93 sts
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Northstar Engines and System Technical Discussion Discussion, 93 sts in Cadillac Engine Technical Discussion; hi guys my 93 sts 116 k miles goes like stink but i have noticed when i cane it it ...
  1. #1
    silver duke is offline Cadillac Owners Member
    Automobile(s): 93 cadillac sts seville
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    93 sts

    hi guys my 93 sts 116 k miles goes like stink but i have noticed when i cane it it makes a rotten egg smell. i have already cleaned the throttle body and replaced the air filter and pcv. car runs great though. i love this car i have only had it a few weeks already considering purcasing another. but we are caddy guys in my family the 93 is the 4th caddy in my family. i am going to learn the northstar inside out motor swaps ,the whole 9. what do you guys think makes the smell? i am leaning to the o2 sensors are they 4 wire sensors or the 1 wires?

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  3. #2
    growe3's Avatar
    growe3 is offline Cadillac Owners Enthusiast
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    Re: 93 sts

    The rotten egg smell is from either a rotten egg , someone left hidden in the car, or more likely a bad catalytic converter.
    Catalytic Converters can be ruined from various fuel additives used in the past, and/or from too rich of a fuel mixture (causing the CC to run very hot). A rich fuel mixture can also be commonly from a leaking Fuel Pressure Regulator. This condition can be hard on the 02 sensors that may also not be working correctly.
    Safety First:
    To access the FPR you will need to remove the intake cover.
    Never start a 93-94 Northstar with the top of the intake removed!
    With the top of the intake removed you have no throttle control. The engine will run wide open and may rapidly destroy itself or cause serious engine damage. The top of the 93-94 intake manifold is not a decorative piece to just take off, as in later models. It is the "cap" of the intake plenum. Removing and replacing the top unnecessarily will start to compromise the gasket of the Fuel Rail and will lead to poor sealing, idle and drivability problems.
    The oily residue in the bottom of the intake is normal and it is not necessary to sop it up; it will just come back. It is from crankcase and gas vapors settling out.
    The Torx screws on the 93-93 intakes are special; in a strong backfire it will allow the intake cover to lift slightly against the rubber isolator pieces on the screws, to relieve pressure, rather than burst the intake manifold. If you lose one replace it with the correct screw and isolator combination from the dealer.
    Unless you are really inspecting for a fuel injector or FPR problem, you should not remove the 93-94 intake cover.
    To check the FPR:
    Unplug the (4) coil wire plugs at both ends of the coil pack for safety. If the engine starts with the cover off it will runaway; due to uncontrolled air intake.
    Pull off the front spark plug boots.
    Lift the plastic sparkplug wire carrier from the intake and shift out of the way.
    Remove the magnesium intake cover (all of the Torx screws, not the 4 hex head screws). Turn the key to the ON position and look for seepage from the nipple, on top of the FPR. Any fuel coming out of the FPR nipple, and it needs to be replaced.
    To replace the FPR you will need to lift the fuel rail out of the way. Exercise care or the fuel rail will break.
    Replace plastic sparkplug wire carrier, and plug the spark plug boots back in.
    After replacing the intake cover be sure to plug the (4) coil wire harness plugs back in.
    To check the 02 sensors:
    Start the engine and allow to completely warm up.
    Enter the diagnostics mode and review the DATA for the 02 sensors. The voltage readout should vary from 0-1.16 volts. The value should vary frequently; a slow or not changing value means that the sensor is not working correctly.
    PD32 Front 02 sensor
    PD33 Rear 02 sensor
    Front sensor is easy to replace, rear is hard.
    -George
    Attached Images

  4. #3
    silver duke is offline Cadillac Owners Member
    Automobile(s): 93 cadillac sts seville
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    Re: 93 sts

    thanks very much for the advice and instructions,i will start with the o2 sensor check. are there any drivability problems associated with the fuel press regulator? the car runs and drives great , good idle, aside from the smell at wot or high rpm ? could i possibly test the fuel pressure? is there any schraeder valve ? i already own a fp test guage.

  5. #4
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 93 sts

    Yes there is a schreader valve on the fuel rail for testing the fuel pressure.

  6. #5
    growe3's Avatar
    growe3 is offline Cadillac Owners Enthusiast
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    Re: 93 sts

    Quote Originally Posted by silver duke
    thanks very much for the advice and instructions,i will start with the o2 sensor check. are there any drivability problems associated with the fuel press regulator? the car runs and drives great , good idle, aside from the smell at wot or high rpm ? could i possibly test the fuel pressure? is there any schraeder valve ? i already own a fp test guage.
    Unless the pressure is low you won't likely notice a problem. If it is leaking you will get a little bit of a rough idle and elevated emission levels. The FPR maybe leaking fuel into the engine when it is off, which causes an over rich condition when the engine is started. This is a likely the cause of the rotten egg smell. With the over rich problem fixed the smell MAY go away.

    Fuel pressure is easy to test. Standing on the driver's side of the car, looking at the engine, the Schrader valve is located just under the brake lines coming from the master cylinder.

