No vacuum to EGR valve ... 4.9 engine
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HT4100 4.1, 4.5, 4.9 Discussion, No vacuum to EGR valve ... 4.9 engine in Cadillac Engine Technical Discussion; Well, I took my 1992 Seville, 4.9 engine, down for a smog check and it passed with flying colors, except ...
  1. #1
    runforrest1 is offline Cadillac Owners Member
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    No vacuum to EGR valve ... 4.9 engine

    Well, I took my 1992 Seville, 4.9 engine, down for a smog check and it passed with flying colors, except for the NOx. It's an EGR problem for sure. I checked for vacuum from the throttle body to the solenoid and it's getting a full 20 inches. I checked the solenoid for vacuum flow with and without the wire connector. Without being connected I get vacuum flow and with it connected I get nothing, even with engine all warmed up and running it well over 2,000 RPMs. From what I've read, the computer varies the opening and closing by controlling the ground to it. Shouldn't I be getting some open time with vacuum flow or does the engine have to be under an actual load and above 2,000 RPMs?

    As far as the EGR valve itself, I tried to test it by putting my vacuum pump on it while running at way high RPMs and it doesn't hold any. From what I've read, it is a positive back pressure type and needs high RPMs to force the valve up before the vacuum can hold. I thought that the low restriction type cat that I put on it last summer (Magnaflow) might be a problem so stuffed rags into the exhaust pipes. That made no difference. I will probably pull the EGR valve today and replace it if need be, but if it isn't getting any vacuum it's not going to solve the problem.

    It was cold and dark last night when I was out in the driveway messing with it. I started to pull codes but figured that I pumped a bunch of them into it with all of my testing so just shined it on for now.
    I'm wondering if the Manifold Air Temperature sensor could be bad or if it would make any difference. Do you test that by checking its resistance difference between when it's cold and when it's all warmed up and in closed loop?

    I assume that the TPS is OK, since it has been running fine. The coolant temp sensor is registering as it should. So, I guess my main question is ... should the computer be changing the on and off flow of the EGR solenoid when testing it the way that I did? If it should be changing, then what could be causing it not to?

    Thanks in advance for any and all replies.

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  3. #2
    kingjoel is offline Cadillac Owners Member
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    Re: No vacuum to EGR valve ... 4.9 engine

    My 92 Seville does just as yours, code E048. I replaced the EGR valve and nothing changed. In my car the heater-defroster air vents don't seem to change when pushing the defrost button. Also the park brake releases slow or not at all. A big problem is high RPM when shifting for the first 5-10 miles of operation, after that it shifts fine. I can't help thinking they are all vacuum related but I'm not sure. Good luck I hope you get an answer about the solenoid.

  4. #3
    runforrest1 is offline Cadillac Owners Member
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    Re: No vacuum to EGR valve ... 4.9 engine

    Well, as they say "Misery loves company". In this case maybe two heads are better than one working on the same problem. I changed the EGR valve. I got the new one at Auto Zone. I hope they gave me the correct one.
    I went back to the smog shop for a retest and failed again. It was the same thing .. high NOx, only this time there was some improvement. The first reading was 15 mph-1290 ppm, 25 mph-1054 ppm.
    The retest was 15 mph-1039 ppm, 25 mph-928 ppm.

    I hooked a vacuum gauge inline with a "T" connector between the solenoid and the EGR valve. I used a long hose so that I could be behind the wheel and tacked it up with it in gear and foot on the brake. After about 2000 rpms the reading was about 3 inches and then would drop to zero when I got it up to about 3000 rpms. I couldn't tell whether the EGR was opening or not.

    What to do next? I checked the EGR tubes in the throttle body and the smaller diameter one to the rear was a little clogged. I took a .22 caliber bore cleaning brush to them with throttle body cleaner. I also dropped the timing down to about 9 degrees BTDC from what looked like about 11 degrees ... hoping that will make it run a little cooler. The book calls for 10 BTDC and the test allows plus or minus 3 degrees.
    I'm going to go out this evening and play around with reading codes, which I still have to figure out how to do.
    I can't help but think that the low restriction cat from Magnaflow is causing the positive back pressure EGR valve to not work right.

