Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Blowing EGRs?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BadDog, Jan 4, 2002.

  1. BadDog

    BadDog SOL Staff Member Super Moderator Author

    Joined:
    Feb 24, 2001
    Posts:
    7,777
    Likes Received:
    11
    Location:
    Phoenix, AZ
    Well, I've had my EGR blocked off for the last couple of weeks and several people here have convinced me that I need to fix it. So, off to the parts house and I've got a brand spanking new EGR valve for $60. Just put it on today. Cranked and ran fine, then, about the time it warmed up well enough to throw the solenoid, I get a major miss and stumble that won't stop. Really hard to crank and won't stay running if it does. Humph!

    So, I check for whatever. Loose wired, tubes, etc. Everything looks fine. The EGR however will not hold vacuum! Looks like the diaphragm is blown and it is stuck open!

    Now, here is my question. What could cause this? Man I hope I don't have a cracked head. The old diaphragm will hold vacuum so I know it didn't blow the diaphragm, it just causes a stumble when it opens. I guess my SOL luck struck again and I got a bad valve..?

    If I don't hear some words of wisdom soon, I'll just pull this off and go exchange it to try again...

    Russ

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,979
    Likes Received:
    189
    Location:
    Roy WA
    I've heard some things about aftermarket EGR's vs GM pieces, but I'm betting the price difference ain't worth it. Try another one, if it blows, I think I'd be looking for another cause...should be able to hold up to full manifold vacuum without blowing, thats for sure! Unfortunately, from your previous description, sounds like its a big hassle to swap.

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>www.dorianyeager.com/index2.html</a>
    Why insist on counting when the ring gear has the tooth counts stamped in?
     
  3. BadDog

    BadDog SOL Staff Member Super Moderator Author

    Joined:
    Feb 24, 2001
    Posts:
    7,777
    Likes Received:
    11
    Location:
    Phoenix, AZ
    Funny thing is, I can't find anything wrong with my original EGR. It holds vacume, moves full range, seals off the valve when no vacume. I don't get it. All I know is that when I plugged the line going to the EGR (at the point where it goes on the EGR so no, it's not a leaking line) the thing runs perfect. Anyway, I've got another I'm putting on now. I'll update in an hour or so...

    Russ

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  4. solowookie

    solowookie 1/2 ton status

    Joined:
    Mar 31, 2001
    Posts:
    3,880
    Likes Received:
    0
    Location:
    Wyoming
    it is a sign from the chev that it doesn't want the EGR working... [​IMG]

    <font color=blue> Jeff - may the force be with you</font color=blue>
    <a target="_blank" href=http://coloradok5.com/gallery/Jeffs-Stuff>link to k5's</a>
     
  5. BadDog

    BadDog SOL Staff Member Super Moderator Author

    Joined:
    Feb 24, 2001
    Posts:
    7,777
    Likes Received:
    11
    Location:
    Phoenix, AZ
    LOL! I think you may be right. Or maybe it just wants "genuine GM". I just blew the second EGR! So, I put the original back on (still holds vacuum fine) and had the same (original) problem. Engine stumbles when it warms up.

    Now, I have no clue about why the EGRs are blowing. Vacuum is not that high, and the GM EGR is holding up in there just fine. However, I've done some more thinking about the stumble problem. It seems like the EGR solenoid is opening at too low an RPM, even at idle. With the line plugged, it runs like a champ. I can simulate the problem exactly by gently sucking on the vacuum line when the engine is at low rpm. If I still owned a vacuum gauge I'm sure it would show the EGR solenoid opening even at 600-1000 rpms.

    So, my current hypothesis is that my lack of a VSS is confusing the ECM into opening the EGR at the wrong times. Or maybe my TPS is not working right. I found out today that the plug (on the harness side, not the sensor) is broken up inside, but the conductors seem to be making up fine. I remember someone saying that the VSS could be eliminated by grounding pin 10 (??) to make it think that you were always in park. Apparently, some aftermarket harnesses do this to eliminate the VSS requirement. Anyway, what do you guys think? Am I on the right track? Or, did I breathe too much CO today?

