[100]

I just wanted to share the information.

I have been having a knocking problem since I bought my 95 Sedan DeVille (4.9). I thought I needed some tune-ups. I have done many so-called basic tune-ups and even more, but I couldn't fix. Some of those repair made the car run better, but none got rid of the knocking problem...

Well, finally, I replaced the EGR valve and it fixed the problem! I am so happy.

No one here reported faulty EGR valve as far as I know, but it does break (not just clogged, but break). I had good vaccum right at the EGR valve, EGR solenoid was fine, I could activate the EGR valve by my finger to stall the engine at idle... So, I thought the EGR system including the valve was fine for long time. But finally I came to the conclusion that the EGR valve was not working properly, because there is no other reason I could think of! So I replaced the EGR valve. I had to grind a 13 mm socket to make it shorter to fit under the head of the valve to remove the bolts, but once the tool was ready, it was a simple job to do. After removal, I checked the valve. The EGR valve looked fine and seemed to work fine with my finger, but when I shaked it, it made funny noise in the head of the valve. Sounded like there were some pieces rattling in it. I don't know what they were. Anyway, since the valve looked OK except that rattling sound, I was wondering if it really fixed the problem. But it did.

I didn't know that 4.9 has such a wonderful acceleration and fuel economy!

 

[adalla]

Yes, my EGR valve looked pretty good too, and I hoped after cleaning it would eliminate the knock, but it did not. Despite there is an opinion th EGR valves are booletproof on 4.9 they are not. If you do not have right customized tool you have to remove the throttle body to get access to EGR valve's bolts.

Good job! That knock is definitely annoying. There did you get the part and how much did it cost? And you probably replaced the gasket too.

 

[ewill3rd]

There is a diaphragm inside the valve. After many years they can develop pinholes or cracks and even if everything is working, the vacuum won't lift the pintle because of the leaks.
EGR helps reduce Oxides of Nitrogen or NOX by cooling the combustion chambers by reintroducing inert gas in the intake manifold. When combustion temperatures get too high you get NOX and do to the high temps you get precombustion. This is what we call "pinging", and 4.9 liters do it bad, I mean real bad, when the EGR valve doesn't work anymore.

I have seen a couple of these recently, one left happy, one left with the worst pinging I have ever seen. He didn't want to pay to get it fixed.

Glad to hear you got it fixed.

 

[100]

If you do not have right customized tool you have to remove the throttle body to get access to EGR valve's bolts.

I think (of course I dont know for sure, because I didn't do) it may require the removal of the thermostat housing, too. The bolt on the driver side seemed to be difficult to be removed if the thermostat housing is in place.

There did you get the part and how much did it cost? And you probably replaced the gasket too.

I got the new EGR valve at Murray's auto (cheap stuff...) for like a bit less than $60. But the one I got came with many little orifices and you have to install it in the EGR valve. It is not easy and I wouldn't recommend to buy it. Well, but it came with a new gasket. In my opinion, buying the genuine EGR valve would be the best way to go.

 

[adalla]

Thanks 100. I'll replace mine next year - sick and tired of the knock when engine is hot. LOL
BTW, I have got two gaskets for EGR valve. If someone need one I can mail (free of course).

 

[100]

one left with the worst pinging I have ever seen. He didn't want to pay to get it fixed.

I felt like my engine was going to break if I didn't do anything. So, I retarded the timing to get rid of it until I fix the problem. But when I adjusted the timing so that almost no pinging was audible, the performance was pretty bad especially during acceleration. This made me to pay $60 (well, money was not a problem, but finding the cause was the problem..).

Well, anyway, the engine is now fine!

 

[100]

I'll replace mine next year - sick and tired of the knock when engine is hot. LOL

Well, it was a very simple job. But the most difficult part was to get the right tool... Otherwise, you may have to remove a lots of other parts... Good luck with you.

 

[chevelle]

Just out of curiosity did you check/clean out the EGR tubes underneath the throttle body??

Was the EGR valve an OEM part or a generic aftermarket replacement part?

If you haven't checked/cleaned the EGR tubes it is still adviseable as they can clog and cause loss of adequate EGR flow under all conditions.

EGR valves do fail on occasion but in most all situations where spark knock or ping is an issue the problem can be traced to the EGR tubes being plugged, not the EGR valve itself being failed. That is why the first step is to clean the tubes out and see if it solves the problem before the EGR valve itself is replaced.

 

[100]

Just out of curiosity did you check/clean out the EGR tubes underneath the throttle body??

Yes. They have been clean.

Was the EGR valve an OEM part or a generic aftermarket replacement part?

I am not sure, well, it was not an AC Delco-made part (I don't remember the manufacturer name...). You may call it a generic part. It came with many orifices that you need to select according to their instruction and attach it in the EGR valve. Since I was able to use a spotwelder, it was OK, but I would not recommend to get a generic part, as I said in the previous post.

EGR valves do fail on occasion but in most all situations where spark knock or ping is an issue the problem can be traced to the EGR tubes being plugged, not the EGR valve itself being failed. That is why the first step is to clean the tubes out and see if it solves the problem before the EGR valve itself is replaced.

Yes, you are absolutely right. I just wanted to say that sometimes there is actually the "second" step to solve the problem, since I have never seen anyone reporting their EGR valve failure...

Anyway, thanks!