Haunted by the EGR...

[Orkin]

Okay, it all started about a year and a half ago...when I bought my SHO. The CEL would come on every now and then, so I checked the codes...332 "EGR valve opening not detected". I checked here, saw it could be clogged EGR nostrils. So I cleaned those out and fixed the broken EGR line, and I had no CEL for over a year.

Then oh...4 months ago, I started getting a CEL again...checked the codes...335 "DPFE sensor voltage higher or lower than expected". So I replaced the DPFE sensor. Went fine for a few months.

Then the CEL came back. This time 332 again. I've checked around, the nostrils are fine, the hoses going to the EGR look good, I just replaced the DPFE sensor...

My question is, what else could cause the 332? Could it be the actual EGR valve this time? Or is there some other part involved in this nightmare of emissions controls?

Thanks,
Orkin

 

[rangerj]

Did you clean the opening in the intake manifold and the exaust manifold? Is the EGR poppet valve opening and closing? Are the vacuum lines to the DPFE and EGR valve clear of any blockage, or are they leaking vacuum?

 

[Markus]

It's not just the nostrils. I found the long tubes EGR within the intake that lead to the nostrils also clog up. IIRC the only way to clean them is to remove the intake and remove the hex plugs at the end of the passageways. The hex plugs are a bugger to get off - really needed a cheater bar for mine. This might be a good time to clean the entire inside of the intake.

 

[Dan H]

A nice peice of black tape will fix that annoying CEL light right up.

 

[Orkin]

I found the long tubes EGR within the intake that lead to the nostrils also clog up...This might be a good time to clean the entire inside of the intake.

Which is exactly what I spent 7 hours and 7 cans of B12 on last Saturday...trust me, it's all clean.

I double-checked all the vacuum tubing, no leaks, no blocks. I'm starting think it's gotta be the valve itself...

 

[SHOZ123]

If you apply vacuum manually to the valve while the car is idling it should stumble or die if the valve itself is working.

 

[Orkin]

Okay, I tried applying vacuum to the valve by connecting a hose directly from the valve to the small vacuum port on the back of the intake manifold, bypassing the vacuum regulator, and the idle got noticably rougher, but nowhere near enough to cause it to die. Should it be stumbling enough to **** the engine?

Could it be the EGR vacuum regulator? Is there any way I can test it?

Thanks for the help!

 

[SHOZ123]

Yes it could be the regulator. Do you have a vacuum gage? When the car is at operating temp and the engine speed is ~2000 rpm the valve should be partially open.

Another way to see if it is being opened under normal operating conditions is immediately after some highway driving see if the EGR valve base or tube leading to it is too hot to touch. This would mean it is working.

I do not have the correct diagnosis procedures here at work to give you.

Later tonight when I get home I can post them for code P332

 

[projectSHO89]

Applying direct intake manifold vacuum to the EGR valve should have completely killed the engine.

For whatever reason, you do have low EGR flow. If the nostrils and the entire intake tract are completely clear, that only leaves the EGR valve itself. While rare, they do fail.

I'd pull the EGR valve and maually test it (milkshake test) to see if the poppet is properly moving. Also, verify that the diaphram is holding vacuum.

Steve

 

[rangerj]

While you have the EGR valve out check to see if the opening is clear of carbon build up. This is a more common cause of EGR problems than failure of the vacuum diphram. You may have some luck with cleaning the valve around the opening but it is almost impossible to get it really clean.

When you check the valve movement with an external source of vacuum be careful not to exceed 10hg of vacuum. Excess vacuum can ruin the valve diaphram.

 

[Orkin]

Okay, this may be a stupid question, but do I have to remove the entire EGR assembly (valve and pipe) to get the EGR valve off? It looks like it will be a pain getting the bolts to the exhaust manifold out...

 

[rangerj]

Yes. Remove the EGR valve and the pipe. Check the pipe for carbon build up and the opening in the intake and exaust manifolds. Then check the EGR valve. And yes the exaust manifold bolts can be a pain, but there is no other way to inspect and clean the parts. There are gaskets at the intake and exaust end.