    Russ

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  6. BadDog

    BadDog SOL Staff Member Super Moderator Author

    Joined:
    Feb 24, 2001
    Posts:
    7,777
    Likes Received:
    11
    Location:
    Phoenix, AZ
    The first one I blew was from Checker. I returned it and they didn't have another so I got my money back and went down the street to NAPA. Exactly the same EGR in a different box for $10 more. Same instructions, same washers, same EGR valve, same everything. Anyway, since the second blew, I'll just return it to NAPA and I won't have to worry about "if you blew 2 of them it must be something wrong with your engine so you'll have to eat it"...

    Russ

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  7. Twiz

    Twiz 1/2 ton status

    Joined:
    Mar 8, 2001
    Posts:
    3,729
    Likes Received:
    0
    Location:
    Clearfield Ut.
    B.D. give me some details, I need to know what you are running. Does the valve have a N or a P stamped on it?

    I'm not a drivability guy, but I'll give it a shot. (*read*, have a '92 S/M, in my lap)

    Details man, details.

    <font color=blue>Wow Factor
    A SBC at 6000 RPM, Piston speed of 60 MPH.
    3- The intake charge reaches a speed 4 X greater than the piston.
    Thats 240 MPH.
     
  8. solowookie

    solowookie 1/2 ton status

    Joined:
    Mar 31, 2001
    Posts:
    3,880
    Likes Received:
    0
    Location:
    Wyoming
    ok this is a shot in the dark cuz I don't know anything about this compared to everybody else here, but there goes anyway; what about trying different sized washers???

    <font color=blue> Jeff - may the force be with you</font color=blue>
    <a target="_blank" href=http://coloradok5.com/gallery/Jeffs-Stuff>link to k5's</a>
     
  9. BadDog

    BadDog SOL Staff Member Super Moderator Author

    Joined:
    Feb 24, 2001
    Posts:
    7,777
    Likes Received:
    11
    Location:
    Phoenix, AZ
    Ok, had to go out and get it. Brrrrr...

    DCT 17087196
    217 12N

    That's all there is. Thanks for the help.

    Russ

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  10. BadDog

    BadDog SOL Staff Member Super Moderator Author

    Joined:
    Feb 24, 2001
    Posts:
    7,777
    Likes Received:
    11
    Location:
    Phoenix, AZ
    Trying different washers would be difficult since it blows immediately, and they are "staked" in there with a punch. I used the one recommended for my EGR number.

    Russ

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  11. Twiz

    Twiz 1/2 ton status

    Joined:
    Mar 8, 2001
    Posts:
    3,729
    Likes Received:
    0
    Location:
    Clearfield Ut.
    Yeah, I figured thats what you did. Yeah, right- "brrr" in Az.?

    -K- see if this helps out at all

    Negative Backpressure EGR valve
    The neg. b.p. EGR valve has the bleed valve spring below the diaphram, and the valve varies the amount of exhaust gas flow into the manifold depending on manifold vacume and variations in exhaust backpressure. (basic opperation of most vacume controled EGRs)

    The diaphram on this valve has an internal air bleed hole which is held closed by a small spring when there is no exhaust pressure. (Hmm, think the open pipes might have something to do with this?)

    Engine vacume opens the EGR valve against the pressure of a large spring. When manifod vacume is combined with negative exhaust pressure backpressure, the vacume bleed hole opens and the EGR valve closes.

    Solenoid With Negative Backpressure EGR (sounds like this is the animal you have)
    To regulate EGR flow an ECM controlled solenoid is used in the vacume line. This is normally closed colenid vacume valve which is open when the ECM completes the ground. (got it hooked up right?) The ECM will engergize solenoid when the engine is warm and above idle. TRhere is little EGR flow at WOT due to lack of throttle.
    -
    I did a quick scan, didn't see anything that "jumped out" at me.
    Maybe this will help. If not I could relay the Sys. check and we can go from there.

    <font color=blue>Wow Factor
    A SBC at 6000 RPM, Piston speed of 60 MPH.
    3- The intake charge reaches a speed 4 X greater than the piston.
    Thats 240 MPH.
     
