2000 Deville P0300 code
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, 2000 Deville P0300 code in Past Cadillac Vehicle Discussion; Hello guys, I started my car today and noticed that it didn't sound like it normally does. I drove it ...
  1. #1
    UnkleElroy is offline Cadillac Owners Member
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    2000 Deville P0300 code

    Hello guys,

    I started my car today and noticed that it didn't sound like it normally does. I drove it about a mile or so down the road to see if it drove the same and sure enough it didn't. I got back home to check the codes and there was only one current code which was the P0300 code. It wasn't specific to the cylinders so I'm hoping it's nothing too major. Any help will be appreciated.

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
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    Re: 2000 Cadillac Deville P0300 code

    If there's a "miss" it will eventually set a SES light - steady means "miss detected"; flashing means "severe miss detected". Could be anything from a bad ignition cassette coil to ignition trigger signal to sticky injector to fouled spark plug. (A nagging miss - especially a severe miss - will cost you a catalytic converter)

    Last spark plug change ??? Last time you ran a 20 oz. jug of Chevron TECHRON through the gas tank ??? Have you ever pulled the ignition cassettes and checked the plugs and boots ?

    Unfortunately, our onboard scanners won't read out the specific cylinder number that is experiencing the miss - but a large parts store will do a free scan and their equipment will show something like "P 0302" or P 0307", where the last digit is the offending cylinder. Then YOU start troubleshooting according to all the procedures posted in these forums.

  4. #3
    basscatt's Avatar
    basscatt is offline Cadillac Owners 10000+ Posts
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    Re: 2000 Cadillac Deville P0300 code

    Quote Originally Posted by UnkleElroy View Post
    Hello guys,

    I started my car today and noticed that it didn't sound like it normally does. I drove it about a mile or so down the road to see if it drove the same and sure enough it didn't. I got back home to check the codes and there was only one current code which was the P0300 code. It wasn't specific to the cylinders so I'm hoping it's nothing too major. Any help will be appreciated.
    ---------------------
    P0300 is a generic misfire code -
    our on-board code readers will not display WHICH cylinder/cylinders is/are misfiring -
    only that there IS a misfire -

    take the car to any large auto parts store - they will check your codes for free -

    P0301 is a misfire in cylinder #1 - P0302 is cylinder #2 - P0303 is #3 - etc -

    once you discover WHICH cylinder is misfiring - diagnosis becomes much easier -

    --------------------

    damn - Sub beat me -

  5. #4
    UnkleElroy is offline Cadillac Owners Member
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    Re: 2000 Cadillac Deville P0300 code

    Thanks guys for the information. Actually I think it was an issue with bad gas or something. My mechanic looked everything over and didn't find a problem. I ran a thing of Lucas in the tank and filled up.

  6. #5
    UnkleElroy is offline Cadillac Owners Member
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    Re: 2000 Deville P0300 code

    Hey guys I'm back. Turns out that it wasn't just bad gas. I took my vehicle to another shop today because it started doing the same thing with the same
    code displaying in the on dash computer. After the mechanic looked thoroughly he cam back and told me that the miss was coming from 3 and 4. I asked
    what that meant he said until I further diagnose I don't know. He told me it could either one of the following: Bad spark plug and boot, bad coil packs, and or a blown head gasket. I was thinking a blown head gasket would have given me some other signs before it just goes bad. What do you all think? Is this mechanic in the right ball park with his diagnosis? And what is the ball park figure for the worst case scenario of the blown head gasket. Please help me I don't want to be cheated.

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    Ranger's Avatar
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    Re: 2000 Deville P0300 code

    HG is unlikely, especially both at the same time. I'd replace the plugs. It also unlikely (though anything is possible) that a coil in each ignition cassette would fail at the same time.

