1997 STS - Rough idle & Acceleration - Hard starting in cold weather
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Cadillac Seville / Cadillac Eldorado Forum Discussion, 1997 STS - Rough idle & Acceleration - Hard starting in cold weather in Past Cadillac Vehicle Discussion; I just bought a 1997 STS Seville in September, from an auction liquidator and there was only one previous owner ...
  1. #1
    STS_FirstCar_Love is offline Cadillac Owners Member
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    1997 STS - Rough idle & Acceleration - Hard starting in cold weather

    I just bought a 1997 STS Seville in September, from an auction liquidator and there was only one previous owner and from his manual and the shape of the car it was driven by an older gentleman very well taken care of and oil changes on time.

    CURRENTLY Around
    168,000Km or just under 100K Miles

    Anyways a few days after buying the car It has been having a very rough idle especially in reverse the RPM's drop from 750 to about 500 like its going die but it never dies or stalls. Now that it is colder its having a harder time starting up, I have just taken off and cleaned my EGR Valve and it hasn't helped too much.

    I did put in half a tank of 87 when I bought it not thinking, not sure if I didn't notice the rough idle when testing it out but ever since that 87 was in I noticed. Since then Ive been running 91 (Premium in canada) and more recently the last three fills Ive used Chevron 94 but I haven't noticed much of a difference.

    Ive read people having problems with spark plugs
    http://www.cadillacforums.com/forums...eleration.html

    Also another post about the EGR Valve hence me trying to fix it.

    I have zero codes that are current, only one is B1983 that was from disconnecting power to the EGR valve and starting the engine. Which the idle problem existed before those codes showed up.

    Also the AC compressor in the car is leaking or not working, I tried to charge it but nothing.

    My main concern is the rough idle & acceleration (if I open full throttle on the highway there is a smell that comes from the car for a minute or so)

    I can post a video of the idle RPM's if necessary.

    CODE DISPLAY
    https://www.youtube.com/watch?v=UEXi...e_gdata_player

    RPM PROBLEM
    https://www.youtube.com/watch?v=fxA1...e_gdata_player

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  3. #2
    vincentm's Avatar
    vincentm is offline Cadillac Owners Connoisseur
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    Re: 1997 STS Seville - Rough idle & Acceleration - Hard starting in cold weather - He

    start pulling plugs, when's the last time they were changed?

  4. #3
    STS_FirstCar_Love is offline Cadillac Owners Member
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    Re: 1997 STS Seville - Rough idle & Acceleration - Hard starting in cold weather - He

    Quote Originally Posted by vincentm View Post
    start pulling plugs, when's the last time they were changed?
    I have never changed them and I doubt the old owner did either.

  5. #4
    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
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    What kind of smell are you getting?

    The engine will run perfectly fine on 87 octane, that has nothing to do with the problem.

    For starters, it probably needs a thorough TB cleaning.

  6. #5
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 1997 STS Seville - Rough idle & Acceleration - Hard starting in cold weather - He

    Clean the TB. There is a tutorial in the Tech Tips section if you need help.

    P.S.

  7. #6
    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
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    Ah yes,

  8. #7
    STS_FirstCar_Love is offline Cadillac Owners Member
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    Re: 1997 STS Seville - Rough idle & Acceleration - Hard starting in cold weather - He

    Thank you guys for the advice, I changed 2,4,6,8 spark plugs tonight and the problem is maybe 75% gone ill change 1,3,5,7 wednesday.

    Also this is my first car, I might not know too much about mechanics but I am very smart and intuitive.

    I will also do a Throttle Body cleaning this weekend

    Once I finish the spark plugs ill post an update if the problem has stopped.

