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#336 of 896 2006 Cadillac DTS III downhill inadvertent acceleration problem.
Sep 22, 2006 (7:25 pm)
Mileage about 4100.
2006 Cadillac DTS III downhill inadvertent acceleration problem. The car is new.
Has anyone had this problem?
This is a great car but it has some real quirks.
1. We live in hilly country. When going down hill the car will accelerate with your foot off the gas pedal about every 100 yards depending on the grade. This is especially bad on the turns. You do not expect a car to accelerate with your foot off the gas peddle on a turn or any other time. This is a safety issue. It takes excessive use of the brakes to keep the speed down and drive in a safe manor. When going down a grade we shift the car into a lower gear. The speed limit in town and the residential areas here is mostly 25 to 35 mph and in town the car should not even be in drive. The only time in town that it goes into drive is when you let off the gas peddle. This causes the car to coast excessively. We run the car mostly in 3rd gear 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 dealerís 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. 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!
The cure for this is as I understand it from the technician and one of the owners at the dealer is to always drive in overdrive and use the brake instead of shifting down. This was their recommendation.
We have contacted Cadillac and they tell us there is no fix for this problem.
We contacted NTSB on May 1, 2006. They have not contacted us.
The acceleration problem is a safety issue the others are irritating.
2. The max tire pressure is 30 on the door post, 44 lbs. on the tires. During the hot weather the pressure has gone up and the computer continuously flashes and makes noises. I lowered the pressure and it seems better.
3. The windshield wipers will run with the window completely dry, be sure not to leave the wipers on auto!
4. We are hearing a weird noise. It sounds as if it is coming from some part of the front of the car, also at around 70 mph. Other people are reporting is noise. 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 will be contacting the dealer to see if they have any answers. I may have solved this one, I am not sure yet.
These problems take the fun out of driving this car!!
#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?