tuning Questions for a 93 deville
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HT4100 4.1, 4.5, 4.9 Discussion, tuning Questions for a 93 deville in Cadillac Engine Technical Discussion; I have a 90 factory service manual to work on a 93. I know the 90 came with a 4.5 ...
  1. #1
    lenny lincoln is offline Cadillac Owners Fanatic
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    tuning Questions for a 93 deville

    I have a 90 factory service manual to work on a 93. I know the 90 came with a 4.5 and the 93 came with a 4.9. Is the timing still set at 10*? I have a slight idle miss thats not throwing any codes. All new electrical components involed with a tune up where replaced except the coil pack. cleaned throttle plates front and back sides, cleaned the erg tubes, checked for vacumm leaks, none to be found. No lurching at cruising speed ,typical of a vacumm leak. thinking injectors clogged. getting occordingly to my FDC 9 miles to the gallon around town, which I think is wrong. Whats everbody eles getting? I am going to recheck the timing again tommorrow. Any other ideas?

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  3. #2
    behind-bars is offline Cadillac Owners Connoisseur
    Automobile(s): 93 Sedan Deville 4.9L
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    Re: tuning Questions for a 93 deville

    IIRC timing is 10* BTDC. mine has a decal under the hood saying what to set it at. 9 seems low, is their a new o2 sensor aswell?

    Im getting about 17 avg with a engine miss in light city driving, think plugs are my problem

  4. #3
    chubbyranger is offline Cadillac Owners Connoisseur
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    Re: tuning Questions for a 93 deville

    If you're going to adjust the timing there are usually two pins in the ALDL under the dash that you need to jump together to bypass the computer timing adjustment.

  5. #4
    lenny lincoln is offline Cadillac Owners Fanatic
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    Re: tuning Questions for a 93 deville

    I was thinking O2 replacement too. Might the fuel pressure regulator make the car run rich?

  6. #5
    behind-bars is offline Cadillac Owners Connoisseur
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    Re: tuning Questions for a 93 deville

    The FPR could be leaking which could result in bad gas mileage, IIRC people have said itll cause a miss aswell. Look in the tech tips for a thread on how to check for a leaky fpr. I know ive seen it mentioned in here several times

  7. #6
    lenny lincoln is offline Cadillac Owners Fanatic
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    Re: tuning Questions for a 93 deville

    the fpr will hold pressure using a mightyvac. I sprayed the inside of the diaphram slide bar with wd40. It seems to be getting better with driving. I never had it out on the highway since i got it 3wks ago and tuned it. I think the ecm is still learning. I did get a p040 powersteering switch code last night and tried to enter ecc to test it, BUt the part of pressing the brake pedal to let me get into that area of the ecc wouldnt work. I am using a 90 FSM tp work on a 93 so I think they might of changed something in the test procedure. I have to talk to a owner of a 93 FSM to find out.

  8. #7
    lenny lincoln is offline Cadillac Owners Fanatic
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    Re: tuning Questions for a 93 deville

    solved all problems but one. found out the cruise control swtich has to be turned on at 0.70 then you press the brake pedal. I have a bad power steering switch or it needs to be cleaned. I need to find where the switch is located. ANY help? After loving up the FPR with wd40 and a mightyvac idle smoothed out and held while I did the air flow adjustments. I now have a beautiful smooth idle. I need to do now is replace the lower O2 because of bad gas mileage to see if it helps. I am only getting 9 around town and its not throwing codes. And fix the powersteering switch.

  9. #8
    behind-bars is offline Cadillac Owners Connoisseur
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    Re: tuning Questions for a 93 deville

    Sorry, no idea for the PS Switch, I will say though that replacing the o2 is easy and your 93 deville should only have the one in the exhaust manifold under the hood. Took me 20 mins tops to replace mine.

  10. #9
    rstewart65 is offline Cadillac Owners Member
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    Re: tuning Questions for a 93 deville

    On a 90 the switch is on the side of the rack by the input shaft. I can emai a pic from the manual if you'd like, just post your address.

  11. #10
    rstewart65 is offline Cadillac Owners Member
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    Re: tuning Questions for a 93 deville

    Or look on page 3b-7 of the 90 manual, it's shown in figure 6 as item 6. (at least in my 90 FSM)

  12. #11
    lenny lincoln is offline Cadillac Owners Fanatic
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    Re: tuning Questions for a 93 deville

    I already saw the top 02 but when I went to autozone they said I had 2, So without looking I order the one after the cat. owning a lincoln towncar I learned that the rear one is the that does all the work . I will have to get under it to see how many I have. Thanks for the led on the location of the switch.

  13. #12
    behind-bars is offline Cadillac Owners Connoisseur
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    Re: tuning Questions for a 93 deville

    My 93 Deville only has one that i could see, didnt check after the cat though. It was 20$. If you had dual exhaust I would see the potential for more. Just replacing the one screwed into the exhaust up front fixed all my problems

  14. #13
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: tuning Questions for a 93 deville

    My 92 Deville was running a little rough and mileage was quite low for a long time. It finally gave me a code for a MAP sensor. It was $45 at Autozone and the mileage went up immediately. It could be a cheap gamble and it's only 2 screws.

  15. #14
    lenny lincoln is offline Cadillac Owners Fanatic
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    Re: tuning Questions for a 93 deville

    Rock and Roll. Went from 10 average around town to 16.5 with a different MAP sensor scored form the yard when I was grabbing other parts. Thanks for the tip. Now I need to find out why my power steering switch is staying open. I grabbed another one off a junker only to have the same problem. Not many of you guys has had there switches go bad so that leds me to think that theres something eles going on. Anybody have there switch go bad and throw a code.

  16. #15
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: tuning Questions for a 93 deville

    I got the code for power steering switch but I haven't replaced it yet. I read here somewhere that it can cause low idle problems too. I assume it's fairly common and I'm hoping I can just replace it with a new one.

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