Ok guys, here's one I can't get an answer on from the locals. I have a 95 s10 Blazer with 4.3 CPI. It seems that the EGR valve may be sticking open, or, the computer is telling it to open or stay open. What sensor tells the computer to open the valve? How does it know when to open and when to close? Has anyone used one of those gaskets with a built in screen with positive results?

 

The PCM uses data from most all of the sensors to calculate when to open and close the EGR valve. There is no single sensor that controls it. If you have trouble with bits of carbon holding the valve open, the screened gaskets work well. Keep in mind that if there is any problem with the EGR system, (valve sticks open, or closed, insufficient flow, etc) the PCM will turn on the check engine light and set a DTC, (Diagnostic Trouble Code) in memory. The light will remain on until the problem is no longer present. If the light is off, and no codes are in memory, EGR is operating as it should. This holds true with all emission control sensors, devices, and associated wiring that the PCM monitors.

 

Thanks Captain Hook! As it turns out, there was carbon chunks clogging the valve and around the pintle. I let it soak in some stuff called Throttle Body and Intake Cleaner made by BG for 3 or 4 minutes. While that was soaking, I cranked the engine for about 10 seconds and some pretty big chunks came out of the manifold, then I put it back together with a screened gasket and so far, so good! Thanks for your input and sharing of knowledge!

 

Glad I could help, thanks for posting back!
The screen is designed to pulverize the carbon before it can enter the actual valve. If it accumulates on the screen, it can restrict EGR flow and the screen will need to be cleaned off. Soaking works to loosen the chunks up in the engine and starting the engine, (very loud) will blow them out, (gotta hold the throttle open a bit to keep it running). If that doesn't work, you'll need to physically clean the carbon out of the tube that goes to the exhaust manifold/head. Switching to a higher quality brand of fuel will reduce the carbon build up in the first place

 

Well, the Blazer from Hail is up and running!! Thanks for the advice, Captain Hook! I usually run the mid-grade fuel anyway, so hopefully I can keep the carbon going south. Actually, after I put the gasket on the EGR valve with the screen, it fouled up again. This time when I took the valve off, I poked around with a wire and sprayed more BG down it's throat. When I attempted to put it back together the gasket separated into two halves with the screen falling out. I had some similar stainless wire (left over from making bilge pump boxes) so I cut out a piece big enough to cover both holes and put it together with red high temp rtv silicone. It ran like a dream today, maybe a nightmare tomorrow, but today it ran really smooth and strong. I may even give it a more favorable nick name! Thanks again!