  8. #7
    basscatt's Avatar
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    Re: 2000 Deville P0300 code

    Quote Originally Posted by UnkleElroy View Post
    Hey guys I'm back. Turns out that it wasn't just bad gas. I took my vehicle to another shop today because it started doing the same thing with the same
    code displaying in the on dash computer. After the mechanic looked thoroughly he cam back and told me that the miss was coming from 3 and 4. I asked
    what that meant he said until I further diagnose I don't know. He told me it could either one of the following: Bad spark plug and boot, bad coil packs, and or a blown head gasket. I was thinking a blown head gasket would have given me some other signs before it just goes bad. What do you all think? Is this mechanic in the right ball park with his diagnosis? And what is the ball park figure for the worst case scenario of the blown head gasket. Please help me I don't want to be cheated.
    -----------------------
    Hey guys I'm back. Turns out that it wasn't just bad gas
    no surprise there -

    the miss was coming from 3 and 4
    I would ask for conformation -
    if that is true - you should have codes P0303 and P0304 -

    next -
    you need to determine whether the problem is ignition related - or fuel related -

    He told me it could either one of the following:
    Bad spark plug and boot,
    bad coil packs, and
    or a blown head gasket


    a misfire isn't always ignition related -
    a bad fuel injector will "kill" a cylinder just as "dead" -
    as no spark -

    And what is the ball park figure
    for the worst case scenario of the blown head gasket


    BALL-PARK-ESTIMATES are worse than useless -

    1) you can't buy a ball-park -
    2) they mean NOTHING -
    3) they serve no purpose - except to ruin your entire night -

    want proof?

    OK - a BALL-PARK figure for a blown head gasket on your car - $5000 -

  9. #8
    UnkleElroy is offline Cadillac Owners Member
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    Re: 2000 Deville P0300 code

    Thanks guys for all the insight with this issue.

    I have the final diagnosis from my current mechanic. He stated that the sole problem doesn't lie in the motor itself. He stated to me today that because of a leak in my radiator and leak in the housing of the water pump the coolant is catching the wind when I drive and blowing onto one of the belts which then is blowing into cylinder 3 and 4. It doesn't make sense to me but he said when he took the plug and boot out cylinder 3 it was drenched with coolant which was the cause of the misfire and loss of power. I know a little about cars but not enough to understand this logic that the mechanic was telling me today. Please help me with this situation. Is this even possible or do you think this guy is trying to get over on me? To top it off he stated the final bill will be close to $1000.00 and this is just to replace the radiator, water pump and housing, coolant, and he said I should go ahead and get a new thermostat as well. Parts and coolant are only about 425 bucks and the rest is labor. He said it would take 6 labor hours at $80.00 per hour. I'm thinking before I shell out that kind of cash I should get a second opinion. Please weigh in on this guys. All your help is greatly appreciated.

  10. #9
    Tom's Caddy's Avatar
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    Re: 2000 Deville P0300 code

    Please before you spend any money take it to a Cadillac dealer have them do a simple block test on it. I would not go back to you're guy.

  11. #10
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    Re: 2000 Deville P0300 code

    Even a bad radiator/water pump would have a very, very hard time "blowing coolant into #3" because #3 is in front of the passenger's left toes. Maybe a hole in the radiator/top hose would get to #4, but that's MOST unlikely.

    (Your 2000 has no external coils, so leave that out of the diagram....................)

  12. #11
    reppinshadyvill is offline Cadillac Owners Fanatic
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    Re: 2000 Deville P0300 code

    That sounds like a load of BS! You have a hole in the radiator AND your water pump housing? If you were leaking coolant, you would notice your coolant levels falling. Period. If you were burning coolant, you would notice a change in your exhaust. Lots of white smoke. It sounds like this mechanic is using your lack of knowledge against you. You need to find a mechanic you can trust and take your car there if you can't diagnose it yourself.

  13. #12
    UnkleElroy is offline Cadillac Owners Member
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    Re: 2000 Deville P0300 code

    Thanks again you guys I appreciate the knowlege that you have shared with me.

    I thought it was a load of BS myself that's why I've been asking several people about it. I questioned wouldn't everything under the hood be soaking wet and not just bank 3 and 4? That's when he said well the belt is picking up the coolant and blowing it there specifically. I have noticed a slight decrease in my coolant levels but not enough to equate to what they are saying. One quick question before I go pick it up tomorrow. Will it be ok to drive from this current mechanics shop to the dealership with it leaking and with the loss of power? In other words, before I leave I will make sure it's full of coolant and drive to the dealership but will this cause any other damage? It's probably about a 20 mile difference from point A to point B.

  14. #13
    Ranger's Avatar
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    Re: 2000 Deville P0300 code

    Probably too late, but no, it won't cause any other damage.

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