EGR help!!

[Z31toZ32]

Well, I am moving to Texas which requires emissions and tried to get the 98 Max (DD) ready to go. I replaced the EGR valve with an OEM one, which removed the check engine light.

2 weeks later and a week before I move to Texas, the check engine light is back on!! I am getting code P0400, which again is the EGR. Below are causes of the P0400 code:

* Plugged EGR passage which restricts the flow of exhaust gasses
* Faulty EGR solenoid
* Faulty EGR solenoid wiring/harness
* Vacuum lines damaged/disconnected to the EGR valve solenoid or to the EGR valve
* Faulty EGR valve

What do you think I should do, any advice? I haven't gotten under the hood yet, but I am hoping a line just popped off somewhere. Anything that is known to pop this code? The EGR should be good, and unblocked.

Thanks.

[NutriaforBreakfast]

Search 1995 maxima egr
I posted a lot of stuff there

[NutriaforBreakfast]

Have experienced this trouble code problem before. It is complicated. And you have
to work on the problem while the engine is hot most of the time to see if the EGR valve
works. My EGRC was colored green and was pretty close to the top of the engine toward the
top radiator hose. I think there are two vacuum lines; one goes to the throttle body? and one
goes to the EGR -BPT valve

READ HERE FIRST!
http://www.nicoclub.com/FSM/maxima/1995/ec.pdf
Page 130 and continues

Check and see if your EGR valve is working first. When you rev up the engine
you should feel the diaphram of the valve move. USE GLOVES ITS HOT! If not it is either stuck in the
open or closed position. It is is stuck closed, you car is probably running ok -maybe.

You might have a hose that is split so check your EGR hoses first. If you have never changed them
go to the dealership and get the right size cause Auto Zones were too loose or not heat resistant
(no I dont use windshield washer fluid hoses on the engine). I put a LITTLE gasket sealer around
where the OEM hose slips on to the male slip on extension (to make it airtight).

Generally speaking, your EGRC solenoid activates the EGR-BPT valve which works and activates with
the EGR valve. You also have a temperature switch for the EGR system and it needs to work too.
There are hoses coming from the solenoid and working with the throttle body too. I think the EGR temp
switch sends a signal to the ECU. The ECU then triggers the EGRC solenoid to switch vacuum on and off.
So if your not getting vacuum to the EGR valve then either the component/s mentioned are broken
or carbon is stopping the exhaust flow.

If you have never cleaned carbon out of the EGR tube (goes from EGR valve
to back of plenum by firewall) you might start there.

I "fixed" mine but probably the least cost effective way. I already had on a new EGR
valve so I added new hoses, a new solenoid valve , new temp switch, and a new EGR-BPT valve and the CEL went away.(I really think the solenoid was ok but I changed it). I was just trying to pass inspection and
I figured if they held it up it would cost me about $300 (of shop labor) which is what I paid for new parts anyway. So I think my EGR valve is stuck closed (it wont move I think, not at idle or revving up) but hey no CEL and passed inspection. And I replaced the parts because it was just too hard to test them and put the car back together to do so. I figured the shop would kill me with labor for a 50 dollar part.

You might try a search of this website to see what else you come up with and Chiltons will help
too.

Good luck!NutriaforBreakfast


Posts: 823
Joined: 26 Sep 2007 12:41
Car: Nissan Maxima 1995 VQDE engine

[Z31toZ32]

thanks a lot for the advice! hopefully i figure out this SOB before it burns a hole in my wallet.

[tigersharkdude]

a little late here, but check the EGR flow tube that connects to the back of the UIM (it mates to the UIM under/beside where the IACV is). The port in the UIM for the EGR tube often times becomes clogged with carbon buildup, and doesnt allow enough air to pass through.

