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5.0 and 5.7 Discussion, Ping in Cadillac Engine Technical Discussion; Hello, Recently, my 93 Fleetwood (161,000 miles) has started mild "pinging" at moderate throttle settings. The timing is dead-on. Shouldn't ...
  1. #1
    Timothy60 is offline Cadillac Owners Fanatic
    Automobile(s): 1993 Cadillac Fleetwood
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    Oct 2005
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    Syracuse, NY
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    Ping

    Hello,
    Recently, my 93 Fleetwood (161,000 miles) has started mild "pinging" at moderate throttle settings. The timing is dead-on. Shouldn't the knock sensor detect the pinging and retard the spark? It does not throw any codes. I've tried a tankful of high-test but it made no difference. Any ideas? Your suggestions are appreciated.
    Tim

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  3. #2
    caddycruiser's Avatar
    caddycruiser is offline Cadillac Owners Connoisseur
    Automobile(s): '93 Fleetwood Brougham...Dad's
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    Re: Ping

    When our '93 did it, and did it pretty badly, the EGR valve was bad and replacing it & the solenoid cured it completely. Of course, ours also registered the -32 code for EGR, which was how the dealer figured it out, so it may not be your problem. But you never know.

  4. #3
    90Brougham350's Avatar
    90Brougham350 is offline Cadillac Owners Connoisseur
    Automobile(s): 94 FWB, 93 SDV, 94 FWB (sold), 90 Brougham (sold)
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    Re: Ping

    Be very weary of exhuast leaks. In the right places, they can sound identical to pinging. Then you spend weeks pulling your hair out trying to get the timing perfect, checking for for codes, wondering if you have bad wiring somewhere.....ask me how I know!

  5. #4
    BCs71's Avatar
    BCs71 is offline Cadillac Owners Enthusiast
    Automobile(s): 1994 Cadillac Fleetwood Brougham (some show and some go!)
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    Chicagoland
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    Re: Ping

    If you still have the original knock sensor then I would be weary of the frequencies it is sending now... probably a good maintenance item to swap out at 100K+ miles.

    Also, (edit) excessive carbon build-up which would not be uncommon for your mileage can reduce combustion chamber volume and "timing being right on" becomes relative. Pinging results. You may be able to band-aid the problem by stepping up to higher octane fuel. Best fix is to decarbon the piston tops through the shadetree method (can of Seafoam for $5) or the pro way for $100-150 via Motorvac at a mechanic's shop.

    First thing I'd try is a new knock sensor. Be sure to get torque setting correct as it can affect sensitivity levels from what I understand...

  6. #5
    Timothy60 is offline Cadillac Owners Fanatic
    Automobile(s): 1993 Cadillac Fleetwood
    Join Date
    Oct 2005
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    Syracuse, NY
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    Re: Ping

    Looks as if I need to narrow it down to an EGR, knock-sensor, exhaust leak, or carbon build-up. Also, could it be that old plugs are creating hot spots in the combustion chambers? I'll adress the easiest things first and see what happens. Gentleman, I appreciate your input. I read about misting some distilled water into the throttle venturi at about 2000 RPM to "steam clean" the carbon from the heads. Have you ever tried that?

  7. #6
    90Brougham350's Avatar
    90Brougham350 is offline Cadillac Owners Connoisseur
    Automobile(s): 94 FWB, 93 SDV, 94 FWB (sold), 90 Brougham (sold)
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    Re: Ping

    Seafoam is much more effective. It works very well.

  8. #7
    Timothy60 is offline Cadillac Owners Fanatic
    Automobile(s): 1993 Cadillac Fleetwood
    Join Date
    Oct 2005
    Location
    Syracuse, NY
    Posts
    150

    Re: Ping

    The knock is gone! I decided to try the easiest, cheapest solutions first. I was even too cheap to buy a can of Seafoam or GM TEC spray, but I did spring for a gallon of distilled water. I got the engine up to operating temperature and trickled 8 ounces/30 seconds of water down into the throttle bores at 2000 RPM. A mushroom cloud of steam came out of the tailpipe. Buttoned up the air cleaner and took the Caddie for a spin. Knock completely gone. I read about how to do this in the September 2000 Car Talk archives. Tomorrow on my way to work I'll do a WOT blast just for good measure.

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