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P1406: 1996 Buick LeSabre EGR valve issue


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wildirish
User

May 20, 2019, 12:20 AM

Post #1 of 11 (342 views)
P1406: 1996 Buick LeSabre EGR valve issue Sign In

Last year, I had my EGR valve replaced.  About a month later, it started running rough, and threw the P1406 code.  Then the code went away, and the car ran more or less okay for several months.

Last month, the car started idling unevenly and roughly.  I had a gut feeling it was the EGR valve, and sure enough, I got the P1406 code again.

Thinking the EGR valve was defective, I replaced it with one I got at AutoZone.  The code went away and the car was running great for 2 weeks.  But the P1406 code is showing up again.

It's VERY hard to start the car, and when I do get it running, it runs so poorly that I don't think it would make it to the foot of my driveway.

I'm guessing that the valve is stuck open, since the symptoms are different when the valve is closed.

I don't have my tools with me to take the EGR valve off and see if it is fouled with carbon.  I still have the old one, and it doesn't look particularly dirty, but I'm just learning to do repairs, so I'm certainly no expert.

My question is, does it sound like the valve is getting fouled up with deposits, or is it a wiring issue?

I read on another forum that there is a gasket which can screen out deposits and prevent them from clogging the EGR valve, but I don't know if that's available for the 3800 series II engine.

I also read that some people were complaining that Seafoam had loosened carbon deposits, causing them to foul the EGR valve.  I don't know if this can happen or not, but for what it's worth, I did put Seafoam in my gas tank several weeks ago.

What advice do you have, and do you think this sounds like a problem with the wiring or with deposits?  I would think that the problem would be more consistent if it were the wiring, but as I said, I'm definitely no expert.

Any input would be appreciated.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

May 20, 2019, 1:10 AM

Post #2 of 11 (336 views)
Re: P1406: 1996 Buick LeSabre EGR valve issue Sign In

Codes + Autozone. They don't mix well but got you to buy an EGR valve so that worked.
Back to the issue is it runs rough at idle says enough. EGR is or should be off and sealed at idle really shouldn't be the cause of a problem unless leaking any which way.
With that there's also other things nearby to leak probably the real current issue so try to find a vacuum leak first. 1996 already a dinosaur by age is open book on start with something but NOT tossing parts.
Hey, glad you kept the old one there's probably nothing wrong with it take the new one back later if we can find out where the root problem is. Vacuum leaks first hard to isolate try and report back there would be many ways if frustrated with just check for those,




T



Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

May 20, 2019, 3:56 AM

Post #3 of 11 (331 views)
Re: P1406: 1996 Buick LeSabre EGR valve issue Sign In

Yep, sounds like your whole problem is carbon. It is breaking off in chunks and getting caught in the EGR valve since you loosened it with the sea foam. The valves aren't bad, they are just the victims of the carbon. I have heard of those screens for the EGR but never used one. It would be the solution if you can find one for your car.
It may also help if you took the car out and really blasted it. Foot to the floor, wind out the gears to flush out as much of the carbon that you can. You may have to remove the valve and clean it out after that.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



wildirish
User

May 20, 2019, 8:12 AM

Post #4 of 11 (314 views)
Re: P1406: 1996 Buick LeSabre EGR valve issue Sign In

It wasn't just AutoZone. The mechanics were talking about replacing the EGR valve to the tune of $300-$500, which is why I decided to do it myself. I'll be sure to report back when the cause of the issue is found.


wildirish
User

May 20, 2019, 8:16 AM

Post #5 of 11 (312 views)
Re: P1406: 1996 Buick LeSabre EGR valve issue Sign In

Your suggestion sounds like a good idea, except that I can barely get it to start, let alone run. But I do think you're right, focusing on unclogging the EGR valve. The catch is that I need someone to give me a ride, so I can get my tools back and . I've seen videos on YouTube showing how to clean out an EGR valve.

So I'm going to try that, as soon as I can get transportation. Thanks.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

May 20, 2019, 8:20 AM

Post #6 of 11 (308 views)
Re: P1406: 1996 Buick LeSabre EGR valve issue Sign In

The EGR is not the cause of your "no start" problem. It can give you the rough idle and stalling at idle but that is it. You have another issue going on there.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



(This post was edited by Hammer Time on May 20, 2019, 8:21 AM)


wildirish
User

May 20, 2019, 4:18 PM

Post #7 of 11 (287 views)
Re: P1406: 1996 Buick LeSabre EGR valve issue Sign In

I cleaned the EGR valve a little, and the car starts/runs fine for now. It looks as if the EGR valve is getting fouled up with carbon, so I've got to clean things up better when I have time. I know I've only made a temporary fix.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

May 20, 2019, 4:29 PM

Post #8 of 11 (282 views)
Re: P1406: 1996 Buick LeSabre EGR valve issue Sign In

That still isn't your starting problem.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
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May 20, 2019, 11:58 PM

Post #9 of 11 (266 views)
Re: P1406: 1996 Buick LeSabre EGR valve issue Sign In

Starting problem? Just a hunch now. There should be a CTS (coolant temp sensor) I think all GMs used a black and yellow wire to plug on the sender would fail. No codes would show for it but car was delivering fuel and adjustments as if warm or cold when not was the culprit. That or the plug itself right there.


It just adjusts the voltage thru it for the given temp of the engine at the time super cold thru fully warmed up. If unable to read this or wrong thermostat can be the root cause of what's going on switching from thinking it's cold to warmed up.


The first possibly most common reason is putting in a 180F thermostat (now or some time ago) to keep engine cool is an error to vehicles much older than this.
It's hard to rule this out without just tossing thermostat by the time you see its markings you are there anyway.


Some got replaced and over use of Teflon tape on the thing it couldn't work dependably give you fits like this but the signal sent is credible but wrong so would not start or not start well!


That's a guess of a mistake both techs and DIYer would make using wrong thermostat ends up the root cause possibly years later of the problems now.


It's near impossible to know exact rating of the thermostat or if its accurate so easily. If you do this just make sure you've purged air out of cooling system for sure it doesn't require emptying it totally just lower it some.


A guess that has been the reason for whacked things like what was seen at the EGR as dirty crust at the pintle,


T



wildirish
User

Sep 6, 2019, 2:42 PM

Post #10 of 11 (75 views)
Re: P1406: 1996 Buick LeSabre EGR valve issue Sign In

Update: The problem seems to have been solved, when a mechanic cleaned things out with compressed air. The car hasn't thrown the P1406 code in over 2 months.

It was starting fine for several weeks, then on some very hot days, it took longer than usual to start. That *seems* to have been solved by replacing the fuel filter. The fuel pump was tested, and it's working fine.

Some mechanics thought a clogged catalytic converter might have caused the EGR valve issue. I just had it tested last week, and while it's a little blocked, it's well within normal limits. So that wasn't causing the EGR valve problem.

So now, the only problems left are an exhaust leak that was found, and a slightly rough idle. The mechanic thinks the MAF sensor may need cleaning, but that's a story for another post, if that can't be rectified easily.

Thanks to all who replied to my original post!


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Sep 6, 2019, 2:50 PM

Post #11 of 11 (69 views)
Re: P1406: 1996 Buick LeSabre EGR valve issue Sign In

Yep, that's what i said in my first post.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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