EGR Valves...etc...

[gmrulz4u]

Is it true that the EGR Valve is supposed to remain CLOSED until the engine is at "Operating Temperature"?

 

Also, does the EGR Valve send the signal to the ECM, or does the ECM send one to the Valve??

 

One more thing, what exactly IS "Operating Temperature" with our engines?

 

THANKS:)

[davidarel]

I am assuming you are talking about a "digital" EGR valve like the ones used on the 3.4's and such. These valves are bi-directional, meaning that the computer sends a signal to open or closed and according to the resistance readings, the computer knows what position the plunger is at. These valves are always adjusted by the computer as the driving gets more aggressive or passive, i.e. throttle position. The earlier egr valves were nothing more than vacuum solenoids triggered by a signal from the computer at operating temperature signal from the coolant sensor and various other reading throughout the motor.

 

As far as "operating temperature" goes, this is the value that the engine sees most of its driving in. Usually it is anywhere from 195 to 215 degrees. A good way to tell is to look at your temp gauge and notice where it is while you are driving on the highway. This will give you a very good idea of what your operating range is. Not all cars are the same so yours will be different than a truck for example. Keep in mind though, the gauge gets its signal from a different sensor than the computer does. The gauge is nothing more than a resistance value when the sensor is grounding to the block. You can tell this sensor by a dark green wire connected to the head or block on most GM cars. The computer on the other hand uses a black and yellow color wires connected to the sensor located in the same approximate location. This sensor actually sends a "signal" (yet another resistance value) back to the computer. This sensor is critical to the operation of the motor. The computer uses the coolant temp. to determine when the motor is in operating range which will signal the O2 sensor (on 1-wire O2's), determing fuel timing, torque converter lockup in some cases, spark timing, and several other engine parameters. If this didn't answer your questions feel free to post a follow up and i can clarify.

[gmrulz4u]

Thanks! But I am actually referring to the EGR valves that were used up until 1990/91 in our 2.8(all) and 3.1(some) engines. It's not the digital kind, but rather the vacuum controlled kind.

 

The reason I asked is because I find, via my AutoXray OBD Scanner(live Data), that my EGR valve starts opening when the engine is only at like 80-90 degrees Farenheit, which I'm not sure if it's low or not?

 

Also, my car goes into "Closed Loop" usually right around 100 degrees Farenheit...I think this is OK? My O2 Sensor changes rapidly and is only 1 year old...

[Robby1870]

Im pretty sure the O2 should change all the time. I was with my friend while he as dataloggin his car, and the O2 was constantly changing.

 

Robby

[gmrulz4u]

Im pretty sure the O2 should change all the time. I was with my friend while he as dataloggin his car, and the O2 was constantly changing."

 

Yeah I know:) That's why I was saying that, to emphasize the fact that I know my O2 Sensor is working perfectly:)!!

[Robby1870]

oh, I thought you were commenting on that is was only 1 year old and already messing up. My bad :oops: :oops:

 

Robby

[davidarel]

The O2 sensor is doing its job if it keeps fluctuating up and down. If i remember correctly, the readings should be somwhere in the 800 to 900 range. I use an actron scanner (real time) on mine so that is where i get my info. Your egr valve sounds like it is opening a little too soon. But, I could be wrong. Are you using a 4 wire O2 or a 1 wire? If it is a 4 wire then going into closed loop thast soon sounds right, but if it is a 1 wire the exhaust has to heat up the sensor to the designated range before the computer goes into closed loop. The egr on the other hand should be connected to to a switch via a vaccuum hose. The electrical connection is nothing more hthat a solenoie with a few other vacuum hoses connected to it. if this switch is going out, i don't think it will set a code unless the computer doesn't see any signal at all. If i remember correctly, the name of the "switch" is the egr solenoid. I would use an ac deco unit if you are going to replace it. The aftermarket brands just don't seem to last as long or work in exactly the same way. I fyou can get a part number off the piece, go to http://www.gmpartsdirect.com for the part. They sell gm parts at a fraction of what the dealer would charge.