EGR & vacuum question
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Joined: Dec 2000
Posts: 116
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From: Jacksonville, FL
EGR & vacuum question
Should the EGR valve hold a vacuum when I attach a hand-pump directly to it?
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86 IROC TPI 305
700-R4 with Trans-go shift kit
K&N Air filters
Dyno-Max cat-back
Summit tranny cooler
CEI throttle enhancer chip
Gutted MAF
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Joe,
I'll try to cover both of your questions at once.
The handheld vacuum pump is used to apply vacuum to a single component at a time, not to evacuate the entire intake manifold to test for leaks. Since there can be any number of valves open, and the throttle plates don't seal completely, and the PCV valve is suppoed to bleed some vacuum contantly, you would never be able to achieve any vacuum in the intake using a handheld pump.
Your EGR valve is a good example of how to use the pump. The FPR is another example. The FPR should haold vacuum after you pump the air out. However, an EGR valve may or may not hold vacuum.
Since you have a TPI, you also have an EGR valve with a pilot presure valve. Some of these are a positive backpressure type, and some are a negative backpressure type. In either case, the pilot pressure valve requires some pressure differential in the exhaust ports and the EGR passages in the intake manifold. A handheld vacuum pump is not a good way to diagnose one of these valves unless you have the fixtures to apply a pressure differential across the ports in the base at the same time.
But don't be too concerned. If the EGR system is not working, you'll generate an error code the first time you do any cruising at highway speeds for a couple of minutes. The one thing you can check for is carbon buildup in the manifold ports and EGR valve base, but it isn't a lot of fun to access the valve unless the plenum is already removed.
------------------
Later,
Vader
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"Click - Click - BOOM!"
Adobe Acrobat Reader
I'll try to cover both of your questions at once.
The handheld vacuum pump is used to apply vacuum to a single component at a time, not to evacuate the entire intake manifold to test for leaks. Since there can be any number of valves open, and the throttle plates don't seal completely, and the PCV valve is suppoed to bleed some vacuum contantly, you would never be able to achieve any vacuum in the intake using a handheld pump.
Your EGR valve is a good example of how to use the pump. The FPR is another example. The FPR should haold vacuum after you pump the air out. However, an EGR valve may or may not hold vacuum.
Since you have a TPI, you also have an EGR valve with a pilot presure valve. Some of these are a positive backpressure type, and some are a negative backpressure type. In either case, the pilot pressure valve requires some pressure differential in the exhaust ports and the EGR passages in the intake manifold. A handheld vacuum pump is not a good way to diagnose one of these valves unless you have the fixtures to apply a pressure differential across the ports in the base at the same time.
But don't be too concerned. If the EGR system is not working, you'll generate an error code the first time you do any cruising at highway speeds for a couple of minutes. The one thing you can check for is carbon buildup in the manifold ports and EGR valve base, but it isn't a lot of fun to access the valve unless the plenum is already removed.
------------------
Later,
Vader
------------------
"Click - Click - BOOM!"
Adobe Acrobat Reader
Thread Starter
Member
Joined: Dec 2000
Posts: 116
Likes: 0
From: Jacksonville, FL
Guess what... I currently have the plenum removed. That's why I want to nail this now. I need to put the plenum back on tonight so i can drive to work tomorrow...
So go ahead and tell me what you would do if you had the plenum removed.
Joe
------------------
86 IROC TPI 305
700-R4 with Trans-go shift kit
K&N Air filters
Dyno-Max cat-back
Summit tranny cooler
CEI throttle enhancer chip
Gutted MAF
So go ahead and tell me what you would do if you had the plenum removed.
Joe
------------------
86 IROC TPI 305
700-R4 with Trans-go shift kit
K&N Air filters
Dyno-Max cat-back
Summit tranny cooler
CEI throttle enhancer chip
Gutted MAF
Moderator
Joined: Jan 2000
Posts: 19,679
Likes: 316
Joe,
IF I had the plenum removed...
...I'd pull off the EGR valve, clean the EGR ports in the intake with some spray carb cleaner and a small stiff brush (a steel solder flux brush works well), then blow them out with compressed air or suck out the debris with a shop vac.
Then I'd clean the base of the EGR with the brush. Then vacuum or blow out the passages in the EGR valve.
CAUTION: Don't use and solvents or cleaners on the EGR valve itself, since the rubber pilot valve we discussed earlier is not impervious to solvent. The pilot valve seal is made to operate at high temperatures, and because of the rubber compound used, it can dissolve in solvent or cleaners.
Once the valve is clean, observe the valve pintle through the bottom port. Manually actuate the valve diaphragm and make sure the valve pintle moves with it. Check to be sure the pintle seats fully and seals completely in the valve base. If there is any erosion or the valve doesn't seal completely, start calling around for a new valve, ASAP.