  12. BadDog

    BadDog SOL Staff Member Super Moderator Author

    Joined:
    Feb 24, 2001
    Posts:
    7,777
    Likes Received:
    11
    Location:
    Phoenix, AZ
    Hey, Brrrr is relative. [​IMG]

    I'm not sure exactly what to make of this yet. I do have somewhat open pipes. 2 into 1 3" with a 30"x2.5" glass pack where the cat used to be and 24" of 2.5" after that. I used the 2.5 to give it some back pressure. Maybe there is not enough? If the valve stays closed, I guess the EGR stays wide open under vacuum? Still, it seems that when this thing start killing the engine, the vacuum would drop, and the valve would close. The plunger/diaphragm does seem a little sluggish and slow, although it doesn't feel rough or sticky.

    The second part about the solenoid opening when warm and above idle is EXACTLY what is going on when it starts to stumble. Eventually, if you can keep it running, it will settle down. I'm guessing the EGR is closing when it settles down.

    Thanks but, I'm still not sure what to make of it. I'm going to try to meet up with Doug (AZBlazer) this weekend so maybe I can look at his manuals. I hate for you to go to the trouble of try to relay all that stuff. Thanks anyway...

    Russ

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  13. Twiz

    Twiz 1/2 ton status

    Joined:
    Mar 8, 2001
    Posts:
    3,729
    Likes Received:
    0
    Location:
    Clearfield Ut.
    O.K., first hand is always better than tring to diag something of the net. Hope you guys get it figured out!

    Let me know if there is something I can look up for you.
    The ECM uses the TPS, MAP, and ECT to base EGR opperation.

    Later.

    <font color=blue>Wow Factor
    A SBC at 6000 RPM, Piston speed of 60 MPH.
    3- The intake charge reaches a speed 4 X greater than the piston.
    Thats 240 MPH.
     
  14. 84_Chevy_K10

    84_Chevy_K10 Banned

    Joined:
    May 30, 2001
    Posts:
    17,669
    Likes Received:
    0
    Location:
    IL, USA
    Just ditch the EGR all together. It's useless.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  15. BadDog

    BadDog SOL Staff Member Super Moderator Author

    Joined:
    Feb 24, 2001
    Posts:
    7,777
    Likes Received:
    11
    Location:
    Phoenix, AZ
    It's not useless if you want to pass emissions. Not that it matters for me. I've also recently learned that it causes trouble for the ECM if it's not functional AND the engine itself runs *better* when it is working properly.

    Russ

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  16. BadDog

    BadDog SOL Staff Member Super Moderator Author

    Joined:
    Feb 24, 2001
    Posts:
    7,777
    Likes Received:
    11
    Location:
    Phoenix, AZ
    You know, it occurs to me that if that bleed valve were stuck *closed*, it could cause the EGR to open (or stay open) when it should close. That might be my problem.

    Russ

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  17. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    Unplug the wires that go to the control solenoid and see if the problem is still there. There shouldn't be any vacuum to the EGR line until the computer tells the solenoid to turn on. The computer will send pulses to the solenoid, similar to what it does for the injectors. By adjusting the pulse width, it controls how far the EGR valve opens.

    Anyway, if the EGR valve still opens when the power to the solenoid is disconnected, then the solenoid is either bad or has something stuck inside of it.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
    It's a great day to be alive...
     
  18. Twiz

    Twiz 1/2 ton status

    Joined:
    Mar 8, 2001
    Posts:
    3,729
    Likes Received:
    0
    Location:
    Clearfield Ut.
    Yeah, B.D. if the bleed is cloged it would keep the valve open. I know the drivability guys dal with carbon cloging something on the EGRs, I would assume thats it. (Wish I was paying attation-)

    EGR sys check, negative backpressure EGR *identified with a N stamped on it* and without 4L80-E trans

    No codes 23 or 32 set (diagnose codes first)

