EGR blocked and drives fine...?

[mjm06]

Hello - first post for me, been lurking for years. I've been lucky enough to have used threads before to fix many Saturn issues, however, just can't seem to get this one (below) together... I currently have 3 road-worthy Saturns and one parts car...all gen 3 SL2's.

The problem one;
I have a 2001 SL2 with an automatic transmission, about 203K miles.
I bought this for my teenage daughter to drive, knowing that it seemed to transmission problems. After doing all of the "So far I have" things below, it still tachs too high before it will shift gears, seems to be hunting for gears, and shudders at some speeds once it does find a gear. However, I currently have the EGR (brand new) blocked with a cut-out from an old license plate....and it shifts awesome and does not shudder... Any pointers and/or advice, beyond leaving the EGR blocked, would be very much appreciated. Thank you!

So far I have;
-new/rebuilt valve body in transmission
-tightened both axle nuts
-new oil and filter in transmission
-new spark plugs
-new EGR valve, after cleaning old one and having same driving condition
-cleaned air hose that goes into exhaust manifold - was very clogged, but not 100%

[cdxhizors]

Originally Posted by mjm06

Hello - first post for me, been lurking for years. I've been lucky enough to have used threads before to fix many Saturn issues, however, just can't seem to get this one (below) together... I currently have 3 road-worthy Saturns and one parts car...all gen 3 SL2's.

The problem one;
I have a 2001 SL2 with an automatic transmission, about 203K miles.
I bought this for my teenage daughter to drive, knowing that it seemed to transmission problems. After doing all of the "So far I have" things below, it still tachs too high before it will shift gears, seems to be hunting for gears, and shudders at some speeds once it does find a gear. However, I currently have the EGR (brand new) blocked with a cut-out from an old license plate....and it shifts awesome and does not shudder... Any pointers and/or advice, beyond leaving the EGR blocked, would be very much appreciated. Thank you!

So far I have;
-new/rebuilt valve body in transmission
-tightened both axle nuts
-new oil and filter in transmission
-new spark plugs
-new EGR valve, after cleaning old one and having same driving condition
-cleaned air hose that goes into exhaust manifold - was very clogged, but not 100%

I had a 97 sl2 that had the same issue of shuddering when holding any speed above 25... The egr was replaced and eventually the front O2 sensor.. The O2 seemed to have fixed it. I think it has something to do with how it commands the egr open or closed. The O2 sensor is reporting that there isn't too much exhaust gasses coming into the motor so it allows more egr which causes the car to lean out but the faulty O2 doesn't see this so it doesn't report it. The check engine light rarely came on and when it did it was a code for egr improper flow..

[fdryer]

Unfortunately, egr valves in some situations demands only an OEM replacement. The engine computer sensing O2 signals determines when and how much to open the egr valve as one method to lowering combustion temperatures to control NOx emissions. Your simple test of blocking off the egr valve ports and perfect engine/xmission operation verified an incorrect egr valve. There are at least three incorrect ways egr valves fail; faulty stepper motors, faulty feedback position sensor, and sticking pintle valve not freely sliding to open close correctly. Wiring problems would be fourth.

Some states ignoring emissions inspection have members leave a permanent blocking plate on.

[ninetynineSC2]

Correct me if I'm wrong but, can't having it blocked at highway speeds cause the combustion temp to be higher than it is meant to be which could possibly burn valves? I remember reading that on a couple older threads.

[Signmaster]

Originally Posted by mjm06

Hello - first post for me, been lurking for years. I've been lucky enough to have used threads before to fix many Saturn issues, however, just can't seem to get this one (below) together... I currently have 3 road-worthy Saturns and one parts car...all gen 3 SL2's.

The problem one;
I have a 2001 SL2 with an automatic transmission, about 203K miles.
I bought this for my teenage daughter to drive, knowing that it seemed to transmission problems. After doing all of the "So far I have" things below, it still tachs too high before it will shift gears, seems to be hunting for gears, and shudders at some speeds once it does find a gear. However, I currently have the EGR (brand new) blocked with a cut-out from an old license plate....and it shifts awesome and does not shudder... Any pointers and/or advice, beyond leaving the EGR blocked, would be very much appreciated. Thank you!

