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Cadillac DTS



  • sls002sls002 Posts: 2,788
    When you down shift to a lower gear the engine's speed WILL increase, that is NOT a surge.

    Your axle ratio is 3.11:1 unless you have the high performance model. In 3rd gear your engine should run about 2000 RPMs at 50 MPH. What this means in terms of other gears is:
    4th gear - 0.68:1 -> 1360 RPMs (torque converter locked - otherwise faster)
    2nd gear - 1.63:1 -> 3260 RPMs
    1st gear - 2.96:1 -> 5920 RPMs

    I would have thought that any competent person would realize that a lower gear will speed up the engine.
  • wpsrwpsr Posts: 21
    I must not have explained the problem very well. Please read message 336. If I can help with more information I will try. I took the car for service today, no help on any of the problems. My only intention is to solve these problems without insulting or offending anyone. I am adding # 5 to my list.

    5. When using the cruise control on a flat highway for example at 65 mph, when you hit the brake and stop the cruise control, the rpms drop only about 50 rpms. It does not matter how many times you hit the brake peddle to kick off the cruise. The throttle is not returning to idle when you kick off the cruise control. Even in 3rd gear the throttle does not seem to return to idle when you let your foot off the gas. The car takes forever to slow down. wpsr
  • sls002sls002 Posts: 2,788
    In your post #342 you state the the "surge" happens when you shift down. This is normal.

    As I explained in some detail, when your in gear the engine is connected to the wheels and if they are turning your engine will also have to turn. The torque converter will act as a fluid coupling or clutch and at speed will force the engine to spin. At low speeds the torque converter will begin to "slush" and will let the engine run at idle speeds.

    If you check the instantanous MPG, you should see some difference between the MPGs when the cruise is engaged at 65 MPH, and after you touch the brake, disengaging the cruise, the instant MPGs should jump up to 70 MPG or so. If it does, then the fuel injectors have shut down. If the fuel consumption remains constant, then there is something wrong -> perhaps your throttle body is sticky?
  • marsha7marsha7 Posts: 3,666
    When you see 30 psi on the door sticker, but 44 on the tire, it should mean that the max safe tire pressure for the TIRE is 44 psi (hot or cold, I wonder?)...the 30 on the door sticker is Caddy telling you that the car was engineered to run any tire at 30 psi COLD...because of the gap between 30 and 44, you can actually inflate your tires to about 32-35 cold, depending on the ride you like, still be within safe limits, and allow for a few psi leakage and still be at 30 psi cold...

    My Crown Vic calls for 35 psi on the sticker, 44 psi max on the tire, I inflate it to 37-38 psi cold, slightly firmer ride, well within safe limits, and can leak out 2-3 psi and still be at 35 psi...:):):):):)
  • This is in response to your post #335.

    Regarding your bullet #2:
    A tire pressure of 30 PSI is for normal loads and speeds. Maximum PSI of 38 (not the 44 on the tire side) is for higher speeds (100 MPH). This is all explained in the owner’s manual in the tire section on page 5-58. The page number is dependent on the manufacture date of the vehicle. Setting your tires at a cold pressure higher then recommended can set off the alarm warning as the tires warm up – I set mine at 32 PSI even though the label indicates 30 PSI and have not experienced any alarms yet. The higher pressure will also cause the vehicle to roll easier (less resistance) when you take your foot off the gas. This may be related to your bullet #1.

    Regarding your bullet #3:
    The rain sense wipers may come on as you described – see page 3-14 of the manual for an explanation.

    Regarding your bullet #4:
    If you only hear this noise when you accelerate – see my posting #308.

    Good luck – hope this helps.
  • This is not true - read the manual. All recommended pressure are for COLD tires. And it does not refer to any tires - only tires that have IDENTICAL SPECIFICATIONS. Tires are very much different even though they are the same size. I keep mine at 32 instead of the 30 PSI recommendation. The manual (page5-58) recommends 38PSI for 100 MPH speeds and not the 44PSI on the tire wall.
  • wpsrwpsr Posts: 21
    I was referring to #336. The statement you mention is misleading by itself. This is with the trans in 1st at around 15 mph coming down a fairly steep hill, like where we come to our home. It happens on other similar roads around town. The dealer has had the car for testing two times for several days. This engine revs up 600 to 700 rpms when this happens and you surge or speedup while going downhill with your foot on the brake. It is in the computer program to save gas, so the computer shuts off the gas when the car is pushing the engine for a short time. It slows down great until the surge. When the engine slows to about 1000 rpms, then comes the surge. When the gas comes back on to prevent the engine from dieing the rpms go up 600 to 700 rpms. The engine has a lot of power and you really notice the surge. The technician was able to reproduce the surging problem. This a built in computer function to save gas as explained to us by the dealer’s head technician. The technician said that the company has no repair for this car at this time. Unless there is a computer update, there is nothing to be done. If you are going down a grade you have to put on the brakes continuously to keep the speed down. It happens about every 200 or 300 feet as you come down the grade. This situation becomes dangerous while going around the windy down hill grades in hilly country like where we live. Right as we turn into our drive way this happens almost every time. It happens even with your foot on the brake. It is dangerous!
  • wpsrwpsr Posts: 21
    The max tire pressure is 30 on the door post, 44 lbs. on the tires. All pressures are stated cold. The pressure does go up quite a lot with the hot weather. During the hot weather the pressure has gone up from 35 where I had it and the computer continuously flashes and makes noises. I lowered the pressure to 33 and it seems better, it quit flashing amd making noises. We can not put more than 33 in the hot weather, the computer flashes and beeps, it will drive you nutter than usual for me. For me, I could do without the sensors, the tires get checked about every 30 days.
  • wpsrwpsr Posts: 21
    #2 - You cannot run the pressure more than about 33 here during the hot weather. The computer will drive you nuts. We have just a little too much computer control!