    1- Applie vacume to manifold side of solenoid, does it hold vacume? - No, replace solenoid (yes, continue diag)
    2-Turn ign to "run" engine off, does vacume drop? - Yes, ckt 435 short to ground or faulty ECM (no, continue diag)
    3- Ground diagnostic "test" terminal, does vacume drop? - No, possible wiering or solenoid problem (yes, continue diag)
    4- Remove gronded diagnostic test, Ign "off", connect vacume pump to EGR side of vacume harness, check movement of EGR diaphragm while appliing vacume, diaphram should move freely and hold vacume for 20 sec. Does it? - No, check for restriction in vacume line, if its O.K., replace the EGR valve. (if yes continue diag.)
    5- Applie vacume to EGR valve, start engine and immediatly check vacume and valve postion, valve is good if it moves to the seated postion and vacume dropped while starting engine, does the val;ve opperat normaly? - yes, check park/neutarl switch. - no, check for passages cloged on the EGR valve, replace valve.

    Test steps description, (This is what each step is checking)
    1- checks for solenoid stuck open
    2- checks for solenoid allways energized
    3- grounding the test terminal should engergize the solenoid and vacume should drop
    4- negative backpressure valve should hold vacume with engine off
    5- when engine is started, exhaust backpressure should cause the vacume to bleed off and valve should fully close.

    <font color=blue>Wow Factor
    A SBC at 6000 RPM, Piston speed of 60 MPH.
    3- The intake charge reaches a speed 4 X greater than the piston.
    Thats 240 MPH.
     
  19. BadDog

    BadDog SOL Staff Member Super Moderator Author

    Joined:
    Feb 24, 2001
    Posts:
    7,777
    Likes Received:
    11
    Location:
    Phoenix, AZ
    I've checked each of those things in one way or another. The solenoid is cycling on and off. It is closed when cold, and when warm it opens. The EGR port is clear. The valve cycles fully and holds vacuum. I don't see any carbon buildup that prevents the actual valve from seating/sealing (plus it runs fine until the solenoid hits it with vacuum after warm up).

    There seems to be no way to check the "exhaust pressure bleed valve".

    I think I'm at a dead end without a scanner. After some more thought and reading, I think that there are several possibilities. The EGR bleed off valve is stuck closed preventing it from cycling based on exhaust pressure. The EGR is sticky and not responding quickly enough to inputs causing the ECM to get confused. ECM is confused by one or more inputs (possibly MAP or TPS based on reading) and is not modulating the EGR correctly once it goes "closed loop".

    Also wondering if those two EGR valves were actually bad. I wasn't smart enough to check them before install (even on the second one!!! Duh!!! [​IMG]). Anyway, if the bleed valve is open on them then that would explain why they won't hold vacuum. Or maybe something on my engine hammered them after I installed them and damaged/stuck the bleed valves? The 2-outa-2 "bad" (or damaged) new EGRs, but the original seems to have no problem surviving (or at least holding vacuum), have got me stumped. Every way I can think of to test the original EGR shows it "good". My head hurts. I need a scanner...

    Russ

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  20. Twiz

    Twiz 1/2 ton status

    Joined:
    Mar 8, 2001
    Posts:
    3,729
    Likes Received:
    0
    Location:
    Clearfield Ut.
    Results of Incorect opperation of the EGR-
    - Stop the engine after cold start
    - Engine stalls at idle after deceleration
    - Vehicle surges during cruise
    - Rough idle
    Too little or no EGR opperation will
    - Possibly induse spark knock (detonation)
    - Possibly cause engine over heating

    The EGR valve recirculats measured amounts of exhaust gas back into the intake during a part throttle cruise (light engine load, and above idle). The exhaust gas that is recurculated into the engine, cools the combustion temps and reduses NOX emmissions. It should have (if opperating properly) no effect on engine performance, since its opperation is at part-throttle and light load. (now this much, I actualy knew, guess I was paying attation at some-point.[​IMG])

    <font color=blue>Wow Factor
    A SBC at 6000 RPM, Piston speed of 60 MPH.
    3- The intake charge reaches a speed 4 X greater than the piston.
    Thats 240 MPH.
     

Share This Page