1991 Fleetwood (Special Sixty): Throttle response & engine running rough
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, 1991 Fleetwood (Special Sixty): Throttle response & engine running rough in Past Cadillac Vehicle Discussion; ...
  1. #1
    Tiedemate is offline Cadillac Owners Member
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    1991 Fleetwood (Special Sixty): Throttle response & engine running rough

    Hello to the cadillac forum,

    having bought our 1991 model Fleetwood Special Sixty 4.9l a couple of weeks ago, we've just recently experienced an increasingly rough engine running, a rather shaky throttle response and occasional misfire. This thread then is our attempt to get the experts of you involved in the hope to receive a few valuable hints. Thanks in advance.

    Here it goes:
    My friend managed to check the OBD and got a reading of the indicated faults. It displayed E52 (voltage breakdown), E55 (throttle position sensor misadjustment) and E99 (malfunction of cruise control adjuster).
    He managed to check the value of a number of sensors as well. Does anyone know if the following values for the sensors appear to be correct or might indicate a malfunction?
    TPS: Value between 7.6 and 78.7 (idle to full throttle)
    EGR pintle position: At engine off: 7, at engine running: 13.6 (no alternation of the value, regardless of throttle position)
    Ignition ground voltage: Always "0" (is this normal???)

    Having thought the rough engine might be due to a clogged up EGR, we cleaned the backflow pipes. This didn´t seem to have a strong effect. We then looked into the ignition system and decided it was a good idea to sandpaper the contacts of the ignition distributor (which appears to have made things worse).

    Having discovered that the work on the ignition distributor seemed to have an effect on the problem, our plan now was to change the following components of the ignition system: Ignition coil, fit new tune-up kit, spark plugs and hall sensor. Any opinions on that? Also on this note: Does anyone know whether there is a magnet mounted on the "ignition distributor shaft" or does teh magnet come seperately?

    If some of you have a lifesaving tip, a valuable opinion or an encouraging comment, we'd be happy to find out about it!!

    Thank you very much indeed!!

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  3. #2
    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
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    Sensor output value ranges would be listed in the Factory Service Manual.

    P052 - PCM memory reset. Don't worry about this one. Has the battery been disconnected recently?

    P055 - Closed throttle angle out of range. This could be due to a bad or misadjusted TPS, or there may be a problem with the ISC motor. What is the idle speed?

    I would suggest replacing the plugs, wires, cap and rotor.

    Not sure what you're referring to by magnet on the distributor shaft.

  4. #3
    dennis93coupe's Avatar
    dennis93coupe is offline Cadillac Owners Connoisseur
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    Re: 1991 Fleetwood (Special Sixty): Throttle response & engine running rough

    First thing I'd do is take a trip over to ebay and grab a FSM. Your best source of information for specifications regarding values in diagnostics.

    http://www.ebay.com/sch/i.html?_odkw...1&_sacat=34212

  5. #4
    Tiedemate is offline Cadillac Owners Member
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    Re: 1991 Fleetwood (Special Sixty): Throttle response & engine running rough

    Hey guys,

    thanks for the replies! We've ordered a factory service manual plus a few parts for the ignition system (plugs, cap, rotor, wires, ICM, hall sensor thingy, ignition coil). Yes, it is a bit firing the parts bazooka without diagnosing properly, but shipping is more expensive than the parts and we're a bit limited on time, so we have to maximise the probability that the first shot cures it. We've not ordered the pickup coil since I read that the car wouldn't run at all if it's shot, is that correct?
    I wanted to adjust the TPS, but the fuel data center wouldn't display the engine speed (should be PD11 I think, but after PD10 it jumped to PD12). I have ordered a handheld rev counter to fix that...
    If I adjust the minimal air with the low idle controller out of the way to do the TPS adjustment afterwards, what is target value for engine speed? I have found 450rpm, 500rpm and 550rpm in different posts.

    Thanks again and we'll keep you posted!
    Björn

    PS: The car is bound to take us on this journey http://www.thegreatrally.com/routes/...uropean-rally/ ;-)

  6. #5
    dennis93coupe's Avatar
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    Re: 1991 Fleetwood (Special Sixty): Throttle response & engine running rough

    When you get your FSM, read it carefully. What you have read in posts can be different than what is in that manual. Everything is in there, just takes a little time digging it out. You will want to start in section 6, driveability and emission control.

  7. #6
    Tiedemate is offline Cadillac Owners Member
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    Still waiting for the FSM to arrive, I'll keep you updated...

  8. #7
    Tiedemate is offline Cadillac Owners Member
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    So, finally we replaced the spark plugs, wires, distributor cap and rotor, and she is running very well again. A slight shake is left in low idle, but otherwise the engine is running smooth and pulls well. Thanks for the tips!
    I am not yet the biggest fan of the FSM though. For example the spark plug gap is mentioned in the index, but not on the page the index refers to. We also wanted to check ignition timing, but I couldn't find the pinout of the ALDL anywhere in the book. Maybe I just have to get used to it...
    However the car is running fine and we're all set for our journey!
    Thanks a lot!

  9. #8
    mc_marto's Avatar
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    Re: 1991 Fleetwood (Special Sixty): Throttle response & engine running rough

    There is another way you can put the computer into set ignition timing mode. Look for the PCM outputs in the FSM - it should be called Fixed Spark Timing or something like that. I am not aware if your on-board menus are the same as the ones on my Deville's. The way I got to the menu was as follows: !1)Off + Warmer to enter diagnostics, 2) after you have 7.0 on the FDC display depress Hi, 3) after you see the display change (I don't recall the parameter at the time) hold Econ + Warmer, 4) the display should show E.5.0, 5) go with Hi or Lo to E.5.9. That is the Fixed Spark Timing - it will display the current ignition timing the PCM is commanding. If you press Cooler once the display should read 10 - this is the set ignition timing mode through the menu - no need for jumping at the ALDL. Once you're there you can check and adjust the timing if needed.

    Hope this helps. Consult with the FSM if the menu structure is the same - it should be, considering it is the same engine.

  10. #9
    brougham is offline Cadillac Owners Master
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    Re: 1991 Fleetwood (Special Sixty): Throttle response & engine running rough

    Im not sure on those cars but a lot of them there is also a wire under the hood you can disconnect when you set the timing.

  11. #10
    Tiedemate is offline Cadillac Owners Member
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    Re: 1991 Fleetwood (Special Sixty): Throttle response & engine running rough

    So after we've exchanged the iginition stuff we didn't do anything else and set off on our 4000kms Euro trip; and all went very well! (Apart from some power steering fluid leaks under heavy load). Back home a hail storm struck and shattered the wind screen, bad luck...

  12. #11
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: 1991 Fleetwood (Special Sixty): Throttle response & engine running rough

    That's good to hear that it is running good. Too bad about the windshield. I usually don't get too upset if the windshield is old and pitted because a new one is so nice. I hope availability isn't a problem in your area.

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