Sometimes driving at 45-50 mph cruising the car will randomly accelerate for a second or two and then drop back to the speed i was at and other times it will accelerate 5-7 mph and then drop back to the cruising speed. I took it in to the dealer and they think my dad and i are crazy because they can't get the car to do it so they did some computer updates. i took the car out after and it still will do it. has anyone else had this problem?

 

TPS sensor

 

what exactly does the tps sensor do?

 

it tells the computer how far your foot is in the floor....lol

 

why would it only do it at a certain mph?

 

I didn't know we had a TPS. We have a drive-by wire setup for the throttle. I thought a TPS was for cable systems??

 

if they work the way i think they do...it could be a bad spot inside the tps where two metal parts meet....im thinkin it works like a potentiometer.....or a knob...and a metal piece makes contact with a certain length of another type of metal which varies with the position of the knob..thus creating a variable resistance...if one spot was dirty the computer could be getting false signals

 

Maybe that's the only time he uses cruise . For me, cruise > 80 mph.

I'm not sure about the linkages on the throttle cable on this one, but it's also possible that could be slipping a bit, or the ecu could think it is.

Is your car an auto? Could also be that revs are getting to low and your car is trying to comp for it? Idk - just throwing darts at the board here.

 

no its a 5 speed.

 

There is no cable for us. It is 3 sensors that work within each other to determine the throttle postion. (driveby wire)

 

IMO, I would suspect the switch on your throttle. If your car is not setting codes then the ECM thinks you are moving the throttle -- if it was anything else then your ECM would sense out-of-ordinary parameters like over-revving with TPS set, increased intake air with TPS set, and so on....just my .02s worth.

 

Its not a fault of the tps, Mine does it too...I have noticed it twice now and it did it both times at the exact same spot. I have only put 800kms on mine so i havnt had time to look into it....both times I was not on the throttle, had just depressed the brake to go down a slight hill into my shop and the car just picked up speed all by its self at about 12-13kms per hour....didnt go to fast mabe 18kms per hour but it was pulling on its own. A tps wont give you an excelerating issue, but will give you a flat spot.

 

Humor me and try this:

Find a hill. The steeper the better.

Go to the bottom of said hill.

Get the car moving up the hill just a bit until you can shift into 2nd gear.

Once you're in 2nd gear, don't touch anything, only steer the car.

You should notice it WILL NOT STALL as it makes its way up the hill, intermittently applying throttle all the way up the hill. The only way to stall the car out is to hit the brakes. I discovered this while showing my g/f what NOT to do. To my surprise the car didn't stall and I laughed my ass off as the car crept all the way to the top of the hill.

I don't know what to call this feature, but it seems normal for our cars.

The way it seems to work is if you reach 1.0--1.5k rpm in X gear, the car will apply throttle for you. I haven't fully made sense of it but I've gotten it down to where I know when its going to do it.

SO, based on the above, my guess is you cruise at 40-45 in 5th, which would be about 1.5rpms? That is right around the rpm range the car applies throttle on its own in 2nd gear.

 

There are a couple complaints with NHTSA for the issue described http://www-odi.nhtsa.dot.gov/cars/pr...aintsearch.cfm
Put in the NHTSA ODI Numbers: 10146741,10151469,10174444
It may not help you find the issue, but at least you can show the dealer you're not crazy.

 

there aren't any hills in the area i live in. i would have to drive about an hour west of my house just to get to an area with hills. the times that this happens is when i am on a level pavement.

 

Well actually you dont need a hill. It just helps to illustrate it better. You could make it happen by getting up to about 20mph on any road then simply letting off the throttle completely in 2nd gear. The car will not stall until you force it to with the brakes. I'm almost certain this is an intentional feature of the car.

edit: just tried the link bredick posted. If that is the case, then we are discussing two different things. The one I'm talking about does not involve the use of cruise control.

 

there is one in there where i have the same issue as someone else. i have noticed that sometimes my cruise control will not engage at first and it takes several hard presses for it to engage. thanks for this maybe the dealer wont think i'm crazy, but they still won't know what to do.

 

Cruise engagement issues are usually the sensor for the clutch pedal (or brake, but that seems less common on our cars), could be related, if it thinks the clutch is being pressed it may throttle down, then when it thinks the clutch is not it would throttle back up to try to maintain the 1-1.5k idle speed?

By the way, where in Harrison are you from? I'm out there alot for work at the township offices.

 

no i am not using the cruise control when its happens i just have the car traveling at a set speed with my foot on the pedal.

 

I'm wondering if it may still be related because of the way the idle speed changes depending on if the clutch is depressed or not, I would have the clutch sensor checked as the cruise issue (they should look at it if you complain about the cruise) and see if the other issue goes away with it, worth a shot, right?

What I've noticed is anytime the car is moving with the clutch engaged it will idle at around 1500, but if you press the clutch it will drop to about 1000, you can try it with the car moving in neutral, you should see it, unless mine is the weird one It's not necessarily related to the cruise, but they may both be symptoms of the same problem is what I'm saying.

 

im in behind metro beach. i live off of south river rd.

 

Now you got me thinking if I've seen any yellow SSs when I've been out there, I thinnk I did once by Metro Parkway and Crocker, headed East, don't remember when that was though. But if ever you see a blue SS/SC around there it could be me

 

you know come to think of it i think i might have seen you today bredick. you were going north on Schoenherr rd. when i was stopped at the light on hall road it was maybe 1 or 2. it was a blue ss/sc that was kinda dirty.

yeah im normally headed east on metro parkway around 3 on weekdays. i got a yellow 2.4L ss cause i know theres a yellow ss/sc around in the area too.

 

That one wasn't me, mine is really dirty, but I didn't go anywhere in my car today, but that is only a mile from my house. I know there's a blue RedLine somewhere around me too, I ran into him a couple times on Hall road. I'm thinking the Yellow one I saw by you had the low profile wing, but it was like 3 weeks ago.