 

[Markus]

Yes. Remove the EGR valve and the pipe. Check the pipe for carbon build up and the opening in the intake and exaust manifolds. Then check the EGR valve. And yes the exaust manifold bolts can be a pain, but there is no other way to inspect and clean the parts. There are gaskets at the intake and exaust end.

A few questions for you. When I removed the EGR assembly the tube at the ****** that attaches to the exh manifold has broken off from the ******. I didn't weld mine back on for 2 reasons. Firstly, the tube lloked like it had been tack welded to the ****** in one small area and therefore there was not a complete seal between the tube and the ******. Secondly, when I bolted the assembly in place the tube fit perfectly inside the hole of the ****** and there really is no noise from the ****** when the engine is running.

Questions:

1) When originally installed new, was there a seal (a complete weld) between the tube and the ****** at the exh manifold?

2) If the answer to Q1 is "no", then the gasket between the ****** and the exh manifold is not really needed, right?

 

[rangerj]

1. The tube is flared and this provides a seal between the tube anf the ******. The seal between the ****** and the exaust manifold is provided by a gasket.

2. No. the gasket is necessary as the surfaces of the ****** and the manifold are not a fine enough machined surface.

 

[dagcakes]

Markus:
what size were the bolts holding the tube to the manifold? I need to remove mine soon. How difficult was it to remove?

 

[Markus]

I don't recall the size of the bolts. I do recall that they came out very easily. The end of my tube was not flared - I don't know why.

 

[Orkin]

I finally got around to pulling my EGR valve and tube. Man were those bolts a pain to get to! Anyways, the EGR valve appears to be opening and closing as it should, and all the passages appeared to be clear. I went ahead and sprayed the whole thing out with B12 to be sure...but I'm still getting the 332!

I checked a little more closely into the EGR vacuum regulator. There's a VERY slight vacuum coming off it at all times. After letting the engine warm up, the vacuum appears to increase when I rev the engine to 2k RPM, but only slightly. It doesn't seem to be enough to open the valve anyway. Is there a more thorough way to check the vacuum regulator?

I'm about to give up on this...I just hate to have my CEL rendered useless...

Thanks again,
Orkin

 

[Markus]

I finally got around to pulling my EGR valve and tube. Man were those bolts a pain to get to! Anyways, the EGR valve appears to be opening and closing as it should, and all the passages appeared to be clear. I went ahead and sprayed the whole thing out with B12 to be sure...but I'm still getting the 332!

I checked a little more closely into the EGR vacuum regulator. There's a VERY slight vacuum coming off it at all times. After letting the engine warm up, the vacuum appears to increase when I rev the engine to 2k RPM, but only slightly. It doesn't seem to be enough to open the valve anyway. Is there a more thorough way to check the vacuum regulator?

I'm about to give up on this...I just hate to have my CEL rendered useless...

Thanks again,
Orkin

A slight vacuum through the regulator at all times is normal. When I get home (tomorrow) I'll dig up my diagnostic routines for you.

 

[Markus]

I finally got around to pulling my EGR valve and tube. Man were those bolts a pain to get to! Anyways, the EGR valve appears to be opening and closing as it should, and all the passages appeared to be clear. I went ahead and sprayed the whole thing out with B12 to be sure...but I'm still getting the 332!

I checked a little more closely into the EGR vacuum regulator. There's a VERY slight vacuum coming off it at all times. After letting the engine warm up, the vacuum appears to increase when I rev the engine to 2k RPM, but only slightly. It doesn't seem to be enough to open the valve anyway. Is there a more thorough way to check the vacuum regulator?

I'm about to give up on this...I just hate to have my CEL rendered useless...

Thanks again,
Orkin

I have a 26 page Word document ready to go for you. PM me with your email address and I'll send it to you.

 

[SHOZ123]

There should also be a vacuum solenoid valve. This would be before the regulator. It turns the vacuum on and off.

At idle the vacuum solenoid should be off and there should be NO vacuum going to the EGR valve. As engine speed increases the solenoid comes on and then regulated vacuum is fed to the EGR valve.

The DPF EGR sensor calculates the flow of exhaust gas solely as a check for actual EGR valve operation.

Here is some boring reading....

http://www.asashop.org/autoinc/dec97/egr.htm