Last post on Jul 01, 2013 at 5:50 PM
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Cadillac DTS, Automotive News, Sedan
#337 of 896 Re: 2006 Cadillac DTS III downhill inadvertent acceleration problem. [wpsr]
Sep 23, 2006 (11:54 am)
My 2002 Seville shuts off the fuel injection system when coasting downhill, but there is no surge when the system comes back online.
The recommended minimum pressure is on the door post. The maximum inflation pressure designed for the tires is on the tires. The softest ride will come from using the door post pressure. A few extra pounds of pressure will not hurt anything, but the tire pressure monitor (I don't have one) may object to too much pressure. One should check the tire pressures on a regular basis.
#338 of 896 Re: 2006 Cadillac DTS III downhill inadvertent acceleration problem. [sls002]
Sep 23, 2006 (1:14 pm)
Difficult to know why Cadillac will not fix the surge. 600 to 700 rpms is way too much and makes using the brakes continuously necessary. True on the pressure, you cannot use more than about 33 in the summer. I doubt if they will wear very good at 30, we will see.
#339 of 896 Re: 2006 Cadillac DTS III downhill inadvertent acceleration problem. [wpsr]
Sep 24, 2006 (8:09 am)
If your dealer's service department can't fix the problem, you should talk directly with Cadillac and keep after them until you are happy. Remind them of the problems with Audis doing something similar around 1990.
#340 of 896 Re: foot off gas and rpms don't drop. car keeps going [buckeyedad]
Sep 25, 2006 (6:20 am)
I tested our 06 DTS III yesterday (all on flat highway), at 65 with the cruise on it does not drop more than 50 rpms when I hit the brake to kick off the cruise. We bought this one in March 06. It takes a long time for it to slow down. It appears the throttle is not returning to the idle position. If the throttle returned to the idle position it sure would drop more than 50 rpms on flat ground. I have never been a brake driver, this car takes a lot of braking. (be extremely careful if you try this, if you hit reverse you might leave a big pile of metal on the freeway) This was weird, at around 55, if you kick the car into neutral it will not idle either. When we are coming down a long downhill grade we have to take the car out of drive to get it to slow down. It is like a run-away-horse. I will talk to the dealer this week, the car is ready for service anyway. No one has solved our low gear downhill acceleration problem. We have contacted Cadillac, with no results. wpsr
#341 of 896 Re: foot off gas and rpms don't drop. car keeps going [wpsr]
Sep 25, 2006 (8:52 am)
On long down hill grades you should put the transmission into 3rd gear for engine braking. This will work at speeds above 40 MPH. If you need engine braking at speeds of 35 MPH or less, then 2nd gear may be needed.
As I pointed out above, when the torque converter is locked up, the engine is connected directly to the wheels and the RPMs will not drop when the cruise control is disengaged. However, I think that a second tap on the brakes should unlock the torque converter, but this is something to query the service manager about. This may be the whole problem in fact.
My Seville has a console mounted gear shift, which makes shifting much easier. I am looking forward to the tap up/down shifters that GM seems to be introducing with the six speed automatics.
#342 of 896 Re: foot off gas and rpms don't drop. car keeps going [sls002]
Sep 25, 2006 (11:37 am)
It does not matter what you do, including tap the brakes more than once. The rpms do not drop. When we find it necessary to shift to 2nd or 1st , that is when we get our famous 600 to 700 rpm surge, dangerous. Cadillac nor the dealer will fix it. buckeyedad has it right! wpsr
#343 of 896 Re: foot off gas and rpms don't drop. car keeps going [wpsr]
Sep 26, 2006 (6:16 am)
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.
#344 of 896 Re: foot off gas and rpms don't drop. car keeps going [sls002]
Sep 26, 2006 (11:52 am)
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
#345 of 896 Re: foot off gas and rpms don't drop. car keeps going [wpsr]
Sep 27, 2006 (6:23 am)
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?
Sep 27, 2006 (8:03 am)
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...