    Fuel pressure should be about 42 PSI at idle and increase to about 45+ PSI when accelerating. Below 40 PSI is a problem (fuel pump is probably failing), above 50 PSI and the FPR is failing or the return line may be blocked/kinked.

    If you decide to replace the Catalytic Converter, don't cheap out. Be sure to get one designed to work for the Northstar. It is a very efficient unit and flows extremely well.

    -George

  7. #6
    growe3's Avatar
    growe3 is offline Cadillac Owners Enthusiast
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    Re: 93 sts

    I just noticed in my posts that some words are being Double Underlined. This is apparently being done by something on the Cadillac website. It is a hyperlink created to parts vender(s).

    I do not know where these ads come from, or encourage you to buy from these "unknown to me" vendors.

    These ad links are being created without my knowledge or approval!

    -George

  8. #7
    silver duke is offline Cadillac Owners Member
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    Re: 93 sts

    thanks very much for the help george

  9. #8
    mcowden is offline Cadillac Owners Connoisseur
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    Re: 93 sts

    Quote Originally Posted by growe3
    The rotten egg smell is from either a rotten egg , someone left hidden in the car, or more likely a bad catalytic converter.
    Catalytic Converters can be ruined from various fuel additives used in the past, and/or from too rich of a fuel mixture (causing the CC to run very hot). A rich fuel mixture can also be commonly from a leaking Fuel Pressure Regulator. This condition can be hard on the 02 sensors that may also not be working correctly.
    Safety First:
    To access the FPR you will need to remove the intake cover.
    Never start a 93-94 Northstar with the top of the intake removed!
    With the top of the intake removed you have no throttle control. The engine will run wide open and may rapidly destroy itself or cause serious engine damage. The top of the 93-94 intake manifold is not a decorative piece to just take off, as in later models. It is the "cap" of the intake plenum. Removing and replacing the top unnecessarily will start to compromise the gasket of the Fuel Rail and will lead to poor sealing, idle and drivability problems.
    The oily residue in the bottom of the intake is normal and it is not necessary to sop it up; it will just come back. It is from crankcase and gas vapors settling out.
    The Torx screws on the 93-93 intakes are special; in a strong backfire it will allow the intake cover to lift slightly against the rubber isolator pieces on the screws, to relieve pressure, rather than burst the intake manifold. If you lose one replace it with the correct screw and isolator combination from the dealer.
    Unless you are really inspecting for a fuel injector or FPR problem, you should not remove the 93-94 intake cover.
    To check the FPR:
    Unplug the (4) coil wire plugs at both ends of the coil pack for safety. If the engine starts with the cover off it will runaway; due to uncontrolled air intake.
    Pull off the front spark plug boots.
    Lift the plastic sparkplug wire carrier from the intake and shift out of the way.
    Remove the magnesium intake cover (all of the Torx screws, not the 4 hex head screws). Turn the key to the ON position and look for seepage from the nipple, on top of the FPR. Any fuel coming out of the FPR nipple, and it needs to be replaced.
    To replace the FPR you will need to lift the fuel rail out of the way. Exercise care or the fuel rail will break.
    Replace plastic sparkplug wire carrier, and plug the spark plug boots back in.
    After replacing the intake cover be sure to plug the (4) coil wire harness plugs back in.
    To check the 02 sensors:
    Start the engine and allow to completely warm up.
    Enter the diagnostics mode and review the DATA for the 02 sensors. The voltage readout should vary from 0-1.16 volts. The value should vary frequently; a slow or not changing value means that the sensor is not working correctly.
    PD32 Front 02 sensor
    PD33 Rear 02 sensor
    Front sensor is easy to replace, rear is hard.
    -George

    Hey George - haven't seen ya around for a while. Nice to have you back.
    Mike

  10. #9
    dkozloski's Avatar
    dkozloski is offline Cadillac Owners 10000+ Posts
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    Re: 93 sts

    If you click on the double underlined words you get to a window where you can turn the damn thing off.

  11. #10
    growe3's Avatar
    growe3 is offline Cadillac Owners Enthusiast
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    Re: 93 sts

    Hi Michael,
    I have been pretty busy the last couple of months. Working on our vacation home in MI, at work I am doing drafting and design on the biggest building/lab we have ever designed, and at home I had to do some rebuilding on the 454' in my Suburban. By the time I stop for the day I am worn out.

    -George

  12. #11
    growe3's Avatar
    growe3 is offline Cadillac Owners Enthusiast
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    Re: 93 sts

    Quote Originally Posted by dkozloski
    If you click on the double underlined words you get to a window where you can turn the damn thing off.
    Ya, I found the link and turned off the ads in both FireFox and IExplorer.

    What bothers me is:
    1. This type of misleading advertising, if it is placed in my response, a reader would likely think that I endorse the product, and that I am recommending that they it to buy to fix their problem.

    2. The obvious scams. They are still trying to get you to buy magnets to improve the gas mileage. Shameful advertising.

    3. I am completely against this type of advertising, I feel it crosses the border of ethical use of electronic gimmicks and "snake oil" advertising. Using your message post, to try and sell things, without your knowledge or approval.

    I have expressed my concerns about this type of advertising to Sal, and would encourage others to do the same.

    -George

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