Does your CEL ever turn off? If so, it may be because sometimes when the air does pass through the port, the EGR will recognize it as being "enough", while other times the EGR will not. Clean the flow tube and the port, IMHO thats usually what the P0400 code is

[Z31toZ32]

a little late here, but check the EGR flow tube that connects to the back of the UIM (it mates to the UIM under/beside where the IACV is). The port in the UIM for the EGR tube often times becomes clogged with carbon buildup, and doesnt allow enough air to pass through.

Does your CEL ever turn off? If so, it may be because sometimes when the air does pass through the port, the EGR will recognize it as being "enough", while other times the EGR will not. Clean the flow tube and the port, IMHO thats usually what the P0400 code is

UPDATE: The CEL light never turns off once it clicks on. I have noticed that if I reset the ECU, if I drive mostly on the highway, the light will stay off for 100-200 miles, depending how much city I have mixed in. If I am entirely city, particularly sitting at lights, the P0400 will pop within 20 miles, 30 at the most. Does that help a diagnostic at all, or still at square one?

I think my next step is to try and clean out the flow tube... btw is the EGR flow tube the larger metal tube that flows the exhaust essentially into the the EGR valve? Can I get to this from underneith the car? If I have to get at it from the top, I was thinking of just buying a new solenoid, temp sensor, vaccuum hoses, etc., and cleaning it out all at once, since I'd have to do some dis-assembly to get at that bi***. Thanks for the input here everyone. Although the engine light is still on, I feel like I am finally getting to the bottom of the problem.

[maxhopper]

I support your mass replacement approach(all components,vacuum hoses,etc). It's always best to take care of problem in a broad spectrum, unless you can accurately identify the problem in a specific system. The EGR stuff is going to be easier to work on from the top of the motor, not the bottom (the EGR valve is located under the throttle body area).

[Z31toZ32]

Alright, so just to be clear, here is exactly what I am going to buy after I borrow some ov-gloves and make sure the EGR valve is pumping while revving:

EGR Valve Solenoid
EGR-BPT valve
EGR Temperature switch
EGR hoses

and clean the EGR flow tube...

Can someone please double check my parts/plan of attack? Any recommendations on where to get the parts? Will new non-OEM parts work okay? I figure even though the flow tube is most likely blocked, since I have to take all that crap apart, I might as well replace all that crap while I am in there. If I don't pass after this, I may lose my mind.

[Z31toZ32]

well, i went back and somehow passed emissions without doing a damn thing. how the emissions works here in houston is that it is an odbII check. you can't have a check engine light on, and depending on how old your car is, it can either have 1, 2, or 3 systems "not ready." i was popping a p0400 which is the egr. i came to realize that this code dosen't pop until several hundred miles on the highway, but as soon as i idle in the city for awhile, it pops immediately... so the challenge to beat the system was to drive around enough to arm the rest of the systems and not "pop" the egr. welp, that is what i did, and when i was in the city, i either kept the rpms up by downshifting, or turning the car off and only starting it when i got to the station. and, it worked somehow. after about 100 miles of highway driving after an ecu reset, everything was armed except the EGR, which for a 98, that was good enough to pass. the CEL came on on the way home... so i am good for a year. not sure if i will do the work on the car, or if i will just dump it over the course of the next year for a mid 80s mercedes turbo diesel assuming that i can come across a decent one. thanks for your help everyone.

[bvgetiw943]

Congrats on passing inspection! If you decide to go back and remove the EGR tube and clean it, check out this link:

http://forums.maxima.org/4th-generation ... p0400.html

I followed these instructions and was able to remove the egr tube and clean the tube, as well as the area inside where the IACV goes in. DO NOT FORGET to clean the area inside the IACV where the EGR tube connects. This area will also be clogged with carbon.

Also, the idea about laying a board across the engine was extremely helpful. I was able to complete this job in a weekend and my engine light has been off ever since.

If anyone has any questions/clarification on how to do this, let me know

[Z31toZ32]

wow great write up. i might end up doing this after all, should i decide to ride the car out! it is literally rusting to pieces so i figure i might want to look into a new dd one of these days.