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EGR Problem p0400 and p0403

337 Views 13 Replies 6 Participants Last post by  95wagon, 
iamGAUD
I have a 96 impala with around 140k miles on it and recently on cold start it starts bogging bad even after going into 2nd. I pulled up the codes and got p0400 and p0403. I have been running the car with the EGR lines plugged up including all the vacuum lines connected to it, basically an EGR delete without taking out the EGR, with a plug set from AutoZone. I have done that about 10k miles ago and just recently started to get drivability issues and the codes. Should I just buy the EGR delete plate and install it and not worry about the code or should I also reprogram the pcm. The car is over 26 years old so emissions should not be a problem when doing the inspection but I am not sure if without the reprogramming my bogging will go away.
Other posts said that with a modded engine the EGR is not needed but all I have done to it was the 1.6 rocker arms, lifters, and springs not sure if that counts since everyone is saying only a cam would compensate with recirculating gasses.
Im leaning towards just buying the back plate and leaving the check engine light on, but im open on what i should be doing.
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M
Seems better to diagnose the code problem(s) to find out what's going on. Pretty much four choices: bad solenoid, bad EGR valve, cracked wiring/plug at the solenoid, and/or leaking vacuum lines. See DTC section of shop manual.
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B
Deleting EGR requires PCM to tune it out

A functioning EGR system has no performance loss but will cause issues if its not fixed

so you have 2 choices, fix it or tune it out and remove it entirely using a block off plate.

IDK about what emission inspection you have...many states do require emission equipment be left on car regardless of it needing emission testing.
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iamGAUD
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MWP said:
Seems better to diagnose the code problem(s) to find out what's going on. Pretty much four choices: bad solenoid, bad EGR valve, cracked wiring/plug at the solenoid, and/or leaking vacuum lines. See DTC section of shop manual.
Click to expand...
Which solenoid are you referring too? I have disconnected pretty much anything that goes to the EGR and plugged it up, I will attach a picture on how I have it set up. It could be that one of them slipped off or cracked open so im going to check on that. I did notice my throttle body elbow has a crack I have a picture attached, that might also cause the issue.

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iamGAUD
BALLSS said:
Deleting EGR requires PCM to tune it out

A functioning EGR system has no performance loss but will cause issues if its not fixed

so you have 2 choices, fix it or tune it out and remove it entirely using a block off plate.

IDK about what emission inspection you have...many states do require emission equipment be left on car regardless of it needing emission testing.
Click to expand...
What will happen if i just put the block off plate on there without tuning it out from the car? Will it just have poor fuel mileage or something else will happen?
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M
iamGAUD said:
What will happen if i just put the block off plate on there without tuning it out from the car?
Will it just have poor fuel mileage or something else will happen?
Click to expand...
Without disabling the EGR function in the pcm, the pcm will keep trying to use the EGR Valve that is missing - it will not 'learn' or 'determine' that the EGR Valve has been deleted / blocked off.

Only reason why I can't tell you exactly what would happen is because I've never done it myself.
When I deleted the EGR Valve'n'stuff, I also disabled it in the pcm.
(I only tune OBD1 LT1s at this time.)

But even after you fix the crack in your throttle body elbow, you will likely experience drivability symptoms whenever the pcm tries and fails to use the EGR Valve that it still thinks is there - until you reprogram it.
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B
IIRC, on OBD2 it will turn on CEL. To what extent that affect engine operation, IDK if its the same as failing EGR system where it bogs on throttle tip in. But as noted the PCM is "looking" for its input which if it isn't getting because it has been plugged or deleted it effects engine operation.
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iamGAUD
Marky Dissod said:
Without disabling the EGR function in the pcm, the pcm will keep trying to use the EGR Valve that is missing - it will not 'learn' or 'determine' that the EGR Valve has been deleted / blocked off. Only reason why I can't tell you exactly what would happen is because I've never done it myself. When I deleted the EGR Valve'n'stuff, I also disabled it in the pcm. (I only tune OBD1 LT1s at this time.) But even after you fix the crack in your throttle body elbow, you will likely experience drivability symptoms whenever the pcm tries and fails to use the EGR Valve that it still thinks is there - until you reprogram it.
Click to expand...
Okay I understand now. I just need to find somebody who can tune an obd2 lt1
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iamGAUD said:
Im leaning towards just buying the back plate and leaving the check engine light on,
Click to expand...
Then the light can't ever warn you about other problems.

Blocking it/reprogramming the pcm only works if the EGR valve was bad and nothing else. Still have to make sure engine vacuum port/vacuum lines/solenoid aren't leaking.

EGR valve has to come off anyway, so why not pull it now and see if it's bad. If it's original from 1996, it's toast. Looks like maybe a not-recent Made in China replacement, which also probably is toast by now. :)
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1slow96
Why not just replace it with EGR for 6spd. F-Body, and call it done. That's what many of us did.
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95wagon
If I read this correctly, you have egr control disconnected so although it is in place it is not operating., correct ?

If so , try this , with the car cold start it up and hold onto the flex pipe from right hand exhaust manifold to intake.

If it stays cold , I submit the EGR is not leaking in the closed position and NOT the source of your running issues.

If it is getting hot then the EGR is leaking and COULD be causing running problems.

In that case you will need to either repair the system or block it off.

If not running EGR , tuning is important as the Calibration does throw a wack o timing at the engine at certain times.
Now does the timing get added when there are EGR related codes ? Dunno
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95wagon
And yes the F EGR requires less exhaust pressure to lift and was favorite among modified exhaust people that wanted to retain their EGR and turn their intake floor into a bbq ;)
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1slow96
Manifold vacuum opens EGR valves, not exhaust pressure
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95wagon
I'll give you a minute ,,,,,,,,,
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