Why Does My EGR Valve get Clogged Up?

About 17 months ago, my “check engine” light went on. I plugged in my code reader, and it indicated a defect in the EGR (exhaust gas recirculation) valve . I took it off, cleaned it up with solvent, and blew it out with compressed air, reinstalled, and reset the ECU. No problems after this…til last week. Same thing, I cleaned it and now everything is fine. The car is a 2002 Saturn 1.9 liter; when i changed the sparkplugs 13,000 miles ago, no indication of oil burning, absolutely clean. Should I get a new EGR valve?

Maybe replace the PCV valve?

Does your engine burn oil? If you are burning oil, that will cause a lot of carbon in your exhaust which will end up getting circulated back through the EGR valve and will clog it up.

If you are getting incomplete combustion in your engine, that will also cause gunk to build up in your EGR valve. Is your air filter clean? Any possibility of airflow restrictions?

Did the EGR valve seem particularly dirty either time you cleaned it? They’re always somewhat grungy, but actual problematic amounts of carbon build up are less common that the automotive folk wisdom of the enthusiast forums would have you believe. Do you happen to know what specific code was coming up? Were you having any symptoms other than the check engine light?

The EGR valve had some soot around the valve seat, nothing really heavy. The engine doesn’t burn oil at all-as i mentioned, the plugs were clean, with no deposits. the air filter is new; and the PCV valve moves OK. The last code tripped was P0404-EGR range incorrect.

In my Miata the pipe that feeds the EGR was super clogged, leading to a failure of the EGR to perform, the part was fine it just wasnt getting any flow.

You may want to check the values on your delta sensor, I think they call it an exhaust pressure sensor. Look it up on line and it will tell you what kind of output voltage you should be getting. I just had to change one recently getting the same kind of codes you were getting. Quite a few things can generate that code but if no blockages are present it will most likely be a bad sensor.

You might also find that the recirc gases also contaminate your air mass sensor - you would think that would not be possible, since the recirc gas rejoins after the air intake but there can be a kind of ‘drumming’ effect that can send a back pressure wave into the air intake, and along with it some oil residues.

You could stick an inline oil catcher in the air intake line- this will significantly reduce the amount of oil vapour making it back into the egr valve.

Final option, on some cars you can blank out the egr port and have the ecu reprogrammed, you’ll also get a noticeable boost in performance and fuel economy too

Are we talking about code P0401, which indicates insufficient EGR flow?

On my 1997 Ford Contour with a V6, when the code came up that indicated clogged EGR passages, it really wasn’t the EGR vale itself where the obstruction occurred.

The common place for such an obstruction to occur on the V6 Contour, and probably on almost every other car where this issue is relevant, is on some passages at the point on the intake manifold where the throttle body attaches to it. Remove the throttle body, scrape off the remains of the gasket, and look at the gasket surface on the intake manifold. Chances are, you’ll see that there are some gas passages on that surface, and chances are, you’ll find that they are clogged up with carbon deposits.

See my thread at http://contour.org/ceg-vb/forum/engines-drivetrain-and-power-upgrades/duratec-maintenance/1809650-p0401â—-cleaning-clogged-egr-passageâ—-pictures-that-i-hope-will-help-othersâ for pictures and a description of what I encountered when I tackled this issue.

Since this is GQ: No, you won’t gain fuel economy or performance by blocking the EGR. EGR is only active at part throttle, and shuts off at full throttle.

It recirculates some exhaust into the cylinders, and this lowers combustion temperatures (which lowers NOx emissions). Blocking it increases combustion temps and will often lead to pinging. There is no fuel economy impact either way.

The P0404 code is just the EGR valve itself reporting it’s not moving correctly. Since you’re not getting any other actual EGR performance related codes, and no driveability issues (right?) it could just be an electrical fault in the valve itself. It could be that just manhandling the thing off the car (and thus wiggling all the electrics) is what’s temporarily fixing it, not the actual de-coking. It could also be that the valve was indeed dirty after 14 years of service, and the offending bit of schmutz is somewhere that your cleaning isn’t going to be able to reach, but again the act of removing the valve and jiggling it is temporarily fixing it.

Either way, I think the combination of the clean spark plugs and the lack of any serious carbon build up seen on the second cleaning suggest to me that the problem is likely in the EGR itself (one way or another) and if the problem comes back replacing it would probably be a safe bet.