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GM Mystery - EGR 95-99


Michael Savage

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I've noticed my mothers 98 Lumina shares the same Digital EGR as my 95 which was supposed to be the last year. We'll I noticed when I picked up one for my car and it came off a 97 Pontiac. I would like to here from people who have seen this before. Listings for 96-99 only show the Linier EGR. The OBD2 system on my mothers car she bought new at the GM dealership in 98/99 shows all the codes for each solenoid for the digital EGR and functions proper and passed emissions.

I'm wondering why some of these cars have the Digital on them but it isn't listed. Send pictures or car year make and model I'm wanting to make a list to see if it's just certain cars or if it's every model.

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I'm unclear what digital vs linear is? There are only 2 types I've seen on a GM, and of those only 1 has a feedback of any sort in the form of a pintle position sensor. I've never noticed anything but the 5 wire (Pintle Position Sensor) type on a W-Body. It's 2 wires to control the solenoid, and 5V, Low Reference, Signal for the other 3. I'm using the signal input from the Fuel pressure sensor on mine so I know it's a 0-5V sweep input.

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digital = 3(or 2, on the 4 cylinder cars that used them) discrete solenoids, used in combination to make 8 different EGR flowrates. no flow testing other than delta-MAP during certain coastdown events.

linear = starting in 94ish, GM made a linear response EGR valve(has a position sensor)

 

before those, negative backpressure EGR, positive backpressure EGR, EVRV EGR..... probably more, some were more sophisticated than others, but they all seemed to be failure-prone.

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eseze2yr.jpg

This EGR is Digital, it was supposed to be phased out in 95 but I've noticed it poping up on 96-99 cars with the 3100 engine. Part listings don't show it as an option either.

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I've also heard they tend to be failure prone. I already have a spare for my '95 LQ1, just in case.

digital = 3(or 2, on the 4 cylinder cars that used them) discrete solenoids, used in combination to make 8 different EGR flowrates. no flow testing other than delta-MAP during certain coastdown events.

linear = starting in 94ish, GM made a linear response EGR valve(has a position sensor)

 

before those, negative backpressure EGR, positive backpressure EGR, EVRV EGR..... probably more, some were more sophisticated than others, but they all seemed to be failure-prone.

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Yeah that's my spare, if you take the 3 torque bolts off the metal plate between the 3 black towers, you can take apart the entire EGR. They're not fully bad. The solenoids get coated in carbon. Remove all 3 solenoids individually and soak them in carb Cleaner for an hour them spray cleaner on them push on the springs and spray out the solenoid sockets then reinstall together and it should be fine. Carful the bolts are prone to stripping.

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