car accelerates by itself? [Archive] - GrandAmGT.com Forum

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slowassgtx
03-30-2005, 06:13 PM
Ok so this is my gf's 99 grand am Se and I havent had a chance to look at it yet. But here is what she said. The car will accelerate to 10 mph without her pressing the accelerator and keep doing it throughout her braking process. She can barely stop the car over the acceleration. It did it once today and has never done it before and didnt do it the next time she drove it. Any ideas
Here is what I am thinking
1 stuck throttle cable
2 torque converter
3 tranny issue

thanks for any input u may have\
nick

atc3434
03-30-2005, 08:36 PM
TPS sensor... bet its bad, causing a high idle, hence the forward speed. Probably shifts like hell too...

Syracuse huh? Awesome, I'm from Weedsport. Whats your car look like, maybe I've seen it around? If your interested, I'm trying to get a bunch of people to meet up some time, the more the merrier.

slowassgtx
03-31-2005, 11:45 AM
well its my gf's car. I have a 00 SS camaro, u might see me around its dark blue with chrome zr1 wheels. Thanks for the help on the GA though...

2003SCT
03-31-2005, 12:05 PM
I've had that happen like twice too..coming out of work after work..

CHRIS

mr_eh
03-31-2005, 12:25 PM
mine does this but i can brake it easily, but after i start it it'll start rolling on its own then surge and take off ... its rather amusing...

1hotgagt
04-02-2005, 03:56 PM
mine does it too while im coasting in traffic it just takes off but it easily stops when i step on the brakes

dcb2001gt
04-03-2005, 09:43 AM
It is definitely the TPS sensor. Don't mess around change it. It only costs ~26 bucks and changes in about ten minutes.

Graxall
04-03-2005, 10:01 AM
little off topic but do our cars have an idle control or is it just manual cars, i know my friends mitsu. 3000gt has a idle control that u can get to to adjust the idle. As the for the acceleration my car does the same thing but not barely noticable, also for fun with this go on a major highway and put it on cruise control at 80mph and put ur feet up, u slow down then the cruise kicks in and it feels like ur accelerating to 100 :-P

2002AmSE
04-03-2005, 10:53 PM
What rpm's is it running. When I start my car with a cold engine and put it in gear it and it will accelerate to about 25 mph without touching the gas. It's because my car idles at 1200rpm when the engine is cold for the first few minutes. It has done that since I got it.

If the rpm is higher than 1200rpm while in gear with no gas, theres a problem. If after 15 seconds after starting the car it hasn't dropped below about 1200rpm, there is a problem.

Some people will say my car has a problem, but I think that something changed in the years, my moms 99 will start in the dead of winter and immediadetly idle at 600rpm, but everyone I know with a newer grand am does the same as mine, but maybe someone is still wrong, if something is 'wrong' with mine I won't fix it because it isn't causing any harm.

1hotgagt
04-04-2005, 06:46 AM
how do you change the TPS sensor and were is it located?

italo_grandam
04-04-2005, 08:15 AM
my 99 grand am se was doing the same but i unplugged my cruise control box under the hood and covered the electric outlets with plastic and so far so good it used to do it a lot but now its ok. i found that if you pull over turn the car off and re-start the car it sometimes stops the problem, it can be very dangerous to drive around with since it tends to accelerate when stoping

ItsMeScottG
09-19-2013, 12:25 PM
TPS sensor... bet its bad, causing a high idle, hence the forward speed. Probably shifts like hell too...

Syracuse huh? Awesome, I'm from Weedsport. Whats your car look like, maybe I've seen it around? If your interested, I'm trying to get a bunch of people to meet up some time, the more the merrier.

I know this is a very old posting, however this is the only post that I can find that sounds similar to the issue that has been occurring with my GA. Sometimes when I start my GA and put it into drive, my car takes off by itself without me pressing the accelerator. My car did it again after work last night, without me pressing the accelerator my car was accelerating to like 25mph. I restarted my car twice and it was still having the same problem so I drove it a few miles down the road and then restarted my car again and the issue was resolved.

This issue has been happening for a few months off and on with my GA. The issue is so annoying, I can deal with it by using the brake petal but id really like to fix the issue. No dash lights are on at all what so ever, any ideas?

sleepyalero
09-19-2013, 12:48 PM
That sounds like a problem i have every once in awhile as well. Car idles high i cant put it in first, give it no gas and it goes on its own and accelerates then hard to stop. So far i havent had a problem, but idk what it is.

ItsMeScottG
09-19-2013, 02:11 PM
That sounds like a problem i have every once in awhile as well. Car idles high i cant put it in first, give it no gas and it goes on its own and accelerates then hard to stop. So far i havent had a problem, but idk what it is.

