Vacuum leak from EGR Solenoid?

Drewster

Wish I Had A Clone. AKA Andrew Youlio
Joined
May 31, 2001
I tested the EGR solenoid for a vacuum leak and found out that it was completely open. wont hold vacuum at all! This was with the car off,key on, and engine running. no change.
I dont know if that is the way its supposed to be or what. Im not getting a code or anything.

anyone know off hand?
 
egr solenoid

Hi,
Your solenoid must have been venting, or you would have a lousy, or no idle.I think they are closed when at rest. Do you have a vacuum signal to the valve at idle? Some GM egr valves are negative backpressure transduced, so they won't open when there isn't a backpressure signal from the exhaust. I don't think our turbo cars are in this category.
Try this: Ground a to b on the ALDL, key on engine off.Attach a hand vacuum pump to the source on the control unit, pump it up to 10", if possible.Disconnect the jumper on the ALDL, and observe the gauge on the pump. Any changes?
I don't have access to the flow chart for egr problems, many different configurations were used by GM, and I'm not sure what our cars use.Being away from my manual info,not certain here.I would guess that this system was design to fail without causing undue driveability issues. By the way, a diagnostic switch in incorporated into the control unit, and no EGR will turn on a light and set a code.
I remember when I first got my car going, I wanted to check the boost solenoid.A WOT snap with the key on, engine off would cycle the solenoid, just like the EECIV Fords do.I would expect that all outputs are cycled when doing this.Try it, then you won't have to mess with disconnecting and reconnecting the ALDL jumper. I can get you more specific info if needed, just not today. Let me know, drop me an email if you need it.
 
Yesterday I pulled my EGR valve off, scraped all the gasket off, flattened the surface with a sharpening stone, and reassmbled it without a gsket...just a little copper RTV. I put a vacuum plug on the barb to make it a little harder for the shaft to move up when exhaust backpressure gets high and plugged the vacuum line. I basically disabled it cause the extender chip doesnt use EGR anyway. I think I may have had a little crosstalk going on between the 2 ports on the intake, because my EGR solenoid worked fine, but whenever my engine got hot it would idle terribly, and now it idles great. My cruise BLMs went up about 10 points though, which makes me wonder...All I know is that it idles much much better than before. Used to idle like a 330 degree cammed 4 cylinder. I fixed all the vacuum leaks which helped alot, but i had this lingering problem that wouldnt go away.
 
ill have to try the solenoid check durring key cycle.
i did find 2 decent vac leaks. one on the vac line to the egr and one on the MAP sensor line. car revs much quicker now and more accurate boost readings.
fyi pulling vac on the egr valve will stall the car at idle.
 
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I have been searching and searching for vacuum leaks on my 87 GN. I fabricated a couple adapters to bolt onto the front of the throttle body and one to bolt straight onto the intake plenum. I am able to pressurize the system with low psi compressed air. Then I just spray soapy water around searching for leaks. When I did the test through the throttle body I found a few vacuum leaks on the vacuum block but the biggest leak was coming from around the throttle shaft, the tps side and the linkage side. I know that there would be a little leakage there but it seemed to me to be way to much. By to much I mean when I spray the soapy water on it shoots right back off in a stream. And I only use 10 to 20 psi of air. I did another test after I took the throttle body off and put pressure straight to the intake plenum. And there seems to be a fairly serious leak coming from the egr. Not the solenoid, not where it bolts onto the intake, but from around the diaphragm itself. Is it normal for it to be like that or is that a problem? I would very much appreciate any hints, tips and information on these issues and how to make proper repairs. Especially this egr thing. Should I replace the the unit, take it off and make a block off plate? What's the best way to go about this. I'm in alberta canada by the way, and I don't think there is an emissions test here. Don't quote me on that though. Here are the two adapters I made.
 
View attachment 260786 View attachment 260787 View attachment 260786 View attachment 260787 I have been searching and searching for vacuum leaks on my 87 GN. I fabricated a couple adapters to bolt onto the front of the throttle body and one to bolt straight onto the intake plenum. I am able to pressurize the system with low psi compressed air. Then I just spray soapy water around searching for leaks. When I did the test through the throttle body I found a few vacuum leaks on the vacuum block but the biggest leak was coming from around the throttle shaft, the tps side and the linkage side. I know that there would be a little leakage there but it seemed to me to be way to much. By to much I mean when I spray the soapy water on it shoots right back off in a stream. And I only use 10 to 20 psi of air. I did another test after I took the throttle body off and put pressure straight to the intake plenum. And there seems to be a fairly serious leak coming from the egr. Not the solenoid, not where it bolts onto the intake, but from around the diaphragm itself. Is it normal for it to be like that or is that a problem? I would very much appreciate any hints, tips and information on these issues and how to make proper repairs. Especially this egr thing. Should I replace the the unit, take it off and make a block off plate? What's the best way to go about this. I'm in alberta canada by the way, and I don't think there is an emissions test here. Don't quote me on that though. Here are the two adapters I made.


Did you pick those valve stems up at a local tire shop? I need to one or a check valve so I can apply 10psi to RA volt booster and keep my voltage at 15v+ while I'm trying to figure out an issue. I would use the check valve from canister vent, but at nearly 30 years old it no work anymore.
 
Did you pick those valve stems up at a local tire shop? I need to one or a check valve so I can apply 10psi to RA volt booster and keep my voltage at 15v+ while I'm trying to figure out an issue. I would use the check valve from canister vent, but at nearly 30 years old it no work anymore.
Ya. I just grabbed a four pack of valve stems at princess auto. They were like 3 bucks or something. I'm sure any auto parts store or like you said any tire shop would probably have them.
 
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