So far I have;
-new/rebuilt valve body in transmission
-tightened both axle nuts
-new oil and filter in transmission
-new spark plugs
-new EGR valve, after cleaning old one and having same driving condition
-cleaned air hose that goes into exhaust manifold - was very clogged, but not 100%

Also keep in mind that if you have three Gen 3 cars, you have the advantage of people able to swap parts and see if the problem follows the part(s) changed, or stays with the car.

The EGR and/or O2 could be tested that way most likely, and point you in the right direction.

[cdxhizors]

Originally Posted by ninetynineSC2

Correct me if I'm wrong but, can't having it blocked at highway speeds cause the combustion temp to be higher than it is meant to be which could possibly burn valves? I remember reading that on a couple older threads.

That is a risk and is common... a blocked egr is what we suspect to have caused a burned exhaust valve on our 97 sl2...egr was immediately replaced after the head was rebuilt ...Though on the other hand, if you look up 4.3 w code vortec motors and their pages of complaints with egr problems you'll see the simplest and best solution is to block it...which my blazer drove for over 70k with a block plate

[fdryer]

Originally Posted by ninetynineSC2

Correct me if I'm wrong but, can't having it blocked at highway speeds cause the combustion temp to be higher than it is meant to be which could possibly burn valves? I remember reading that on a couple older threads.

Here's where it can become idle speculation for endless discussions about the pros and cons of burning exhaust valves. They burn up with egr valves in place and operating. How does that answer your question? Whether they cause burned valves without the egr valve operating is more speculation and the ones using the blocking plate haven't come back to report their engines burned exhaust valves........ Its well known that more burned valves are caused by leaned fuel mixtures due to intake manifold gaskets assembled incorrectly at factory assembly time as well as other issues like poor maintenance.

In theory, our EFI closed loop mode emissions control systems utilize the front/upstream O2 sensor to measure oxygen content that's fed back to the engine computer to continually alter the fuel mixture as close to the ideal 14.7:1/stoichiometric air to fuel mixture for tight emissions control. In the grand scheme of EFI systems, carefully feeding in exhaust gases alters the a/f mixtures and the O2 sensor detects it for immediate feedback to the pcm. Since the pcm is constantly monitoring O2 sensor signals, altering the egr valve feed of exhaust gases ultimately results in the EFI system still maintaining the ideal a/f mixtures while controlling emissions. Now block off exhaust gas flow altogether. Since the exhaust is still monitored by the O2 sensor, the lack of exhaust fed into the intake system implies a slightly leaner or richer a/f mixture that's still closely maintained to stay at stoichiometric. The lack of exhaust gases may affect or cause higher combustion temps in as much as higher or lower combustion temps is a change in oxygen use that's detected by the O2 sensor. Does anyone know how much higher combustion temperatures occur without exhaust gas recirculation? Is it a lot or a little? In effect, causing higher temperatures from less exhaust recycling implies a leaner a/f mixture that's compensated by the O2/pcm feedback circuit to maintain correct a/f mixtures.

Leaner than ideal a/f mixtures implies higher exhaust temperatures while rich mixtures implies lower temperatures. To go any deeper into combustion principles and correlating when exhaust valves supposedly burn up due to blocking off the egr ports would require more in depth discussions I'm not interested in. Suffice it to say that the members not complaining about burning their exhaust valves after blocking off their egr ports is good enough trial and error examples.

[mjm06]

Sincere thanks for all of the responses...!

One other thing i did last night, fyi; remove and clean the secondary air pump hose (goes into the exhaust manifold...it was ~90% plugged) and removed and checked the inline check valve, which was good.

The air pump did, when I bought the car (months ago), have water in it. I removed it and dumped the water out & re-installed.

Also, I'm not sure if this is important, however, will mention it. After turning the car off, there is a whirring sound....which sounds like something winding down. It's odd, and doesn't always happen, and my other gen 3 cars do not do this. It sounds like it's coming form the air pump?

So, per suggestion; I will pull one of the other known good EGR valves from a different car tonight to see if the problem goes away. I'm not hopefull, however, due to the fact that I had cleaned the one that was on the car (issues still present) and removed/cleaned/tested the one from my parts car too...which also did not fix the problem.