Brakes Locking When Accelerating?

shinryuhoshi · December 14, 2003

Traction Control Question:

The weather is cold now and I'm driving around in my sc300 when i have to stop at a red light. As soon as the light turns green, i release my foot off the brakes and press slightly hard on the accelerator. The car begins to shake violently in place for a second, the "loss of traction" icon appears on the dash, I hear loud thumping around the rear wheels, then i finally begin to move again. It has happened twice today and my guess is that the TCS was activated and the wheels were fighting against the brake pads when i tried to accelerate. Is this theory correct? It had just rained outside but maybe the wet surface had a factor, I don't know. Is it the traction control trying to stop the tire from spinning?

Has this happened to any of you? What would cause this? What may I be damaging if i'm not careful? Thanks for any help.

Edited December 15, 2003 by shinryuhoshi

AWJ · December 15, 2003

Hard to say what the problem is for sure without being there. When you say loss of traction, I'm thinking your tires are spinning out from the road. Your car probably has traction control and it's trying to keep them from spinning out. The thumping you hear might just be the traction control in action.

If you are mechanically inclined, check your e-brake adjustment at the rear rotors. Check the rotor surfaces for damage. Aside from that or if you are not mechanical - you probably should take it in.

TallKDR · December 15, 2003

If you want some more info you should go out and personally try to make it happen again.

Sit at a stop and press on the brake HARD. all the way down. The power brakes should let you do it. Then try and take off slowly. If it happens again, well, then you know something is up.

Also, if your theory is brakes are holding. Try simply letting off the brake after you do that. The car should move forward on its own. If it doesnt, then i would say, yes theyre sticking somehow. (which is weird.. since brake pads dont actually MOVE, theyre always touching, they just provide more pressure really, with very minimal movement, i think its hard for them to stick)

shinryuhoshi · December 15, 2003

That's very possible. The ground was slick from the rain that had passed by so it could be that the tires were getting ready to spin out and the traction control stopped it before it happened. I know for sure that the tires never spun out but that thumping sound was probably the traction control doing its thing while i was at a dead stop. Still, should the car shake that violently? It felt like i was going to stall.

AWJ · December 15, 2003

No. It really shouldn't shake like that. It is hard to diagnose on line though. Good luck. It won't hurt to have a shop look at it. You might get lucky and they'll know what the problem is at least. Give everything a good look see.

shinryuhoshi · December 15, 2003

Well, I gave the "hard brake" test a try and i could not duplicate the gripe. It was definitely the traction control system. How exactly does the traction control system work mechanically? I'll feel it sometimes try to slow my tires down when i make a hard turn or try to accelerate hard after a red light on a slippery surface. I'm just hoping everytime it activates, it's not damaging the car from fighting the acceleration. I found this interesting article that has examples of different traction control systems,

http://www.epinions.com/auto-review-7C06-5...-39D517AB-prod1

Which does the SC300 have? I think it's this one:

"3. Drive train Traction Control. This system is the most expensive and it also uses the components of the Anti-lock system to monitor the wheel speed, and a computer that controls slippage by controlling the torque to the slipping wheel or wheels. The computer controls the torque by closing the throttle, shutting off the fuel, !Removed! the timing or shut down cylinders. The computer can use one or all of the control techniques.

One draw back is that the system controls the torque in all slippery conditions, a system cutoff switch is installed when a wheel spin is needed, such as rocking a car to get out of a hole. You will also notice that you can not accelerate through a turn, the accelerator is all the way to the floor but you are not gaining speed. This can occur even if you are not on a slippery surface.

The Traction Control systems are very useful in rainy or icy conditions. The Drive train Traction Control can be a nuisance if you are not driving in adverse road conditions. As in every system the driver still controls the vehicle, it will not make you a better driver but gives you more control of you vehicle when you encounter adverse weather conditions. As always drive safe, and drive defensively."

sightdev · December 15, 2003

If you have working TRAC on your SC you should not feel a thing when it engages. Only notice is the amble light TRAC come on in the middle of the panel and drop in your RPM. Thumping is probably from your tire spinning on rough surface which can be caused by violent movement that can’t be subdue because of bad tires, shocks or both. IMO your TRAC is not working and your shocks are shot.

shinryuhoshi · December 15, 2003

If you have working TRAC on your SC you should not feel a thing when it engages. Only notice is the amble light TRAC come on in the middle of the panel and drop in your RPM. Thumping is probably from your tire spinning on rough surface which can be caused by violent movement that can’t be subdue because of bad tires, shocks or both. IMO your TRAC is not working and your shocks are shot.

When I'm at high speeds and the TCS engages, i won't feel it. I'll only feel it during hard accelerations from a stop(on wet surfaces) and trying to accelerate during a turn. I think i found my answer on this previous thread...

http://us.lexusownersclub.com/forums/index...=ST&f=7&t=4699&

That sounds right, fuel is cut off and the engine wants to shut off, causing the stall-vibration. :huh: