should use the "disable EGR function" or not. Would that take care of everything?

Revelation Z28

iTrader: (10)

yea, then youll have to get some block off plates to get rid of the EGR system.

97LT1

iTrader: (3)

The whole deal with OBD2 is that madtuner can turn off the EGR function, but it will leave a NOT READY @ the emissions testing site. 96- i think 00 are allowed 2 not ready flags to be raised when emissions testing without failing you.

So.....that means choose your things to turn off in your computer wisely.


I personally would save them for something else.

I am not sure how tuners get around raising the flags if there is any route to do that. From what i have stated , is all I know about the testing process. It would be interesting to know if there is a way around actually turning off these things via tuning. Any tuners are welcome to chime in on OBD2.

A-man930

iTrader: (2)

I think I'll just leave it on then, I can always delete it later.

smb72

I too have had this problem with PO400 on my 97 Z28 after I installed LT's. I did my searches on here and found the same info as any of you. I figured that I would try a couple things and see where it would go. First thing I did was go out and get a new EGR gasket and some carb cleaner and clean the old valve out. This is easy to do with only having to remove two nuts. After I cleaned the valve and re-installed it, I then went to the EGR tube that goes from the header to the intake and modified the bend thats in the tube. I did this in hoping to cause some backpressure. Cleared out the code to see if it was fixed. I took the car to work today and no more check engine light on. It would come on at around 15 miles. Well I put on 40+ and no light as of now. I guess all it needed was a little backpressure for it to work right.