Problems with unintended acceleration and buffeting

[Leverus]

I thought I added my two cents on the throttle issue here long ago but I guess I didn't. Way back when I first got the car and was figuring out how to drive a manual I was parked in neutral and playing with the gas, trying to get a feel of it for taking off. I was bouncing the RPM to about 1500 when one time it seemed to freeze there for a second and then shoot up to about 2K before falling.

Another time I almost stalled and pushed the clutch in to save it. My feet were slower then and I wasn't on the gas yet, but the engine went back to idle, sputtered a bit, then shot up to 3k and stayed there for a second or two before dropping back to idle.

Those were the only times it acted strange for me and I hope it says that way. The computer definitely tries to do it's own thing at times and you can count me in the club for not being a big fan of drive by wire.

 

[gdideric]

Unintended acceleration has been happening for decades, long before fly by anything.

For example:
Other problems may be implicated in the case of older vehicles equipped with carburetors. Weak, disconnected, or mis-connected throttle return springs, worn shot-pump barrels, chafed cable housings, and cables which jump their tracks in the throttle-body crank can all cause similar acceleration problems.

Sudden unintended acceleration - Wikipedia, the free encyclopedia

I wouldn't be so quick to denigrate new-fangled technology.

 

[Leverus]

That's true, but I'd still rather it be something mechanical that can be fixed or worked on rather than some obscure software glitch leaving it up to the manufacturer to acknowledge let alone update.

 

[Aldakoopa]

That's true, but I'd still rather it be something mechanical that can be fixed or worked on rather than some obscure software glitch leaving it up to the manufacturer to acknowledge let alone update.

Exactly. I had an old Jeep that one of the throttle linkages on the carburetor was loose... didn't cause any acceleration issues, but it would somehow cause it not to start. It didn't take much to pop the hood and move that linkage over a tiny bit and it would crank right up. If I can get my hands on something mechanical, it can be moved, fixed, replaced, or even jury rigged if need be to get by for a while. It's not like I can pull over and pop open a computer and reprogram it if I get into trouble.

 

[sx sonic]

Gdideric that is a good point, however even the statement about the causes for throttle sticking or unintened acceleration shows that most of the issues with throttle cables are the result of worn out, unmaintained, or deterioated components.

I have not look at statistics but I would bet that there have been way more incidents on new cars with fly by wire (FBW) aka electronic throttle control (ETC) than there has with cable actuated throttles .

Do I think FBW is bad? No but I prefer a cable mainly because I can control engine load/power/airflow how I see fit instead of the computer interpreting it in a manner that is not as adaptive as my foot. It has many merits and works good the vast majority of the time but when it doesn't work right it can be scarey. On a side not just the basic operating tables for FBW are massive to account for the ungodly amount of different circumstancces for driving, it is not impossibel for a situation to arise that is outside the scope of what the ecm was originally programed to see and it will substitute a control plan as best as it can determine which may be right or may be wrong.


To the people that have had this problem is there a certain temperature it occurs? Is the car warmed up? Cold, only been running 5mins? Was the A/C on? Sunny or rainy? Basically what was it like outside, and what were you doing when it happened.

Maybe just maybe there's a trend when this is happening which would make diagnosing and correcting the problem much easier.

-tyler

 

[SuperFudd]

The above scenarios seem to be based on the theory that the FBW parts are manufactured and assembled to spec. As we know all to well there are always errors in the building of an automobile. There are so many parts and processes in the making of a car that I doubt any one car is built entirely to it's design specifications, even if the design is right.
What if the throttle system is defective? What if a connector is poorly crimped to it's wire? What if a feed thru "barrel" in a circuit board is cracked? What if there is a cold solder joint? What if there is an out of tolerance resistor? What if...?
What will a poorly shielded computer do when the guy in the car next to it keys up his 1000 watt CB?
I prefer fly by cable.

 

[Chevrolet Customer Care]

I purchased my Chevy Sonic in April. I am the original owner. I have 3,002 miles on the car. This past Saturday while parking at my local Walgreens, I had my foot on the brake ready to put the car in park, when the car made a loud noise like a squeling sound, the rpms went up and then my car went forwad up the curb and into/between two yellow safety posts mounted in fromt of the PROPANE TANK CAGES at Walgreens. I am not physically hurt. I am however terrified to even drive right now. I had the vehicle towed to the Chevy dealership that I bought it at. Now I am waiting for GM to call me back on how Chevy plans on dealing with this problem. This issue needs to be addressed by Chevy with this car's accelerator problems. I have been reading the different stories on this forum. I am really scared.

Your concern is very justifiable. Please keep us posted on the status of you case. DM if necessary with the VIN#, situation, contact information, and case# if you have one. I hope this is addressed quickly for you.

