P0400 EGR flow Code - LS1LT1 Forum : LT1, LS1, Camaro, Firebird, Trans Am, Engine Tech Forums

Captainofiron · 04-19-2010, 08:19 PM

Well I have been driving around with this stupid code flashing on and off regularly for about a year

Anyways, I replaced the EGR solenoid because when I checked it, it seemed like it was broken and something inside was broken, it sounded like an empty can of spray paint.

The code went away for a week then POW

So I checked and one of the vacuum lines feeding the valve and the solenoid had a little crack

so I patched it by fully breaking the line and putting superglue on the 2 pieces and putting a correctly sized hose over the plastic line

So what else would be causing this code???

I have FLP Longtubes, with a pair of cutouts, but I dont think the cutouts or an exhaust leak could cause this code right?

I dont think its the MAP sensor either

It always throws the code when the engine is at a lower speed (~45-65mph and ~1500-2000rpm)
which makes me think its the actual operation of the EGR causing the code

If anybody could help I would really appreciate it

oh and getting rid of the EGR is not an option, got to get the sniffer for a sticker

Thanks guys

Captainofiron · 04-20-2010, 03:18 PM

nobody?

Shoebox help, haha

chrys95 · 04-20-2010, 03:21 PM

you have to pass the sniffer even though the car is OBD2, (if its the 97 in your sig)? and it passes the sniffer with longtubes?

Captainofiron · 04-20-2010, 04:21 PM

Quote:

Originally Posted by chrys95

you have to pass the sniffer even though the car is OBD2, (if its the 97 in your sig)? and it passes the sniffer with longtubes?

they are the emission compliant FLP long tubes

2fast4u88 · 04-20-2010, 05:04 PM

Well it could only be a few things. Vacuum, the solenoid or egr. Did you remove the egr and clean it or see it it even holds vacuum?

Captainofiron · 04-21-2010, 08:31 AM

Well I played with it a little last night

Yes I replaced the EGR, so the EGR and controlling solenoid are brand new

I checked the vacuum at the port and its good, but it was still really hot after sitting for a few hours, so I couldnt get the rear hoses off, and my main concern was pulling off my messed up tint

probably today I am going to go to the parts store and get 2 new fresh vacuum lines and run them to the solenoid and the egr and see if it works

it always makes me laugh the random advice the workers at autozone give you when the read your codes

Seriously...
this last time they said that my computer couldnt connect to their OBD2 scanner so I had to use the dealership, and I said, uh the key needs to be on.. then it magically worked, lol
then after it pulls the code P0400 the kid says, your EGR is bad, you need to replace it, and I said nope its a flow code
then i saw can you clear the codes, and he said no I cant it will cause an imbalance in your car and damage your engine, and I said whatever its not a warp drive and he looked at me with a stupid look on his face and his mouth open

Captainofiron · 04-22-2010, 07:46 AM

So yesterday, I checked the vacuum at the ports, and its not plugged, then I checked the lines, and they arent leaking, and I checked the EGR by moving it with my fingers, and its going in and out freely

so now Im moving on to the EGR pipe between the header and the intake

im really leery of replacing the MAF sensor, but if I dont find any leaks on the EGR pipe I dont know where else I will look

would an exhaust leak on the headers or a blown header gasket cause this code?

JSK333 · 04-23-2010, 08:53 PM

I have seen a high-flow exhaust (cat and muffler) cause this on my '90 Cadillac, but don't think I've ever heard of it happening on an F-Body.

97Trans-AM · 04-23-2010, 10:25 PM

Check you MAP, voltage should respond instantly when you snap the throttle. If it is okay, check your egr ports in your intake. This code is set when the pressure change (measured by the MAP) in the intake manifold is not within the correct range expected by the PCM.

Don't look for leaks in your EGR, look for it plugging up with carbon.

Captainofiron · 04-26-2010, 08:31 AM

Quote:

Originally Posted by 97Trans-AM

Check you MAP, voltage should respond instantly when you snap the throttle. If it is okay, check your egr ports in your intake. This code is set when the pressure change (measured by the MAP) in the intake manifold is not within the correct range expected by the PCM.

Don't look for leaks in your EGR, look for it plugging up with carbon.

what range should I be looking for when I check the MAP

I guess Im gonna have to pull off the EGR pipe from the header to the intake and spray it out with intake cleaner.
I called around looking for the gasket for this part, anybody know the part numbers?

BUTCHERZ28 · 04-26-2010, 08:51 AM

Quote:

Originally Posted by Captainofiron

what range should I be looking for when I check the MAP

I guess Im gonna have to pull off the EGR pipe from the header to the intake and spray it out with intake cleaner.
I called around looking for the gasket for this part, anybody know the part numbers?

to see if the pipe is clogged, push on the diaphram of the egr valve with your finger while the car is idling. If the idle drops or even stalls out when you push on the diaphram, the egr passages are not clogged.
there are three types of egr valves i think, and i know at least one of them use back pressure in part to operate. My car threw an egr code once when i drove it with just the y pipe on lol. Stopped throwing the code when i put my exhaust back on.

97Trans-AM · 04-26-2010, 09:13 AM

Somehow I missed that you had long tubes. Butcher is right, there are three types of egr on your car. If you have a negative back pressure egr then your longtubes are to blame. Did you engine light start coming on around the same time you put the headers on?

As far as your MAP goes just look for a sudden change in voltage on the signal wire when you snap the throttle, we are looking for response to the sudden change in vacuum not a certain range of voltage.

Captainofiron · 04-26-2010, 11:25 AM

Quote:

Originally Posted by 97Trans-AM

Somehow I missed that you had long tubes. Butcher is right, there are three types of egr on your car. If you have a negative back pressure egr then your longtubes are to blame. Did you engine light start coming on around the same time you put the headers on?

As far as your MAP goes just look for a sudden change in voltage on the signal wire when you snap the throttle, we are looking for response to the sudden change in vacuum not a certain range of voltage.

no the longtubes didnt cause it.
I had them on for maybe 2 years before I started getting these codes. In the past the only time I would get EGR codes thrown was if I ran open headers (via cutouts)

What I did notice is that I started getting it after I moved from sea level back to far west Texas (~4000ft) and the roads are alot more rough here, which made me think it was an electronic problem or something working loose with the vibrations

I still have the old EGR valve I think, I am going to check the part number and see which it is, but I do believe it is a negative backpressure one.

97Trans-AM · 04-26-2010, 11:42 AM

The altitude might be the cause of your problem. Have you tried a hard reset of your PCM after you moved? The readings on your MAP will be different because of the atmospheric pressure change and might be the issue if you haven't reset the PCM.

Captainofiron · 04-26-2010, 02:38 PM

Quote:

Originally Posted by 97Trans-AM

The altitude might be the cause of your problem. Have you tried a hard reset of your PCM after you moved? The readings on your MAP will be different because of the atmospheric pressure change and might be the issue if you haven't reset the PCM.

How exactly would one do a hard reset?

I was living here maybe for about 1-2 months when the trouble code started popping