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Keith4358
Novice
Aug 13, 2006, 9:26 AM
Post #1 of 5
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98 Monte Carlo EGR valve
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I have a 1998 Monte Carlo LS 3.1 V6. The fault code is P0401. EGR flow is insufficient.
Can anyone tell me where the EGR valve is located on this vehicle and if it is a diy type job or should I have a mechanic do it.
Keith4358 
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 13, 2006, 4:40 PM
Post #2 of 5
(8144 views)
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Re: 98 Monte Carlo EGR valve
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It should be high on the engine and near air intake/throttle body. Some can just be cleaned up. Get a new gasket and use high temp grease on it with clean surfaces and you can use it again without a problem but use that sparingly. Just a smear no more, and then if you do replace it with new it'll make it much easier, T
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Keith4358
Novice
Aug 13, 2006, 9:51 PM
Post #3 of 5
(8141 views)
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Re: 98 Monte Carlo EGR valve
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How would I go about cleaning up the valve?
Keith4358 
(This post was edited by Keith4358 on Aug 13, 2006, 9:53 PM)
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DanD
Veteran
/ Moderator
Aug 14, 2006, 4:38 AM
Post #4 of 5
(8137 views)
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Re: 98 Monte Carlo EGR valve
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Code P0401 as its description; is set because of insufficient flow; during a test that PCM (powertrain control module) will perform during a moderate deceleration. Anytime that the engine is up to temperature and there are no other codes stored. The PCM will run the test by opening the EGR when the vehicle is above 20 miles per hour, your foot is off the throttle and you are coasting. As the PCM opens the EGR it monitors the MAP (manifold absolute Pressure) (engine vacuum) sensor readings. IF the PCM doesn’t see the expected change in readings it will store the code and turn on the MIL (malfunction indicator lamp).
What you have to check for is whether the PCM still has control of the EGR, is the EGR still capable of opening, are the EGR passageways not clogged restricting exhaust flow and whether the MAP sensor is capable of responding to a quick change in engine vacuum. So other then checking for blockage in the passageways, you’re going to need a scan tool to perform most of the tests.
A scan tool is a lot more then a code reader. A quality scan tool has bi-directional capabilities; which the operator of the scanner can request the PCM to perform certain functions. In this case request the EGR to open and to open to certain requested percentages.
As for cleaning an EGR valve, in my opinion is a complete waste of time, if it sticks open or closed once it’ll stick again. There’s always an exception though, if the EGR is stuck due to a piece of hard carbon. Carbon that can be removed without the use of solvents then you may get away with cleaning it. Again this is just my opinion but once you introduce solvents to a GM linear EGR valve you’ve just written its death sentence.
There is one other possibility for the cause of the code being set and that is there maybe a reflash for the PCM. A PCM reflash is GM’s way of saying oops and they have changed the programming of the PCM to compensate or open up the perimeters of the test so that the code will not set. In other words there may not be anything wrong with the vehicle that a “reflash” won’t take care of.
Again you will need a scan tool to retrieve the calibration code (program number) that your PCM is using.
Then go to this site http://tis2web.service.gm.com/tis2web
with the VIN number of the vehicle. Enter the VIN and the site will give you all of the updated calibration codes (programs) that GM has come up with to cure different issues for this vehicle. If there are up dates you’ll have to take the vehicle or the just the PCM into a dealer or someone that has the equipment to perform the up dates.
Dan.
Canadian "EH"
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 14, 2006, 9:13 AM
Post #5 of 5
(8131 views)
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Re: 98 Monte Carlo EGR valve
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Dan just posted an awesome description of the whats and what's best. I have had some luck with getting carbon crust out of EGR valves and they were older vehicles. They had demonstrated idling problems as they should be off when idling. If they can't seal shut a car can stumble at idle and may be fine driving along.
The cleaner I used was Carb/throttle body cleaner and it WAS a last ditch effort to save some bucks.
Hey if Dan said it can cause problems go with that. I had a time with my own car a 1989 that failed by the slightest on NOx only and ended up with a new EGR and the damn thing on retest was a little worse
My state is terroristic about emissions and they don't like older cars and I do so we have problems! Hey, Good luck with the fix, T
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