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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, My Sixty Special is explosive in Past Cadillac Vehicle Discussion; You need to get it up to normal operating temperature. Enter diagnostics and retest the PCM tests. Your O 2 ...
  1. #31
    dennis93coupe's Avatar
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    Re: My Sixty Special is explosive

    You need to get it up to normal operating temperature. Enter diagnostics and retest the PCM tests. Your O 2 sensor voltage should be at a higher and swing lower than what you posted. If it stays at the same voltage or close to the same, then I would say you have a bad O2 sensor. Loose spark plug wire can contribute to unburned fuel in that cylinder...

  2. #32
    DReffects's Avatar
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    Re: My Sixty Special is explosive

    Did a test drive today at normal operating temperature. the o2 sensor voltage fluctuated constantly between .3 and .8 volts. So that would be pretty normal then?

    Still got the harsh ingition dropouts when slowly accellerating. i've just checked the EGR diaphragm. Tried to push it up with my fingers. I have no comparison but it wasn't moving easily. I've pulled the tiny hose from the EGR valve - there was liiiiitle bit of suction - is that normal? Next up: I'll remove the EGR Valve completely and check for dirt.

    Spark Plugs and wires didn't change a thing

  3. #33
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    Re: My Sixty Special is explosive

    There should be no vacuum supply to the EGR valve at an idle... With the onboard diagnostics, you will be able to test both the solenoid that supplies EGR vacuum, and the valve itself.

    The valve SHOULD be somewhat difficult to push up.

    The O2 voltage sounds ok. It should fluctuate across the 0.45 mark constantly. The Cross Counts value in the OBD system will tell you how many times per second that is occuring

  4. #34
    DReffects's Avatar
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    Re: My Sixty Special is explosive

    Thanks for the feedback.

    I've got a new EGR Valve - it seems to behave exactly like the original one. We did a vacuum test with the valve by applying a vacuum pump to it. we were not able to get any vacuum at all. the new valve behaves the same way. The valves i know of from german cars behave differently. Is it normal that no vacuum can be applied?! if so, how does the valve get pushed/sucked up?!

  5. #35
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    Re: My Sixty Special is explosive

    This EGR valve is a positive backpressure type - it only operates when exhaust backpressure is sufficient - which it's not at idle. There are two diaphragms in this valve. Exhaust backpressure pushes on the lower, creating a seal so that vacuum can pull on the upper.

    You will need to rev the engine enough to properly test the EGR with a vacuum supply.

  6. #36
    DReffects's Avatar
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    Re: My Sixty Special is explosive

    ahhhhh thanks!

    i've installed the new egr valve, unfortunately it did not change much from what I can tell

    I've tested the Vacuum that goes to the EGR solenoid. There's vacuum present.
    I've tested the vacuum from the solenoid to the valve.
    There is no vacuum present when the motor is in idle and the connector is attached to the solenoid.
    There is vacuum present when I disconnect the connector of the solenoid.

    So....shoudn't the EGR valve lift up if I disconnect the connector from the solenoid and then the engine should stall? For me nothing happens when the vacuum from the egr solenoid is being let through to the valve. When i manually lift up the diaphram from the new valve the engine stalls.

    ----------

    here's a pic of the old valve. looks to me that the valve wasn't active for a long time...


  7. #37
    DReffects's Avatar
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    Re: My Sixty Special is explosive

    Unfortunately the new valve didn't solve the problem. For some reason the E48 error is gone, but the car behaves the same as before. from 60-75 mph i have horrible misfires, stuttering and stuff while pressing the gas pedal slightly.

    I've tested the EGR solenoid connector for a faulty ground, found none.
    I've tested the RPM drop for each cylinder with the PCM Override - all cylinders drop the same amount.
    I've replaced both spark plugs and wires, no change.
    I've checked the fuel pressure vacuum hose - it's NOT wet.
    O2 sensor readings are supposedly ok, too.

    I tried to do the "Emissions Performance Test" from Chart A-7. Unfortunately i was not able to figure out what the "canister purge line at throttle body" is supposed to be. Vacuum response from the EGR solenoid is as it should be, 15-16 inches of vacuum within 1 second. PCM has the ability to control the solenoid. (Tested with override E.5.2). The only odd thing i've encounterd is, that while trying to do the chart entitled "Diagnostic Trouble code E48 - EGR System Problem, Page 2 of 4) the RPM did NOT drop.

    The test procedure is being explained like this:

    - Connect Tachometer
    - Start Engine
    - Allow engine to reach normal operating temperature
    - Use Override E.5.2 EGR solenoid
    - Raise RPM to ~2.000
    - Press and hold WARMER button
    - RPM shloud DROP at least 100 RPM

    the odd thing: RPM actually ROSE 100-150 RPM.

    I am totally out of ideas Anyone?

    Thanks!

  8. #38
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    Re: My Sixty Special is explosive

    Earlier you posted the fuel trim values - were those taken while the engine stutter was occurring or just while sitting idle in the driveway?

    If they weren't taken while the problem was happening, take another look. Those values are dynamic and reflect current conditions. Recreate the stuttering at cruise. While the engine is stuttering, view the block learn and integrator values and post them here.

    Better yet, take down all PCM DATA values with the engine stuttering and report back...

  9. #39
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    Re: My Sixty Special is explosive

    Quote Originally Posted by drewsdeville View Post
    Earlier you posted the fuel trim values - were those taken while the engine stutter was occurring or just while sitting idle in the driveway?

    If they weren't taken while the problem was happening, take another look. Those values are dynamic and reflect current conditions. Recreate the stuttering at cruise. While the engine is stuttering, view the block learn and integrator values and post them here.

    Better yet, take down all PCM DATA values with the engine stuttering and report back...
    pew easier said than done. when the issues are happening the car is pretty much undriveable. after just a few seconds i have loud pops and bangs, proposedly from fuel exploding. those values were taken while driving normally. I'll do my very best to get some more values while the issues are present.

  10. #40
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    Re: My Sixty Special is explosive

    Did you change the cap and rotor? How about compression test? Does it behave like that when you are at a slow speed and punch it? You might need to check the valve train to see if you have a lifter/camshaft problem. I doubt it's that and tend to lean towards an electrical issue.

  11. #41
    DReffects's Avatar
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    Re: My Sixty Special is explosive

    What cap and rotor? I've changed the radiator cap. Cylinder compression test showed no problem. Did the RPM drop test for that and also a manual compression test while replacing the spark plugs. Could a fauly head gasket cause this kind of problems?

  12. #42
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    Re: My Sixty Special is explosive

    Quote Originally Posted by DReffects View Post
    What cap and rotor? I've changed the radiator cap.
    The distributor cap and rotor.

    Quote Originally Posted by DReffects View Post
    Could a fauly head gasket cause this kind of problems?
    I doubt it if you had consistant compression as you stated when you had the plugs out. I have heard what a flat camshaft sounds like, but find it hard to imagine that is your problem.

  13. #43
    DReffects's Avatar
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    Re: My Sixty Special is explosive

    The Distributor cap looked like new when we've took the thing apart. is there a way i can test it?

  14. #44
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    You can test the ICM, but you can't really "test" the cap and rotor. If the contacts look good, and there's no carbon tracking, they're fine.

  15. #45
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    Re: My Sixty Special is explosive

    did you ever check the fuel injectors?

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