: Help: Car jerks to right (and tries to throw me off the road) at ~85mph



GrahamB
04-05-11, 04:26 PM
I have a 2004 V w/ 42k mi on it. This jerking issue came on all of a sudden a few months ago and I have been trying to figure out the problem. It only happens during acceleration, it only happens at between 83-87mph, and it is never on conjunction with brakes being applied. It has happened during somewhat aggressive acceleration and it has occurred during slow acceleration. When it happens the car suddenly dives to the right, the front tire locks (tire screeching), stability control pops on, and car jerks back to control. It seems like the massive jerk and stability control popping on occurs simultaneously although the first two times I could have sworn that it was an after effect of the actual jerking/screeching and didn’t pop on until after the episode began.

It does not happen every time although as far as I know the car has only gone above that threshold (and only by a few miles per hour) 2 or 3 times since this reared its ugly head. I have taken it to the dealer and they have performed their fine toothed comb over of it and found nothing wrong with it what so ever. Their ONLY solution to why it was occurring, and a solution they were 100% confident on, was that I am running 245-45-18s in the front and 275-40-18s in the rear……which frankly is a cop out answer because they didn’t have a flippin clue.


This has taken all of the fun out of the car and frankly I don’t feel safe driving it.

Thanks,

Graham

heavymetals
04-05-11, 04:54 PM
On mine it was the YAW sensor right under the center console.

Scared the crap out of me as it yanks the wheel out of your hands (just about).

Koooop
04-05-11, 10:07 PM
I can see this in about 2029.

Hello Cadillac? You got a Yaw sensor for my '05 V?

CancerJCC
04-05-11, 10:47 PM
On mine it was the YAW sensor right under the center console.

Scared the crap out of me as it yanks the wheel out of your hands (just about).

Get out of here with your YAW sensor! haha

OP the majority of us have found it to be the steering wheel position sensor or the wheel speed sensor. Heavy is the only one who had his YAW sensor manufactured by that one disgruntled assemblymen! ;)

http://www.cadillacforums.com/forums/2004-2007-cadillac-cts-v-general/181784-diy-steering-wheel-position-sensor-install.html

GrahamB
04-06-11, 12:36 AM
Thanks for the replies everyone. I am leaning towards speed sensors since I get no warning lights and the only info from the vehicle is appearance of the Stability Control on the screen. Is there any official write up (service manual?) or bulletins from Cadillac that I can reference when I take it back to the dealer? Heck even a good write-up online would be better than nothing. Given my prior experience I may have to draw them a diagram of how to fix my own dang vehicle.

Thanks again,

Graham

GrahamB
04-06-11, 10:28 AM
Just spoke with the service advisor (who of course remembered my issue) and discussed different sensor possibilities with him. He kept insisting and jumping up and down it was tire size and that tread + difference in tires size = this problem. Eventually when it was obvious that I thought he was full of S*** he told me to go get my receipt, call GM, and talk to their technical center so they can deal with me. He also stated that his tech spend "a lot of time" testing different sensors and at different speeds/accelerations including the hub bearings (which I took as them checking speed sensors).

Graham

mberisha
04-06-11, 10:36 AM
Just spoke with the service advisor (who of course remembered my issue) and discussed different sensor possibilities with him. He kept insisting and jumping up and down it was tire size and that tread + difference in tires size = this problem. Eventually when it was obvious that I thought he was full of S*** he told me to go get my receipt, call GM, and talk to their technical center so they can deal with me. He also stated that his tech spend "a lot of time" testing different sensors and at different speeds/accelerations including the hub bearings (which I took as them checking speed sensors).

Graham

Keep on them...and don't leave until you get the service.....

Most people get frustrated and walk away....that's usually what the dealers are hoping for....keep pressing them....

