Cleaning the throttle body on a 4.9
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HT4100 4.1, 4.5, 4.9 Discussion, Cleaning the throttle body on a 4.9 in Cadillac Engine Technical Discussion; I'm sure you folks have chatted about this endlessly (I'm a new guy on this wonderful forum) but I'm doing ...
  1. #1
    Nick93SDV is offline Cadillac Owners Member
    Automobile(s): 1993 Sedan Deville; 1997 Deville D'Elegance; 2010 DTS
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    Cleaning the throttle body on a 4.9

    I'm sure you folks have chatted about this endlessly (I'm a new guy on this wonderful forum) but I'm doing my first 120k maintenance on my '93 SDV and want to make sure I'm doing the throttle body cleaning right.

    I pulled off the plastic air ducts to expose the throttle body and while it looked clean enough (certainly compared to some of the scummy looking carbs on my other cars), I sprayed some generic carb and choke cleaner around the exterior and down the two throats. Some gluck was dislodged on the throats but there remains a slight ring of dark material right where the plates touch the throat at the rest\off position. The only way I imagine that I could get that last little bit off would be to push the plates out of the way and then wipe off the ring. But when I gingerly push a little bit on one of the plates, it didn't move at all (I didn't press the matter) and so I did the best job I could without actually moving the plate. Here are my questions.

    1) Is it possible to move the plate by hand in order to better access the tiny ring of dark residue? If so, how? Is removing that ring all I need to do or should I also be concerned about any residue below the plates?

    2) Should I run the car and spray the cleaner down the two throats of the throttle body as suggested by the instructions? If so, should I gun the engine while doing so? Anything I shouldn't do?

    3) The shop manual suggests that any throttle body cleaning should be followed up with a complicated resetting process to zero out the at-rest position of the throttle plate (at least that's my interpretation). Do you folks usually do the same thing?

    4) Are there other things I need to do to the throttle body unit? At the moment, the car is running fine (about 19 MPG avg in the city) but I'd like to scratch this off the list.


    Thanks, as always...

    Nick

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    BeelzeBob's Avatar
    BeelzeBob is offline I'm a Cadillac Fanatic!
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    Re: Cleaning the throttle body on a 4.9

    Quote Originally Posted by Nick93SDV
    I'm sure you folks have chatted about this endlessly (I'm a new guy on this wonderful forum) but I'm doing my first 120k maintenance on my '93 SDV and want to make sure I'm doing the throttle body cleaning right.

    I pulled off the plastic air ducts to expose the throttle body and while it looked clean enough (certainly compared to some of the scummy looking carbs on my other cars), I sprayed some generic carb and choke cleaner around the exterior and down the two throats. Some gluck was dislodged on the throats but there remains a slight ring of dark material right where the plates touch the throat at the rest\off position. The only way I imagine that I could get that last little bit off would be to push the plates out of the way and then wipe off the ring. But when I gingerly push a little bit on one of the plates, it didn't move at all (I didn't press the matter) and so I did the best job I could without actually moving the plate. Here are my questions.

    1) Is it possible to move the plate by hand in order to better access the tiny ring of dark residue? If so, how? Is removing that ring all I need to do or should I also be concerned about any residue below the plates?

    2) Should I run the car and spray the cleaner down the two throats of the throttle body as suggested by the instructions? If so, should I gun the engine while doing so? Anything I shouldn't do?

    3) The shop manual suggests that any throttle body cleaning should be followed up with a complicated resetting process to zero out the at-rest position of the throttle plate (at least that's my interpretation). Do you folks usually do the same thing?

    4) Are there other things I need to do to the throttle body unit? At the moment, the car is running fine (about 19 MPG avg in the city) but I'd like to scratch this off the list.


    Thanks, as always...

    Nick

    Put your hand on the throttle lever outiside the throttle body and open the throttle blades. If all else fails...have someone sit in the car with their foot firmly planted to the floor on the accelerator (obviously with the engine off and the keys in YOUR pocket....) That will get the blades open. Spray and clean the inside of the bores where the blades contact the bore of the throttle body and the backside of the blades to get all the deposits off. The buildup of deposits restricts the airflow around the blades and will cause idle speed control difficulties if allowed to build up too much. You're just trying to get the bore and backside of the blades clean for idle speed control accuracy...it has absolutely nothing to do with performance or driveability.....

    When you clean the throttle body good just disconnect the negative battery cable for 30 seconds and then reconnect. Good time to check the terminals for cleanliness/corrosion/tightness. That is all that is required to reset the idle speed control learn values. The ISC learns "offsets" to account for the deposit buildup. Now that you have removed it (cleaned the throttle body) the ISC system can start fresh...so disconnect the battery to reset the values. That is all that is required. Just drive the car after that.

    While you have the throttle blades wide open look down the throttle bores and see the two tubes sticking up at you from the floor of the manifold. those are the EGR delivery tubes and should not be full of carbon and such.... Rod them out with a piece of stiff coat hanger wire to clean them out. This will do more to improve the driveability of the system than anything at high miles.


    As long as you are doing a "tune-up" go to the set timing mode by shorting the ALDL pins A and B together (the ALDL connector is the "diagnostics connector under the dash by the steering column) and use a timing light to check the distributor reference setting. It should be at 10 normally in the set timing mode. Bump it up to 13-14 degrees for a little more power if you use premium fuel. The spark cal is a little conservative in that package due to the fact that the engine does not have a knock sensor...so you will have to use good gas to get the max power at the peak timing point....

  4. #3
    up2ng's Avatar
    up2ng is offline Cadillac Owners Member
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    Re: Cleaning the throttle body on a 4.9

    I keep old toothbrushes around just for jobs like this. It works wonders with carb cleaner and the plates

  5. #4
    Ralph's Avatar
    Ralph is offline Cadillac Owners 10000+ Posts
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    Re: Cleaning the throttle body on a 4.9

    Bob, thanks for the timing advance tip, I always run premium or it knocks.

  6. #5
    BeelzeBob's Avatar
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    Re: Cleaning the throttle body on a 4.9

    Quote Originally Posted by Ralph
    Bob, thanks for the timing advance tip, I always run premium or it knocks.
    You can still try bumping up the timing a degree or two.... That engine is several degrees off the optimum value at full throttle so if the fuel you are using can stand it without knocking then bumping it up a few degrees will give you a little more power. Just listen for the sound of "top dead ping" and back off the spark until is just barely goes away.

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