1990 Corvette 5.7 TPI Chasing a DTC32
I wonder if anyone can help me, I'm chasing the infamous Code 32. I've changed the EGR Solenoid and the EGR Valve which was hanging up. I drive with a vacuum gauge T'd in just before the EGR valve and do not see any change in vacuum while driving at 65 MPH. Vacuum holds at 10" when the code comes in. I've gone through the test documents with the flow charts and diagrams. Everything seems to test ok. It comes in after the car is driven for a while and clears itself after cool down. Vacuum lines appear ok.
I have seen a post recommendation on an 85 model where the trouble was cleared by placing a one way check valve from NAPA (730-1347) in the vacuum line from the plenum to the EGR solenoid. I think I would like to try this but am not clear about (Plenum to EGR solenoid). I wonder if he means between EGR Valve and EGR Solenoid? Does anyone have any information on this fix?
I would greatly appreciate any help with this.
Thanks!

 

Maybe you have a funky EGR temp switch.

 

If you have done any Exhaust mods, like headers for example, some are just plagued by the dreaded code 32. Solution I used was to get a Moates Ostrich and disable the code in the ECM!

 

No exhaust mods have been done, just new EGR Solenoid and EGR Valve.
BTW, I have also seen reference to a EGR Temp Switch, I have looked all over this car for it and can not find it. I wonder if this has been eliminated on the 1990 car with the 5.7 TPI engine?

I really appreciate the help!

 

Isn't the EGR temp switch the one sitting IN the EGR pipe....the one the runs from the manifold, over the PS valve cover, to the intake?

 

Here are a couple pictures from the right bank. I'm not sure if GM eliminated it or relocated it. I've had that pipe with the heat shield off and there is no switch in it. Thanks for your help!

 

I just vacuum tested the NEW EGR Valve on the engine and with applying 10" of vacuum and counting down from 20 seconds it has about 2-3" of vacuum remaining at zero seconds.
Is this normal? Seems like it should have more vacuum that that?
I appreciate your help.

 

The MAP sensor is used to determine if the EGR is functioning properly.

The ECM does a diagnostic test on the EGR when in a long deceleration.
The ECM monitors the MAP voltage and opens the EGR valve and then closes
it. There should be a sudden change in the MAP voltage because of the
introduction of the exhaust gasses into the intake.

I doubt the method you used to monitor the EGR valve by Teeing into the
vacuum would work because the opening and closing of the EGR valve is to quick
to show any vacuum change in your gauge.

If you had some scanner software, you could monitor the MAP voltage vs. when
the EGR valve operates.


The Service manual describes this method to verify proper operation.
Manually apply vacuum direct to the EGR valve to open it. This causes
a pintle on the bottom of the EGR valve to be exposed to the
vacuum inside the plenum. The pintle causes the EGR valve to close when
you crank/start the engine. This is indicated by a sudden loss of vacuum on the
vacuum gauge.

You could also have clogged EGR passages. The gas flow is from the
passenger side exhaust manifold to the EGR pipe. From the pipe through some
internal intake manifold passages to the EGR valve. When the EGR valve
opens the gasses flow to an internal passage in the passenger side intake runner
next to the cylinder 6 intake runner. The gasses then flow through a internal passage
in the plenum and exit through two ports at the very front of the plenum where the
throttle body bolts to the plenum.

As for your test on how long the vacuum holds when you manually apply vacuum to the EGR valve can you try the test on your original valve?

Here's a link that describes the operation of a negative pressure EGR valve.

http://www.tomco-inc.com/Tech_Tips/ttt27.pdf

 

OK, It's getting interesting now! The original EGR valve was sticking so I applied some throttle body cleaner to free it up and a some WD40 also. I did not get any solvent on the diaphram. After this I applied 10" of vacuum and started a countdown. It slowly dropped to 3-4" after about a minute, then it held until I remove vacuum. So it makes me wonder if the original valve is ok.

Now, I checked the new valve and I now wonder if I have the correct replacement. After reviewing the Tomco Techtips article, (Thank you)the drawings in figures 3,4 and 5 look like my original. The replacement has a solid button in the bottom. I have a couple pictures of it here. This is a BWD EGR114D from O'Reilly. I went to the O'Reilly site and the BWD site and neither identified Neg or Pos B-Pressure style. Comparing this to figures 6 and 7 of the article I am still not sure.


So, I don't know what I have here and I sent a message to the tech department at BWD to help me identify this.

 

Looking at the fitment chart the BWD 114D fits 86-91 Corvettes.

It must be a negative back pressure EGR valve because a positive pressure one
wouldn't hold a vacuum unless the pintle was exposed to some pressure
which would then allow the top diaphragm to seal and allow the valve to open.

This link describes the operation of the positive pressure EGR valve.

http://www.tomco-inc.com/Tech_Tips/ttt26.pdf

The microfiche shows the original part was GM #17112240 superseded by
GM #19210674 or AC Delco 214-5535

Here's a web site showing the GM part numbers for the AC Delco EGR valve.

http://www.rmsautoparts.com/products.php?cat=5&pg=495

Since you cleaned the pintle why don't you reinstall the original EGR Valve?

 

The EGR Temp switch was eliminated for the 90 model year.