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HT4100 4.1, 4.5, 4.9 Discussion, Thoughts on the 4.5 in Cadillac Engine Technical Discussion; Throttle Body Injection (TBI) was largely a stop-gap measure that GM used from about 1982 (correct me if I'm wrong, ...
  1. #16
    awadecki is offline Cadillac Owners Enthusiast
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    Re: Thoughts on the 4.5

    Throttle Body Injection (TBI) was largely a stop-gap measure that GM used from about 1982 (correct me if I'm wrong, but I think GM's 2.5L I-4 was the first GM engine to use TBI in 1982) through 1995 (when it was discontinued on the full size SUVs and pickups).

    Throttle Body Injection meters fuel into the top of the intake manifold, very similar to a carburetor. GM employed 1 and 2 injector TBI setups (all Cadillac V8s used 2 injectors--similar to a 2bbl carb).

    TBI was a cheap, but effective and reliable system that offered considerable improvement over a carburetor without much complexity. A typical TBI system only has about 5 critical engine sensors (Manifold Absolute Pressure (MAP), Coolant Temp, Oxygen, Manifold Air Temp (MAT), Throttle Position).

    Port fuel injection, by contrast, meters fuel into the intake port right above the intake valve on EACH cylinder. There are two major types of PFI: batch fire and sequential fire. In batch fire PFI, all injectors fire at once, whereas in sequential fire (what was used on the 4.5, 4.9, and 3800 among others) each injector squirts fuel immediately before the intake valve opens.

    The disadvantage to batch fire injection systems is that a driver must wait until all 8 cylinders fire to respond to a throttle input (really not that long of a time), whereas sequential injection can respond immediately to throttle changes.

  2. #17
    90Devillex32 is offline Cadillac Owners Member
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    Re: Thoughts on the 4.5

    Thanks for the info. So my 90 deville is TBI?

  3. #18
    I~LUV~Caddys8792's Avatar
    I~LUV~Caddys8792 is offline Moderator
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    Re: Thoughts on the 4.5

    No, the 1990 4.5V8 is port fuel injected, the 88-89 4.5 is TBI.
    "They call Alabama the Crimson Tide, call me Deacon Blues."

    Current:
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  4. #19
    leftoverture is offline Cadillac Owners Fanatic
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    Re: Thoughts on the 4.5

    So the 90 Eldo I'm looking at would be port injected also?

    I really want this car, wish someone would buy my snowmobile. Might help if it snowed a few inches here.

    Ugghhh!


  5. #20
    I~LUV~Caddys8792's Avatar
    I~LUV~Caddys8792 is offline Moderator
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    Re: Thoughts on the 4.5

    Yes, all of the 4.5 Cadillacs in '90 were PFI.
    "They call Alabama the Crimson Tide, call me Deacon Blues."

    Current:
    1992 Lincoln Town Car Cartier Edition (5/14- ?)
    2014 Honda Accord LX MTX Sedan (1/14 -?)

    Past:
    1995 Buick Roadmaster Limited (4/04-12/04)
    1992 Cadillac Sedan deVille (12/04-9/07)
    1999 Mercedes Benz S320 (8/07-7/09)
    2000 Buick Regal GS (7/09-4/12)
    2003 Mercury Marauder (4/12-10/13)
    1991 Buick LeSabre Custom Sedan (9/12-6/13)
    2013 Honda Accord LX Sedan (6/13-1/14)

  6. #21
    awadecki is offline Cadillac Owners Enthusiast
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    Re: Thoughts on the 4.5

    Actually, now that I think about it, I think the 1980 Cadillacs used TBI on the 368 engine (FI systems on the 500 and 425 ci engines were port fuel injection). That might be the first TBI system. In 1982, the HT4100, the 2.5L I-4, and the Corvette/Camaro/Firebird Chevy V-8s received TBI.

  7. #22
    leftoverture is offline Cadillac Owners Fanatic
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    Re: Thoughts on the 4.5

    The great thing about TBI is it's simple and relatively cheap to fix.

  8. #23
    leftoverture is offline Cadillac Owners Fanatic
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    Re: Thoughts on the 4.5

    Crap. . .looks like the Eldo I was looking at is sold. Just couldn't sell the sled fast enough.


  9. #24
    behind-bars is offline Cadillac Owners Connoisseur
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    Re: Thoughts on the 4.5

    Does the 4.5 PFI use the same transmission as the 4.9 PFI?

    Theirs is a 90 Fleetwood for sale that I may try and take a look at, If it was nice and worked out the 93 Deville with a 4.9 would probably have to go

    I was curious if it engines were about the same (besides the difference between 4.5 and 4.9). Didnt want to trade down in a sense and end up buying a more problematic car.

    IIRC the electronic trans first came out in 93 so I guess the transmissions would be different. My deville is at 97k so its still healthy, not sure the mileage on the 90 Fleet though, If it sounds ok ill try and take a look at it and check codes and whatnot.

  10. #25
    behind-bars is offline Cadillac Owners Connoisseur
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    Re: Thoughts on the 4.5

    Just remembered this site, http://www.motorera.com/cadillac/cad...990/CAD90F.HTM

    It is indeed a different trans then I have now, Since the torque is lower should that make it considerably more reliable?

  11. #26
    MachX's Avatar
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    Re: Thoughts on the 4.5

    First, the electronic tranny came out in 91 with the 4.9 engines. And I'm not sure, but both my 4.5 and 4.9 knock rather loudly when I fire them up cold, but it goes away after a few minutes of running, I don't know if that is the 'main-bearing thump' people have described or if there is a bearing knock similar to a TON of Chrysler 4 bangers. Both engines are near identical and share many parts.

  12. #27
    99Zee28's Avatar
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    Re: Thoughts on the 4.5

    I unfortunately have a small crack in my block right under the starter. My buddy who owns a shop found it by accident when he had to take my starter off to do something. I heard that those cracks in that place is common on the 4.5 and to not really worry about it. Not sure how true that is. Other than that the car has been great! Also, only have 116,000 miles on it.

    Dave

  13. #28
    Jenns90seville is offline Cadillac Owners Member
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    Re: Thoughts on the 4.5

    I also have the cold weather piston slap. It goes away after the engine gets warm.

  14. #29
    99Zee28's Avatar
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    Re: Thoughts on the 4.5

    Quote Originally Posted by Jenns90seville View Post
    I also have the cold weather piston slap. It goes away after the engine gets warm.

    That is normal, always had that on mine too! Most GM engines or almost any engine for that matter has that. I just bought a new Monte Carlo with the 3.5 and surprisingly even when it was -10 out this past winter it didn't have any piston slap. I guess GM's tolerances are getting tighter.

    Later,
    Dave

  15. #30
    MachX's Avatar
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    Re: Thoughts on the 4.5

    Well after some research, I've discovered that the hybrid mix of aluminum blocks and iron heads causes piston slap because of the fact that aluminum expands faster than iron. So I've stopped worrying about the cold slap. After 4 years of driving these cars I've gotten used to it.

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