    By the way, my parking brake was not releasing all the way. I had to put my toe under the pedal and lift up. I think my son or wife pulled something loose and now I have to reach up under there and yank on a cable to get it to release.

    Anywhooo ... any thoughts or comments on this EGR problem would be greatly appreciated.

  5. #4
    runforrest1 is offline Cadillac Owners Member
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    Re: No vacuum to EGR valve ... 4.9 engine

    Quote Originally Posted by kingjoel View Post
    My 92 Seville does just as yours, code E048. Also the park brake releases slow or not at all.
    I just did some inspection of the parking brake. I don't know what's wrong with mine ... doesn't release when you put it in gear, as it should, but did find that there is a manual release lever attached up under there. I just now took a piece of fairly thick bailing wire and put it through the hole in it and made a loop in it for a handle and dropped it down about six inches. Without that, I doubt if anybody else would be able to figure out how to release the sucker.

    EGR .. what to say? I just read that there are passageways under the throttle body corresponding to the two tubes in the throttle body that can become clogged with carbon and might have to be cleaned or drilled out. I just checked for codes and came up with nothing. I did get someone to put their foot on the brake and torque it up to about 2500-3000 rpms. I put my finger under the EGR valve and could feel the diaphragm moving up, so hopefully I'm making progress.
    You might want to check the same. Have you done any testing of the solenoid?

  6. #5
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    Re: No vacuum to EGR valve ... 4.9 engine

    If the parking brake does not auto release, you have a vacuum leak. Usually it is a disconnected vacuum line at the release diaphragm or a bad diaphragm (#21). Start by fixing the vacuum problem.

    http://www.gmpartsgiant.com/Page_Pro...PartSortBy=Key

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    kingjoel is offline Cadillac Owners Member
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    Re: No vacuum to EGR valve ... 4.9 engine

    runforrest1, I had my son rev up engine 2000-3000 rpm in park, no EGR movement. I will try in gear with foot on brake on warmer day (colder than hell in Ne). I'm still searching for vacuum leaks. I watched a video where a guy blew cigar smoke into a vacuum line to find leaks, I may try that on a warmer day.

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    Re: No vacuum to EGR valve ... 4.9 engine

    A FSM would be worth it's weight in gold right now as it will give you the exact parameters needed for the EGR solenoid to activate the vacuum valve. It's been too long for me to remember, but I would not rule out vehicle speed as one of the parameters.

  9. #8
    runforrest1 is offline Cadillac Owners Member
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    Re: No vacuum to EGR valve ... 4.9 engine

    [/COLOR]
    Quote Originally Posted by kingjoel View Post
    runforrest1, I had my son rev up engine 2000-3000 rpm in park, no EGR movement. I will try in gear with foot on brake on warmer day (colder than hell in Ne). I'm still searching for vacuum leaks. I watched a video where a guy blew cigar smoke into a vacuum line to find leaks, I may try that on a warmer day.
    I tried that and got no vacuum to the EGR. I had to put a load on the engine to get it to open the valve. I also discovered that the front of the car engine mount has already taken a dump. I replaced it less than a year ago. This time I'm going to use a solid mount instead of the hydraulic type.

    I think people also use a can of starting fluid or carb cleaner to find vacuum leaks. If you find one, it should change the idle RPM.

    ----------

    Quote Originally Posted by Ranger View Post
    If the parking brake does not auto release, you have a vacuum leak. Usually it is a disconnected vacuum line at the release diaphragm or a bad diaphragm (#21). Start by fixing the vacuum problem.

    http://www.gmpartsgiant.com/Page_Pro...PartSortBy=Key
    Thanks for the information about the parking brake. I wondered how that thing worked. I'll have a look up under there.
    I hosed it with WD-40 last night but it is still rather stiff and have to pull it up to get it in the completely released position.