If you have a DMM, check the operation of the temperature sensor in the base of the EGR valve:
Check the resistance of the sensor at a given temperature. Compare your readings to the table:
If everything checks out O.K., start reassembling. Make sure you apply anti seize compound to all the fasteners. Before you get the plenum installed, loosen the distributor hold down bolt carefully so you don't move the distributor and alter the timing. Remove the bolt and apply anti seize to this bolt, then reinstall it. Access to this bolt is very difficult when the system is assembled and you'll be really frustrated it the bolt is seized - now's your chance to fix it.
If everything has gone well to this point and you have a couple of hours left before sunrise, consider a quick plenum port cleanup behind the throttle body if you haven't already done so. That is the biggest single restriction in the system, and is worth opening up. If you decide to do this, check this file:
Plenum Porting.pdf
When you're finished, get the DMM out again and set the TPS sensor position, reset the throttle minimum air position, then recheck the TPS voltage.
Let me know how it goes.
------------------
Later,
Vader
------------------
"Click - Click - BOOM!"
Adobe Acrobat Reader
IF I had the plenum removed...
...I'd pull off the EGR valve, clean the EGR ports in the intake with some spray carb cleaner and a small stiff brush (a steel solder flux brush works well), then blow them out with compressed air or suck out the debris with a shop vac.
Then I'd clean the base of the EGR with the brush. Then vacuum or blow out the passages in the EGR valve.
CAUTION: Don't use and solvents or cleaners on the EGR valve itself, since the rubber pilot valve we discussed earlier is not impervious to solvent. The pilot valve seal is made to operate at high temperatures, and because of the rubber compound used, it can dissolve in solvent or cleaners.
Once the valve is clean, observe the valve pintle through the bottom port. Manually actuate the valve diaphragm and make sure the valve pintle moves with it. Check to be sure the pintle seats fully and seals completely in the valve base. If there is any erosion or the valve doesn't seal completely, start calling around for a new valve, ASAP.
If you have a DMM, check the operation of the temperature sensor in the base of the EGR valve:
Check the resistance of the sensor at a given temperature. Compare your readings to the table:
If everything checks out O.K., start reassembling. Make sure you apply anti seize compound to all the fasteners. Before you get the plenum installed, loosen the distributor hold down bolt carefully so you don't move the distributor and alter the timing. Remove the bolt and apply anti seize to this bolt, then reinstall it. Access to this bolt is very difficult when the system is assembled and you'll be really frustrated it the bolt is seized - now's your chance to fix it.
If everything has gone well to this point and you have a couple of hours left before sunrise, consider a quick plenum port cleanup behind the throttle body if you haven't already done so. That is the biggest single restriction in the system, and is worth opening up. If you decide to do this, check this file:
Plenum Porting.pdf
When you're finished, get the DMM out again and set the TPS sensor position, reset the throttle minimum air position, then recheck the TPS voltage.
Let me know how it goes.
------------------
Later,
Vader
------------------
"Click - Click - BOOM!"
Adobe Acrobat Reader
Last edited by Vader; Mar 21, 2002 at 11:30 AM.
Thread Starter
Member
Joined: Dec 2000
Posts: 116
Likes: 0
From: Jacksonville, FL
Vader,
As usual, you go above and beyond the call of duty!
I unloaded 2 1/2 cans of carb cleaner on the plenum. That thing was totally coked. I dont know how the air temp sensor could get a reading...
As for the EGR valve, I couldnt get the bolts off because the space was too tight. I couldnt fit a small wrench in there, and I didnt want to strip the bolt head off. The thing is, I do occassionally get the code 32. I imagine that's from the EGR passageways also being coked up as well. Next time I'll get a stubby wrench...
Anyways, the problem seems to have gotten better. I figure that air was leaking into the manifold somewhere, and disassembling/reassembing everything on top of the motor fixed whatever the problem was. I also replaced the upper runner gaskets and throttle body gasket.
Once again, your response to my query was outstanding. It was truly appreciated. And the pdf article -- awesome. I wish I had the tools to do it.
Joe
------------------
86 IROC TPI 305
700-R4 with Trans-go shift kit
K&N Air filters
Dyno-Max cat-back
Summit tranny cooler
CEI throttle enhancer chip
Gutted MAF
As usual, you go above and beyond the call of duty!
I unloaded 2 1/2 cans of carb cleaner on the plenum. That thing was totally coked. I dont know how the air temp sensor could get a reading...
As for the EGR valve, I couldnt get the bolts off because the space was too tight. I couldnt fit a small wrench in there, and I didnt want to strip the bolt head off. The thing is, I do occassionally get the code 32. I imagine that's from the EGR passageways also being coked up as well. Next time I'll get a stubby wrench...
Anyways, the problem seems to have gotten better. I figure that air was leaking into the manifold somewhere, and disassembling/reassembing everything on top of the motor fixed whatever the problem was. I also replaced the upper runner gaskets and throttle body gasket.
Once again, your response to my query was outstanding. It was truly appreciated. And the pdf article -- awesome. I wish I had the tools to do it.
Joe
------------------
86 IROC TPI 305
700-R4 with Trans-go shift kit
K&N Air filters
Dyno-Max cat-back
Summit tranny cooler
CEI throttle enhancer chip
Gutted MAF
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