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Sorry if you read this in a "general forum", but I am Desperate to find a solution for this: When starting from a standing position, the accelerator is depressed, then the nose of the car "dips-down" almost to a "Stall" then without notice, it LURCHES forward, throwing my head back like a Drag-Racer, and spinning the tires. Some day this will happen when I have an 18 wheeler coming at me, and I HOPE it doesn't hesitate TOO long !
Anyone else ever had this happen? My dealer had the car for an entire day, and (of course) could NOT duplicate the situation. It is a 3 month old Sorento, with the 4-cyl. GDI engine.
Well since it's under warranty, I wouldn't bother working on it, but...
It could be the throttle position sensor. Why? Because this tells the computer how much torque you want (e.g. how hard you're pressing the accelerator). If it has a dead spot, and you hit it just right, the computer might freak out like yours does.
I don't know if the GDI has drive by wire, but I'm assuming it does. So it could be the motor in the throttle blade. Why? Well this is ultimately what throttles the engine. So if it sticks, then yeah, this could happen.
Last thing could be the air idle control valve. Why? The IAC controls a small amount of air that bypasses the throttle valve. It does this to allow the engine to idle smoother and not stall after you take your foot off the gas. If the computer thinks your engine is going to stall, the IAC is where it usually goes for help first. I would never have thought it was possible, but the IAC valve can allow enough air to "get by" to rev your engine to near redline. I've had this personally happen to me (Well, it free-revved to 5,000 rpm) on a SRT-4 that I have. The car would drive itself at 65+ mph in 5th gear and my foot completely off the gas. New IAC fixed the problem -- I think the old pintle was wore out.
Again though, I wouldn't touch it though, it's under warranty. If you are really worried about it, you could try to capture it yourself by buying one of those tattle-tail OBD-2 recorders they sell for you to record how your teenage kid drives. Just leave it in there all the time and after it does it again, wait a few seconds and turn off the car and unplug it. Take it to your computer and have it spit out the last start-stop cycle and take that to the dealer. They should be able to see what happens if it logs:
- IAC movement
- vehicle speed
optional ones, but might help the dealer out more:
- fuel trims (to see why she started to stall)
- ignition advance
Sounds EXACTLY like the problem my Sedona had when the intake hose dry-rotted. Obviously, on a vehicle that new, your intake hasn't dry-rotted. However, there could be unmetered air getting to the throttle, which is ultimately what was happening with my Sedona. It would intermittently lurch forward on acceleration, because the air was entering past the Mass-Airflow sensor. I would check and make sure there are absolutely no openings in the intake tubes between the MAFS and the throttle body. What you describe is EXACTLY what my Sedona did.
I'd also be curious if this has anything to do with the downhill assist feature. You said the nose of the vehicle goes down when stopped before any movement which I can only see happening if the throttle is being applied but the brakes are holding the vehicle in place... though that usually lurches the nose up so I dunno... As said, take it to the dealership tell them you don't feel safe driving hte vehicle and how to replicate it. If they don't help you then say you want your case escalated to corporate or call corporate yourself and express your safety concerns.
just throwing this out - but by chance your not putting your other foot on the brake at the same time your accelerating?
I know this has happened before, when people drive with two feet on an automatic. The system is not designed that way anymore, it used to be okay on older vehicles.
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