I am getting p0400 and p 0402 codes. checked the egr valve works fine. checked egr solenoid for resistance and it is fine. no lines are clogged. the code comes back. i am only getting 4 volts to the egr control solenoid instead of 12.6 or something? when i feel the diaphragm of the egr valve it moves a little bit when i rev the car. dont know what elese could be wrong. it idles rough sometimes and it jerks sometimes, like hesitates on high speed sometimes. it stalls out on idle sometimes too. it is a 98 maxima 5 spd. any help is appreciated. thank you

Check the EGR air passage tube again.

You may miss some on the first pass.

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Check for

vacuum leaks on intake manifold,

the air tube between the air filter.

intake manifold vacuum hose.

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clean throttle plate with Berryman carburator cleaner

SEE sample picture HERE
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Also remove carbon built up behind the EGR valve and the EGR passage tube.

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Vacuum leak WILL offset the intended 14.7 to 1 air fuel ratio.

More un-metered air (leaks) will lean out the fuel mixture.

Use small amount of Berryman carb clearer at potential air leak area will help you identify trouble spot.

At idle,just spray and listen for the RPM surge.

The in-rush of carb clearer will increase the RPM on the motor.

Record the problem spot(s) and address it later.

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EGR carbon built up require 2+ hours to clean from start to finish.

You will need a new EGR base gasket before your start.

Locate and remove the EGR valve after the vehicle is cool down.

Carefully record the connector and vacuum line (for older vehicle) location by drawing an easily to follow diagram.

Remove the EGR valve.

Inspect the location of the carbon built-up inside the valve and the EGR passage tube.

SOAK these areas with WD-40 spary.

You will need a small screwdriver,cloth hanger and lot of newspaper and time to get this cleaning done right.

RE-SOAK the carbon and let it sit for over-night will also help.

One the last round,pass a shop vacuum of the EGR valve and the passage pipe.

Install the new EGR gasket and connectors.

Allow the vehicle to warm up outdoor to burn up any remaining WD-40.


Take it for a test drive.


Please rate my answer if it's useful to you.


Cheers,

Mustgo

Thanks Jay for your interest.
I had one question though, am i supposed to get 4 volts at the egr control solenoid on ignition. is there any otheer way to check the control solenoid? I dont want to replace it and the problem come back again. and is the egr tube the thick tube with a big bolt attached to the egr valve? if yes i checked that and there was no clog. I really appreciate your help.
ps the problem is worse now and it stalls almost at evey traffic light. :(  

Hello and thank you for using Fixya!

I know you say there is nothing clogged. How ever, it's very common to get a Egr code P0400 when the egr tube is clogged. Remove just the Egr tube, the one with the egr temp sensor. Remove the EGR temp sensor and remove any carbon build up in the pipe. Then make sure the passeges in the intake are clear also.

If you have any more questions on this, please feel free to ask. Thanks Jay!