Fasciaguy
04-06-11, 12:30 PM
The speed sonsor sounds like a logical answer. The fact that you have two different size tires would throw the reading off. Which also explains why you have to be doing over 82 before it kicks in.
Think about this for a second. Each wheel has a speed sensor that detects even slight speed changes from the other 3 tires and kicks in the stability control to make the speed of each wheel the same right. Two different size tires may only have a diameter difference of 2 inches, so at 60 mph the speed sensor is only off maybe 2 or 3 mph but get up to 80 or in your case 82 and its off by 4 maybe 5 which is probably enough to warrant the stability control. I dont know what that threshhold is it may be the slight differences in sensors from right to left that cause it to lock up only one side. Your so close to kicking in the Stability control at 81and creaping up on it ever so slightly that it throws one side over the edge before the other. Being that each sensor probably has a tolerance range making pretty unliklely you could engage both at the exact same time makes sense to me. One side may engage just slightly before the other. In a slide condition which is what that system was designed for, those differences are reached at much slower speeds. Easy way to test it is hold your TC button down for 8 sec to shut the Stability control off (it comes up on the screen) then run it up to 85 and see if it does it still.. My guess is it wont.

612WharfAvenue
04-06-11, 04:02 PM
He's running the same size left to right though - I don't see how a f/r speed mismatch would cause stability control to turn the car. Seems like if anything it'd make TC kick in. Aren't there a ton of guys out there running different tires front and rear?

Wonder how comp mode would effect things, since it supposedly gives more leeway before intervening (maybe then it kicks in at 90 instead? not sure that I'd want to even test that myself though...)

CancerJCC
04-06-11, 04:16 PM
I don't blame the dealer buddy. If you have tires that are outside of the original specs (especially different) then you need to remedy that first. Then if it doesn't go away the dealer can move forward.

If you have ever looked at a repair .pdf that darkman often posts you will see that the GM techs have to resolve A issue and then if the problem still persists they move on to B and so on. You are making it easy but leaving them at "A". Good luck.

BTW if this isn't warranty work then tell them to replace the wheel speed sensors if your sure the tire size isn't affecting things....

Koooop
04-06-11, 08:10 PM
Tire size?

If it's just width I don't see how that could do anything to the car, there are plenty of folks here with extra wide rears on their cars.

If the height is different you could be making the computer try to compensate for wheel spin. That sounds like a possibility

I gotta ask.

Why do you run different size tires? That sounds like it would just FUBAR the handling of the car.

kevm14
04-06-11, 09:59 PM
275/40-18 is, by spec, almost dead nuts on a 245/45-18 for diameter. The 275 is literally half a millimeter shorter than the stock 245 (again, by spec). Tread, by comparison, wears in the range of 4-5mm over the life of the tire so this should be in the noise. For a practical example, take a stock set of brand new tires. Now powerslide the car around a couple corners (or do a few burnouts if you are blessed with the hop fixes). That's about the diameter difference, front to rear, that the OP would be looking at. I really hope the ABS wouldn't have a problem with that.

heavymetals
04-09-11, 07:04 PM
One other thing I forgot

Check your G meter.

Mine had readings of over 1G.

c4ss
04-10-11, 12:20 PM
Every guy I know with a V is running 275's on the rear these days. Sounds like your typical Stealership copout to avoid finding out what the problem REALLY is...

mberisha
04-10-11, 03:44 PM
Every guy I know with a V is running 275's on the rear these days. Sounds like your typical Stealership copout to avoid finding out what the problem REALLY is...

ditto....

whisler151
04-11-11, 07:43 PM
ditto....

Ditto x2.

Fasciaguy
04-14-11, 02:42 PM
I wasnt suggesting that the tire size difference was from side to side I was saying that the difference from front to back being different may cause the Stability control to kick in but that because your creeping up on the threshhold ever so slightly that you are probably kicking one side on before the other which is why its pulling to one side. However I didnt do the calculations and if its true that there is only 0.5mm difference in diameter from the 275/40 and 245/45 then I would not expect the control system to be the culprit but a speed sensor that is out of calibration.
I'm not for sure on this but lots of those sensors use magnetic pick ups and the axle has a bunch of teeth that provide the RPM signal to the magnet. If you have a couple teeth missing that would certainly throw off the reading but I would more likely lean toward a speed sensor. Just really strange how it only does it at a high speed and no other time. Most of those sensors when they go bad just stop altogether. Good luck with the dealership sounds like a hard one to track down.
Does it do it everytime you reach 82? have you tried to go over that speed with the SC shut off. That would tell you for sure if its at least a component of that system.

heavymetals
04-14-11, 03:39 PM
The "easy" way to see if it is a steering sensor is to bang on the steering column while monitoring Tech II while turning the wheel.

If defective, the #'s will jump around rather then a "smooth" transition.