  9. #8
    N*Caddy's Avatar
    N*Caddy is offline Cadillac Owners Master
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    Re: 1997 STS Seville - Rough idle & Acceleration - Hard starting in cold weather - He

    Later in the evening when it gets dark, or inside a garage with the lights of start the car and using one of those plant sprayers (or an empty bottle of Febreze), fill it up with water and mist it over the spark plug wires (especially in the area where the wire are close to metal surfaces).
    Pay attention to small bluish sparks between the wires and the metal surfaces. If you see these then your sparkplug wires are no longer good, you will have to replace them.
    Use only AcDelco spark plugs and spark plug wire set. 100K Miles (or 160K Km) is the due date for the first engine tune up.
    Before removing the old spark plug wires pay attention to the routing (make pictures), the wires are held together with some plastic clamps, bent in a specific way and ran inside a plastic wire protector in the area where attached to the left rear engine beauty cover stud.
    You should not need to remove the coil pack or the upper strut bar. But I hear some people are doing so...whatever looks easy for you.
    You may also want to check the PCV valve, make sure if you shake it it makes a rattle. Be careful with the rubber fittings on the vacuum line, by this time are very brittle.

    The car should run on regular (87) but for best results premium (91) is recommended. Petro-Canada premium gas is what I always used with great results (by that I mean never a problem). When I am in US I just fill up from large chain gas stations with the highest-octane gasoline they have.

  10. #9
    stoveguyy is offline Cadillac Owners Connoisseur
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    Removing coil pack is easy once u find the 4 mounting bolts

  11. #10
    STS_FirstCar_Love is offline Cadillac Owners Member
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    Re: 1997 STS - Rough idle & Acceleration - Hard starting in cold weather

    Quote Originally Posted by stoveguyy View Post
    Removing coil pack is easy once u find the 4 mounting bolts
    It was easy once I removed some of the wires to the coil pack, lucky for me they are all numbered so no need to memorize anything. I'm currently as we speak in class waiting for the engine to cool down and ill replace the remaining 4 spark plugs right after.

    Also later tonight I will try that spray bottle trick N*Caddy was talking about.

    Tomorrow is TB and IAC cleaning, reading the post do you guys recommend getting electronic cleaner and not risk using carb cleaner?

  12. #11
    Ranger's Avatar
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    Re: 1997 STS - Rough idle & Acceleration - Hard starting in cold weather

    I have used Gumout carb cleaner for years (because it was on my shelf) without any problems.

    The other choice is TB cleaner.

  13. #12
    N*Caddy's Avatar
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    Re: 1997 STS - Rough idle & Acceleration - Hard starting in cold weather

    If you still have the sparkplug wires with the cylinder numbers on then you have the original wires. 16 years old wires with 160K Km, no need to do the mist test, are OVERDUE!
    New sparkplug wires from Rockauto with shipping + custom fees for Canada is roughly $140 (I don't remember exactly how much I spent few months ago). DO NOT buy anything but ACDelco even if the price difference is $100, there is a reason for that.
    Sparkplugs you mentioned are already replaced, if you did not used ACDelco start planing to change them again in the next 5000Km. I've been that route 8 years ago and I know what I am talking about. As far as I am concerned Bosch owes me $110 in sparkplugs.

  14. #13
    STS_FirstCar_Love is offline Cadillac Owners Member
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    Re: 1997 STS - Rough idle & Acceleration - Hard starting in cold weather

    I have changed all the spark plugs with non AC Delco plugs hopefully they work longer than five thousand kilometers if not I guess I will change them, the spark plug wires will be changed this week. Could they be the reason it's hard to start in the cold? My idling problem is 95 percent done with spark plug changes and probably going to disappear with a wire change. What should I test for when seeing what is causing hard start in the cold I have no codes that are current and none that are relevant.

  15. #14
    Ranger's Avatar
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    Re: 1997 STS - Rough idle & Acceleration - Hard starting in cold weather

    Wrong plugs could play a part. What did you gap them too?

  16. #15
    daslabb2k2 is offline Cadillac Owners Member
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    I had this problem eith my 97 Seville. My hard starts came from a bad fuel pressure regulater valve. When I remove the vacuum line that went to it had fuel in it which is not supposed to happen. My rough idle and acceleration car from bad spark plug wires.there is a YouTube video on how to test them to make sure ir bad before you buy new ones.

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