    #4 - The noise only happens at 70 or 75, it sounds like plastic vibrating and I think that is what the problem is. There is plastic on either side of the hood latch. I glued it down and think it solved the problem. The dealer yesterday said they never heard of this problem. I see other people talking about it.

    Thank you, wpsr
  • wpsrwpsr Posts: 21
    I forgot to mention, the instant MPG will tell me a lot. They have tested the car and say it is OK. Thanks, wpsr
  • sls002sls002 Posts: 2,788
    OK, I understand that when your engine slows down to 1000 RPMs with the fuel shut off, the computer begins the fuel flow and the engine surges. My 2002 Seville does much the same thing, except that when the fuel flow starts, there is no surge. Generally, the instant MPGs go from 70 MPG to 69 MPG (just a tiny bit of fuel). I think that you must take this up with the Cadillac factory reps at the 800 number in your owners manual. Tell them you want a fix or you will purse the lemon law. Also tell the sales person who sold you the car that either it is fixed or the lemon law.

    Your powertrain is not much different than mine, there is no reason for a surge.
  • marsha7marsha7 Posts: 3,666
    I hope my post did not imply EVER that 44 psi was a usable pressure...I tried to communicate that it was the max safe pressure for the tire, per the manufacturer, but not that it should be used by anyone...did my post imply that???

    I meant that if the carmaker sticker reco 30 psi cold, one could add 3-5 psi anytime and not be overinflated, that's all...if the maker manual says 38 psi for over 100 mph, then, by all means, do it, but I think it is a rare one who often exceeds 100 mph...then again, there is Texas and Montana...:):):):)
  • wpsrwpsr Posts: 21
    No problem, it is just the computer on the 2006 DTS does all kinds of flashing when you go over about 33 in the hot weather. The pressure does go up a lot on a hot day. I can look at the computer and see what it is. It was up around 38 when all the flashing was going on. The biggest benefit for me is to let me know if a tire is going flat. My main concern is tire ware and safety. We had an Oldsmobile Aurora, the tires wore best at 44 lbs., that was the max on the tire. Most highways in Calif. are 65 mph.
  • sls002sls002 Posts: 2,788
    Tire pressure depends on the temperature. If you test the pressure when the tire is cold (say at 70 degrees F), and then the outside temperature increases to 90 F, your tire pressure should increase by about 1 lb. However, after driving about 10 miles, your tires will be hot, and the pressure will increase by another 4 lbs or so. So, if you set your pressure at 30 lbs when they are at 70 degrees F, after driving a while in 90 degree heat, your tires should be around 35 lbs or so.
  • sls002sls002 Posts: 2,788
    Montana's speed limit is now 75 on interstates, less otherwise. They no longer have a "reasonable and prudent" limit.
  • sls002sls002 Posts: 2,788
    One thing that you might try if you are using regular gas or some generic brand like Walmart - try using a brand name premium for at least two full tanks. By brand name I mean BP (British Petroleum or the old Amoco), Shell, Mobil, Chevron...

    I don't know that it will make a difference, but try it and see if there is a difference by the end of the second tank.
  • marsha7marsha7 Posts: 3,666
    any experience with tire pressure monitors, as I have not owned a car that had them...I did not realize that if the carmaker sets 30 psi cold as the "proper" psi, then putting 33-35 psi cold might "set off" the TPM...might even be a drawback to the TPM, since most of us aficianados know enough to check out tire pressure regularly, and I don't mean "every Christmas"...:):):)...I do not wish to appear anal retentive, but I check my tire pressure on the 1st and 15th of every month...wife gets paid, tires get checked...what could be easier???...:):):)

    I guess the TPM is esp good for telling you you have a slow or fast tire leak, acting as a warning for low psi rather than high psi, altho since we read about some repair shops putting 45-50 psi in tires, maybe having a top end warning isn't so bad...hey, maybe the "red flag" limit is adjustable, so I could set it at, say, 7-8 psi over where I keep them inflated...
  • The 2007 DTS is a carbon copy of the 2006 as far as I can see. Does anyone have any idea or heard any rumours as to when the body will change? It is still essentially the 2000 body with changes to the front and rear.
  • ehaaseehaase Posts: 328
    The DTS will probably use the same body until 2011 or 2012, when it will probably move to either the RWD Sigma or Zeta platforms.
  • wpsrwpsr Posts: 21
    We have been hearing a weird noise. It sounds as if it is coming from some part of the front of the car, at around 70 mph. There is no message being displayed. It is a buzzing sound and it comes and goes. I tried opening and closing the sun roof. This did not seem to make any difference.

    We took the car in for service the other day. The master technician had not heard of the weird noise. I think I have fixed it. We have had the car up to around 75 several times since fixing the plastic. Raise the hood, there is a latch below on the vehicle. On both side of the latch there is plastic. This plastic is vibrating at higher speeds causing the sound. I used silicone sealer under the leading edge of this plastic to glue it down. If this plastic ever needs to be removed it should come off without too much of a problem. Apparently this plastic is not loose on all of these vehicles, not everyone is hearing this noise.

    The noise in the trunk:
    I have seen several complaints on another forum, these vehicles have a vacuum pump in the trunk. If the intake vacuum in the engine becomes low this pump will run to bring vacuum to a proper amount. If the pump is running excessively you could have a vacuum leak. It is common to hear this pump right after you start the engine and it is at idle, also if you stop with the transmission in gear and the engine running at idle. If this pump is loose it could be radiating the noise, it is a small vacuum pump.
    Still no fix for the acceleration problem, see 2006 Cadillac DTS downhill inadvertent acceleration problem.
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