Same issue here! anyone have any ideas as far as a fix for the issue?

sleepyalero
09-19-2013, 02:32 PM
Well since i have a 6 speed im not sure. I can let the clutch out without gas and it pulls like im giving it gas. Hasnt done it for a couple weeks now.

rjs_boy
09-19-2013, 05:43 PM
Only time I've had that happen was when the PCV tube stopped sealing into the UIM, behind the Throttle body. The car idled horribly and the vac leak was significant enough that once I got it moving, I didn't need to press the accelerator at all. Going to the parts store was kinda fun, having to run it in 2nd gear to keep within the speed limit without having to ride the brakes. But fixing it in the parking lot and having it run perfect on the way home was also nice.


You don't mention rough idling or anything which sounds like a vacuum leak...have you tried disconnecting the cruise control cable from the throttle body?

How is the car idling when it acts up? Does the idle stay high, or bounce around?

I would suspect something either vac leak or throttle related is causing this...sticky accelerator cable, malfunctioning cruise control, buildup in/around the throttle plate, IAC valve.

sleepyalero
09-19-2013, 06:01 PM
Ive cleaned/replaced all sensors coming out of the TB. I could try to see if its my cruise cable sticking but i doubt it.

plastic_indian
09-19-2013, 07:35 PM
TPS or IAC problems are probably the most common causes of this on the LA1.

If available, use a scan tool to check for pending or history codes. (Or current MIL codes if the engine light bulb is burned out!)

Check the TPS for a smooth transition from near 0 volts closed to near 5 volts WOT. In the absence of a scan tool an analog multimeter can show this more clearly than a digital. TPS problems usually set trouble codes, however. The pigtail to the sensor can also become damaged, resulting in a quirky signal.

IAC problems are harder to look at without a scan tool. Ideally, you want to monitor desired idle RPM, actual RPM and IAC counts for disparity. A sticking IAC will, in many instances, not set a trouble code. A stuck IAC can sometimes be cleaned, but many times this is fruitless. If you do not have a scan tool, rapping on a suspect IAC with a screwdriver handle while the problem is presenting will often allow the idle speed to normalize or at least fluctuate.

ECT or IAT anomalies (particularly an open circuit, which causes a -40 F reading) can cause elevated idle problems, but this again usually sets a DTC.

I know of one particular '04 that has been plagued by this intermittent problem. While it is exceptionally well maintained, it is quite high mileage. We have not been able to resolve the issue to date. If time/money/epiphany all come together at some point and we find the cause, I will try and remember to post.

sleepyalero
09-19-2013, 10:58 PM
Ive changed all those sensors with so far little luck atm . I am getting hpt soon and will do some data logging to see if i can get the rpms to idle high, if it does i can see whats opening up and can hopefully rule out, why.

ItsMeScottG
09-24-2013, 11:06 AM
Would changing the TPS sensor help resolve the issue? Anyone other than me and sleepy experienced this? My car hasn't done it for a few days now but I'd still like to fix the issue so it doesn't happen again.

PhantomLover007
09-24-2013, 11:17 AM
I'd go w/ the TPS sensor too. Mine has done it before

ItsMeScottG
09-24-2013, 01:34 PM
I'd go w/ the TPS sensor too. Mine has done it before

Thanks, I just got the AcDelco TPS sensor from xl, ill install it this afternoon.

ItsMeScottG
10-22-2013, 05:20 PM
well I installed the new TPS sensor and it seemed like it stopped the issue but yesterday the issue started happening again. Any ideas? Id really like to get this fixed and the dealership cant seem to figure it out.

DaRkWaVe
10-23-2013, 06:50 PM
My car does this very briefly when I'm pulling my car up the driveway into the garage. As I get to the lip of the garage floor my car will surge forward. I have to be careful because I feel like I will end up going through the back of the garage if I don't keep my foot hovering over the brake.

In my opinion, it has something to do with the way the vehicle senses when it is going uphill. When it senses uphill conditions, it gives the engine a little more throttle. I could be wrong. Just trying to help.

ItsMeScottG
10-23-2013, 06:52 PM
My car does this very briefly when I'm pulling my car up the driveway into the garage. As I get to the lip of the garage floor my car will surge forward. I have to be careful because I feel like I will end up going through the back of the garage if I don't keep my foot hovering over the brake.

In my opinion, it has something to do with the way the vehicle senses when it is going uphill. When it senses uphill conditions, it gives the engine a little more throttle. I could be wrong. Just trying to help.

Mine does it completely randomly while driving.

I replaced my TPS sensor and it didn't resolve the issue. Well I also replaced my IAC sensor and cleaner out my MAF today. Hopefully these things will resolve the issue. I post my results in a few days.