  10. #9
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    delerium75 is online now Cadillac Owners Fanatic
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    Re: No vacuum to EGR valve ... 4.9 engine

    I'm currently having EGR issues with the Fleetwood too and saw the comment about the parking brake...checked yesterday and it's not releasing. So...the parts Ranger mentioned...#21 is near or on the foot lever right?

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    Re: No vacuum to EGR valve ... 4.9 engine

    Yup.

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    kingjoel is offline Cadillac Owners Member
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    Re: No vacuum to EGR valve ... 4.9 engine

    THANK YOU, to everyone! I found the vacuum line to a canister under the battery was old and collapsed. I replaced it and now my caddy shifts perfect, EGR valve works as it should. I cleared codes and no service engine soon light (so far). I only test drove it a couple miles but all seems well. Tranny service, EGR valve, and wrench to change probably was not necessary, oh well.
    Thanks again!

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    Re: No vacuum to EGR valve ... 4.9 engine


  14. #13
    runforrest1 is offline Cadillac Owners Member
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    Re: No vacuum to EGR valve ... 4.9 engine

    Well, just to update what I have been going through with this EGR problem. I flunked the first test due to high NOx, and replaced the EGR valve and then went for the second test, which I also flunked but with about a 50% reduction in NOx. I replaced the solenoid, cleaned out the throttle body tubes, reduced my base timing from about 11 degrees BTDC to about 8 degrees. We are allowed + or - 3 degrees in California and mine calls for a 10 degree BTDC.
    I took it back today for an unofficial test and it was down but still wouldn't pass.

    Well, say shit howdy .. broke out a six pack of Corona and started tearing off the throttle body. I cleaned the EGR tubes better than I had before and also discovered that the little rubber connecter tubes for the vacuum on a couple of lines where cracked and as hard as cooked plastic. I doubt if that will help my problem but glad that I discovered it and will replace them.

    Here's what almost gave me a heart attack. I removed the bolt from the EGR on the passenger side, set it out of the way and then loosened the other. After I had it all the way out, I lifted up the EGR valve and the damned bolt fell out of it an went into the manifold!
    If I ever doubted that God exists, I take it back. I found myself saying "Please God, let me get this out without having to tear this engine apart".
    In a furious panic I dug out my magnet on a stick, stuck it down into the EGR port where it fell into and couldn't see .... and
    there it was ... stuck like shit to a blanket. It came right out on the first try. There is a God after all!

    After that trauma I grabbed my roll of 2 inch wide blue painters' tape and covered the throttle body and EGR openings.

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    Re: No vacuum to EGR valve ... 4.9 engine

    It would not have been as big of a problem as you might have thought. I once dropped the distributor lock down nut down the distributor shaft hole of an HT4100. Spent several hours trying to fish it out with a magnet. Every time I latched onto it, the magnet would get sucked sideways and I'd loose it. After hours of this amusement park game I lost it one last time and heard the sickening sound of it hitting the oil pan...............................where it stayed for the rest of that engines life (several years that I am aware of).

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    runforrest1 is offline Cadillac Owners Member
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    Re: No vacuum to EGR valve ... 4.9 engine

    Quote Originally Posted by Ranger View Post
    It would not have been as big of a problem as you might have thought. I once dropped the distributor lock down nut down the distributor shaft hole of an HT4100. Spent several hours trying to fish it out with a magnet. Every time I latched onto it, the magnet would get sucked sideways and I'd loose it. After hours of this amusement park game I lost it one last time and heard the sickening sound of it hitting the oil pan...............................where it stayed for the rest of that engines life (several years that I am aware of).
    Yeah, I feel your pain ... but something down into the oil pan is nothing like something into the intake manifold. Once into the oil pan it's like a gold nugget in a sluice box, heavy and will stay there.

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