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EGR cleaning/diagnosing

10-27-2011, 11:07 PM
Ok seriously, does anybody know a truly effective way of cleaning one of these things or diagnosing whether it needs to be replaced? My check engine light has come on three times in the past year, and even though I'm pretty sure I've cleaned it as well as I can, I don't think I really even scratch the surface of what really needs to be done. And what the heck is a pintle? Where is the darn thing and how do I compress it? Anybody know where I can get a good tube brush with stiff bristles so I can get inside the thing to scrub it?
Current symptoms are that the engine is running a little more rough than usual, little more noise, and running a bit hotter than I'm used to (maybe a tic or two past half-way, which is where it usually stops). I think I'm also losing some gas mileage. Oh and the check engine light, codes P1404 and P0404. From what I've read, especially the engine running hotter than usual, I'm thinking the valve is stuck closed, and the EGR may be toast. That's fine, I just want to know and not revisit this issue again in 4 months!

Tech II
10-28-2011, 08:49 AM
Would help to know the year and engine size.....

10-29-2011, 08:51 AM
You can also do a Google ''Youtube DIY Auto EGR cleaning''

10-29-2011, 09:37 AM
Would help to know the year and engine size.....
Sorry! yeah that could be valuable. 1998 3.1 V6

10-29-2011, 02:40 PM
The pintle is the valve on the end of the plunger that seals the exhaust from the intake when EGR is not desired. The bottom of the valve has an open hole and a sealed hole. The seal is the pintle. It moves in and out to control exhaust gas recirculation into the intake to lower combustion chamber temperatures and reduce NOX emissions. The codes you mention set when the desired pintle position does not match the actual position. If the engine is running rough at idle the pintle may be stuck slightly open. With the valve removed the pintle should be easy to push in and spring back fully closed. If you remove it and it is open, or if you push it in and it sticks you will likely need a new one. When the valve is off, you can remove the throttle body to clean the tube that feeds the exhaust gas to the intake when EGR is desired. This may not be neccessary if you do not have insufficient flow codes but is a good practice. If you put a new one on you may want to disconnect the battery and touch the cables together to erase the previously desired pintle position and start fresh.

Tech II
10-29-2011, 03:25 PM
Only way to check an EGR is with a bi-directional scan tool, like the GM Tech II....

Depending on the car, some are vac operated, and some are electrically operated .......if electrical, some are three orifice EGR's and some are like your's, a linear EGR....

The linear EGR's have one pintle.....most codes are set when the "actual" pintle position does not match the "commanded" position.....this could be caused by a bad EGR, a bad pintle position sensor in the EGR, bad electrical connection/wire, or even carbon stuck under the seat.....

The way the pintle position sensor is checked, is with a scan command it by % to a certain opening, and the actual position should match the commanded.....

Some pintle position problems have been fixed by "reflashing" the PCM....

the other test is to close the valve with the scan tool...then slowly open it and feel the engine start to stumble as too much exhaust gas is introduced into the cylinders.....

The other problems an EGR has, is blockage....if the tube to the EGR is blocked, or the the passageway in the upper plenum is blocked, the MAP won't show a change in pressure when the EGR is opened, thus causing a code to set.....

11-01-2011, 10:05 PM
Well, I pulled the EGR and tried to clean it as best I could. The gasket didn't even get screwed up, so maybe I won't be out any $$ for this job. I found the pintle and checked it to make sure it moved properly. I had a new one so I could compare. On the old EGR it moved pretty freely, but when I pressed it all the way open it stuck a bit and I had to pry it up from underneath. I had some tube brushes and some carb cleaner, so I sprayed around inside and scrubbed, pressed and released the pintle several times. Not too much carbon came out, but there were a few chunks, and the pintle loosened up completely, so hopefully I'll be good for a while. I'm going to wait a bit before I take the new parts back though, just in case!

11-03-2011, 12:17 PM
The egr passage has a history of clogging up with carbon on those engines. I have had to clean many of them out in my days as a tech. The passageway goes from where the egr mounts to the intake and through a very small portal connecting into the intake plenum just behind the throttle body. You can remove the t/b easily and see where the carbon forms a little chunk in the inside wall of the plenum. I've always used a combination of a stiff wire bottle brush I bought off a tool truck, with picksets and carb/throttle cleaner and compressed air. I just keep reaming and picking at it till the cleaner disolves it enough for the pick to do it's job and
then the compressed air to blow it all out. Use caution with safety glasses of course. Once freed, you may need to get new t/b gaskets and egr. gaskets and finish up by clearing the codes. It sounds harder than it actually is if you can get the right tools and equipment. Good luck and hope this helps.

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