Truck Lunges

Title sounds stupid, but it mostly describes what my truck does... I have a 2017 DCSB Sport 4x4, in the morning when I start her up to go to work, after putting her in drive she seems to lunge forward when i come to a stop. Picture yourself stopped behind another car at a stop light and your engine RPM increases by 500, the amount of pressure you have applied to the brakes is now too little so it creeps forward a little.

It does this primarily when she hasn't warmed up to temp on cold days/mornings, it'll do this intermittently before soemthing makes it stop... It'll raise the RPM's by 500 for about 2/3 seconds then stop, then cycle again. This only happens when I am in drive and and when its cold... Anyone wanna chip in with brainstorming a reason for this?

 

Something with the transmission? Like fluid level perhaps?

Caveat: I'm not a mechanic but that would be my WAG.

 

It doesn’t sound stupid. It just sounds like brutal leg day.

 

....mine does the same.

 

Its the stupid brake system, it seems to apply a lot more "engine assisted" pressure than most other vehicles I've driven. Then when you are stopped at the first stop the system has exhausted all it's stored / reserve power, so when the rpm increases ( I don't know why the engine does that) you need a lot more actual foot pressure to keep still than you did to actually stop. After you've driven a while the system has built up a lot more reserve pressure, so the problem doesn't arrise as much. The OR has a different brake system to the Sport, I thought this problem only existed in the OR & Pro.
Test this theory tomorrow morning by applying slightly more pressure to the brake after you come to a stop.

 

I have the same problem. The first two stops in the AM..you're slowing down then just about to come to a complete stop and we "lunge" forward. Pretty annoying, but hey what do you want for 35k? I'll just add that to the list of BS that seem to come with this truck. I have the OR by the way.

 

Found this FWIW:

https://www.yourmechanic.com/question/car-jerking-forward-when-stopped-by-jessica

 

I have noticed there is a surge when turning the steering wheel at a slow speed. I have to be very careful pulling in and out of the garage because of the jumping. When you are coming to a stop are you moving the steering wheel at all?

 

I just picked up my 2017 trd sport a week go it started with the surging in and out of a tight parking spot ????? Also I have the clunk as well after coming to a complete stop ? Disappointed....

 

Should I take it back? lol problems with a new truck not good taking it into dealer Wednesday

 

Defrost kicking the AC compressor on/off causing surge in RPM's?

 

Is your cabin air set to defrost? The AC compressor will cycle on and off to assist in drying the air. When this happens there is an additional load on the engine and the computer bumps up the idle to compensate, putting more torque through the converter to the wheels. You have to press the brake harder to overcome this.

 

Must be "characteristic of the vehicle".

 

Maybe the TSB reset will help

 

I thought it was just me, my truck exhibits all these exact issues, the lunging is exasperated by turning the wheel... So now that we’ve figured this out, how do we counteract it? Trying to prove to your insurance that it wasn’t your incompetence as a driver the factor for the accident is gonna be pretty hard to do.... Top off fluids? Call the preist? Go to dealer? Provide offerings? Maybe if we think of something we can prevent fender benders/damaged bumpers/injured pedestrians (yes she has lunged forward at someone as they were crossing in front of me)

 

I’ve done everything suggested and my truck still does this lunging thing and after a year I’ve just learned to live with it as a manageable characteristic of the vehicle - I just know to stay alert those first few minutes when coming to stops, etc., mine also tends to do this when pulling into my garage so I’m always being super careful it doesn’t lunge into my hot water heater!

 

Same with my SR5. Always seems to happen when backing in my carport when my mirror is close to the wall. Makes me curse some days.

 

There is also a richer mixture and higher idle due to it just being cold. The trans fluid is also cold and does not flow as easily as when it's warm so it turns higher idle to motion. The steering booster also causes extra load on the engine via the alternator or hydraulic pump so yanking the wheel while the truck isn't moving causes sudden RPM swings the ECU tries to compensate for. The shocks will feel stiffer until they warm up too and not be there to pick up gentle weight transfer making everything feel more abrupt. Differentials and transfer cases will have a little more stiction. The rubber compound of the tires too - if you leave it outside in 0F temps they can feel like flat spotted rocks for a few miles.

I think softly suspended tall vehicles exaggerate the feeling because any jerking translates to dive/roll you wouldn't sense as much in a lower sedan without all the suspension travel pogoing about.

You can blame Toyota if you want but, really, it's just cold.

 

My Toyota car has done the same for years since new.

 

Why it happens I don't know, I have sr5 same thing, I just put it in neutral at a light, I go in for 5000 mile service Friday, we'll see if the yo-yo's say or do anything about it. I don't expect much, but this will be my first dealings with taco service poeple. If any Pittsburgh guys know a good service place they trust and have had good experiences with please let me know.