1988 Eldorado Emissions Through The Roof - EGR Vac Solenoid??
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Cadillac Seville / Cadillac Eldorado Forum Discussion, 1988 Eldorado Emissions Through The Roof - EGR Vac Solenoid?? in Past Cadillac Vehicle Discussion; I went to go smog my car last week because I finally fixed the tranny problem. Now, I failed emissions ...
  1. #1
    norfmo is offline Cadillac Owners Member
    Automobile(s): 1988 Eldorado Biarritz 4.5 V8 - 101,000 Miles
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    1988 Eldorado Emissions Through The Roof - EGR Vac Solenoid??

    I went to go smog my car last week because I finally fixed the tranny problem. Now, I failed emissions horribly and I need a little help to fix this. I also noticed that a grayish liquid comes from the tailpipe when revving engine, I believe its condensation, but there's definitely more then there should be.

    So first off, here's my HC and CO readings:

    HC @ 15mph = 65ppm
    HC @ 25mph = 363ppm

    CO @ 15mph = 2.55%
    CO @ 25mph = 10.56%

    CO2 @ 15mph = 13.10%
    CO2 @ 25mph = 7.40%

    O2 @ 15mph = 0.31%
    O2 @ 25mph = 1.19%

    NO @ 15mph = 32ppm
    NO @ 25mph = 51ppm

    Correct me if I'm wrong, but I think the CO and the HC are the only reasons why I didn't pass. They're through the roof.

    I had just replaced the spark plugs about 5000 miles ago, along with the cap and rotor. I just did wires about a month ago, less then 500 miles ago. And Im not getting a misfire at all. What else could be causing this?

    I thought it might have been the EGR Valve, but I did the test to see if pushing the diaphragm would lower RPMs and it worked. So, I kind of believe it may be the EGR vacuum solenoid.

    I read that the vacuum line going into the EGR from the solenoid should have vacuum at 2000 rpm when engine is warmed up. Mine doesn't have any vacuum at all, even as high as 3 or 4000 rpm. I think this may be where the problem is at. The vacuum hose isn't leaky either, it wasn't getting vacuum at the solenoid or at the end of the hose.

    I tested the plug going into the EGR vacuum solenoid and it was reading 13v, so the wire isn't shorted. Should this be creating some kind of suction at these rpms and if so could that be contributing to my hydrocarbon levels?

    And also, I noticed my idle rpm is at around 950. I think I read somewhere that it should be at around 550 for this car. Is that true and how should I test out where the problem is there?

    One more question too. I wanna test the cat to see if that's contributing to the CO, but I don't wanna create an exhaust leak that leaks when plugged up. What's the most efficient way to plug the pipes back up after i screw the holes?

    And any other advice on what could cause these emissions would really help. I'm sort of a beginner and I'm learning as I go, but I am handy enough to handle this. Just need to know some diagnosing procedures. Thank you all.

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  3. #2
    mhamilton is offline Cadillac Owners Connoisseur
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    Re: 1988 Eldorado Emissions Through The Roof - EGR Vac Solenoid??

    I read that the vacuum line going into the EGR from the solenoid should have vacuum at 2000 rpm when engine is warmed up. Mine doesn't have any vacuum at all, even as high as 3 or 4000 rpm. I think this may be where the problem is at. The vacuum hose isn't leaky either, it wasn't getting vacuum at the solenoid or at the end of the hose.
    The vacuum line to the EGR valve usually won't have any vacuum when the car is in park/neutral (not 100% sure on that year, but usually this is the case with PCM controlled EGR valves). Do you have vacuum at the input to the solenoid?

    I'm don't know what the passing limits are for your emissions levels--which are failures, CO and CO2? The EGR really only reduces NOx (oxides of nitrogen), the CO and HC is affected by mixture, and reduced further by the cat converter. I don't think it's worth trying to disconnect the cat, if it's worn out you'll see that in tailpipe emissions. The only reason to disconnect the cat is if you suspect it's clogged, which isn't the issue here, I don't think.

  4. #3
    carnut is offline Cadillac Owners Master
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    Re: 1988 Eldorado Emissions Through The Roof - EGR Vac Solenoid??

    If the car is not reaching normal engine temp. it will never go into closed loop. Should be approx 195 to 210 F. If the Oxy sensor does not reach temperature, then it will not control the mixture. EGR only affects NOX emmisions. Replace the thermostat with a 195 degree one, add a gallon of denatured alcohol to a half tank of gas and have it retested. You can monitor the engine temp in celcius thru on board diagnostics. Should be approx 95 to 100 degrees Celcius. Hard to believe a car running this rich would not set a code? and have a service engine now light on.

  5. #4
    drewsdeville is offline Cadillac Owners Master
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    Re: 1988 Eldorado Emissions Through The Roof - EGR Vac Solenoid??

    As stated, whether in closed loop or not, the EGR does not function in park or neutral. There should be no vacuum applied to the valve when in P or N.

    Is the AIR system working correctly? Air pump should be pumping to the diverter valve, and the diverter should be routing the air to the cat when at operating temp. If it's not, the car will fail, even if it's running perfectly in every other respect. It's very easy to check. When the car is at operating temp, idling, start pulling hoses off, one by one, at the diverter valve. Feel with your hand which ones have air coming out of them and find out where they go. The diverter valve sending air to anywhere but the cat is incorrect, making the diverter valve your problem.

    Onboard diagnostics will tell you a lot.


    When in onboard diagnostics, enter the PCM parameters. If the "AUTO" light is lit on the climate control display while in this mode, the PCM is in closed loop. That's a good thing. If not, THEN try carnuts advice.

    If the car is in closed loop, then the fuel trim is being adjusted. You can tell what the PCM is actually doing with the fuel trim by going into the onboard diagnostics and looking at the integrator (INT) value. Any value significantly greater than 128 means the PCM is adding fuel from the baseline mapping. You can better diagnose when you know what the PCM is trying to do. From this, you can tell if the car is running rich or lean.

    Since you say the car runs perfectly otherwise (I'm assuming this means mpg's are still good), I'd really suspect the AIR system. The diverter valve is the most common failure point in the system. When it fails it routes air to the wrong place (usually the air cleaner) rather than diluting the exhaust with fresh air as it should.

  6. #5
    norfmo is offline Cadillac Owners Member
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    Re: 1988 Eldorado Emissions Through The Roof - EGR Vac Solenoid??

    Thanks for all the help.

    I think it's the HC and the CO that failed. I'm not sure at this point how the mpgs are. I haven't driven it enough to get a correct reading since it's last been reset. The car isn't registered at the moment so that's why I'm so desperately trying to pass smog.

    Where is the diverter valve located? And, what lines should have air blowing out and what shouldn't? As I said, I'm learning as I go and my knowledge is very limited at this point. I have a Haynes manual but am sort of disappointed in it.

    Also, I know how to pull the codes on the OBD, but that's about it. How do I navigate to get the readings you're explaining? And by getting these readings, will that tell me if I need a 195 degree thermostat like carnut said?

    And when I was going to test the Cat, I wasn't going to pull it off. I read that I can drill a small hole behind the cat to test the pressure, then in the front of it to see if any pressure is built up. I was asking what the best way was to plug the holes after they were drilled, but with what I've learned, if it's a bad cat it should be causing some sort of driving problems right?

    Thanks again for all the help its really appreciated.

  7. #6
    VEGASELDO91 is offline Cadillac Owners Fanatic
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    Re: 1988 Eldorado Emissions Through The Roof - EGR Vac Solenoid??

    Check the vacumn hose connected to your MAP sensor, this was the cause of my emissions failure last year. Make sure you check the entire hose, at first I only inspected the end connected to the sensor. It was the other end that was cracked and blocked, replaced the hose and it passed effortlessly!! This is just a suggestion, hope it helps!

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