Matt,

GM Customer Assistance

 

[hmae37]

Sounds like some issues amongst many others I am starting to have. My sonic jerked forward with my foot on the break. Bumper to bumper traffic, I barely lifted pressure off the brake, not completely, to inch forward and my car abruptly jerked forward, like I had turned off the a/c while driving, which wasn't even on. It freaked my daughter out, luckily it was a abrupt jerk and not a lunge forward. About 2 mins after that while no acceleration but foot off the petal completely slowly moving forward about 50 ft, my car jumped forward and in about 3 ft managed to slam on the brakes and just miss hitting the suv in front of me. about 30 secs after my idle dropped so low my car almost stalled, i was watching the rpm gauge and no movement in the gauge what so ever. I have had multiple similar issues involving what seems to be the idling or the transmission gear or settings itself. No codes, No check engine lights. Oh and that was all without air on, with air on its worse, with a/c on its 3 times worse. No fix and more than a handful of dealership visits. My daughter effective tonight with the new noise it is making, refuses to ride in my car. She is 12, and she told me she doesn't feel comfortable with her brother in the car either. What choice do I have? As of now....none. I HAVE to work, which means I have to get them to the sitter and school too. I have no other car. I LOVE my Sonic but desperately want it fixed. I want, firstly, my kids to feel safe in the car and then I want to feel safe in it. I have missed alot of work due to these issues. I truly can not afford for this car to cause a wreck (praying it won't be fatal or any serious injuries) and cant afford to be stuck on the side of the road somewhere. I feel your pain, I wish to God I had a fix , at least an acknowledge one by the dealer. I wish old type mechanics were practiced, ya know, the days when you tell a mechanic the issue(s), they think about it and check the possibilities. Compared to now it's, take it around the block, turn off the radio and listen, nothing in that 2 min circle around the block?...... well there's nothing wrong with it. sorry bout your luck. GM has been great though, not so much for the dealerS. I pray mine does not get this bad. I wonder if GM would pay for cab rides to at least transport my kids?!? Not a chance I'm sure LOL

 

[Lovehanayo]

I wonder if GM would pay for cab rides to at least transport my kids?!? Not a chance I'm sure LOL

Anytime you take your car to the dealership and they have to keep it overnight, they give you a free rental to use in the meantime. I've never had a dealership deny me a rental to use in the meantime to get to work/school/etc.

If current dealer is giving you issues, try and go to another one, they might be more helpful.

Vandergriff Chevrolet is shady as hell and they don't really help with problems, only make them worse which is why I go to moritz Chevrolet or Bruce lowrie. Sometimes making a report to the BBB can do wonders too or calling a head dept.

 

[ChrisJ]

I've owned both a 1.8 auto and now a 1.4 turbo manual Sonic and never saw either do anything I considered strange.

All remotely modern vehicles (mid 1980s and up?) will not allow the engine speed to drop rapidly as it causes a huge increase in emissions. Carburetated vehicles had a selenoid, sometimes a stepper motor which would not allow the throttle to snap shut especially while the car was traveling. On TBI engines the IAC valve would simply stay wide open allowing plenty of air in. I had many carberated vehicles whos computer would adjust idle speeds via a stepper motor and beleive me if it went too far it couldve made the car do 20MPH without your foot on the throttle.

Throttle cables have plenty of issues between binding whether its due to frayed cable or dry lube or more common were streched cables which didn't allow your throttle to open completely when floored. Hard linkages like they used up until the 1980s had their own group of problems.


Now, I'm not saying anyone here is lieing and not experiencing the problems they said they are. I'm simply chiming in and saying I have not personally had them on both Sonics I owned. I drove the 1.8 auto sonic for 11K miles and now the new one just hit 1300.

 

[Dags]

While I mostly drive manuals, I've driven a few automatics over the past several decades, and every single one would roll forward slowly if I didn't have my foot on the brakes. Roll around the parking lot with a foot on the brakes, slowing or stopping when needed. No reason I wouldn't have been able to make a U Turn. I've always assumed that was "working as intended."

The other problems you report, such as lurching, I dunno about... but if you want a vehicle to stay put without your foot on the brake, I think you need to come back to the Manuals.

All cars I've driven (autos) have idle speeds. They vary from car to car. My mom's Blazer crawls without some pedal action, but I've driven other cars that had uncomfortably high idles. I did my road test in a driving school Toyota that idled at about 13 MPH, after an overly peppy start I idled through most of the course. Usually a car will settle into idle in a few seconds, but if you immediately get it in gear after turning it on, the RPMs might not have adjusted to idling speed yet. An unusual or high idle can also be a sign of several wear and tear issues.

 

[Cyric]

I wanted to provide an update to anyone who is still following this thread. It can be found here http://www.sonicownersforum.com/forum/chevy-sonic-owners-forum/14497-most-hellatious-ownership-experience-my-life-how-chevy-broke-my-heart.html#post256077

 

[attrapereves]

All cars I've driven (autos) have idle speeds. They vary from car to car. My mom's Blazer crawls without some pedal action, but I've driven other cars that had uncomfortably high idles. I did my road test in a driving school Toyota that idled at about 13 MPH, after an overly peppy start I idled through most of the course. Usually a car will settle into idle in a few seconds, but if you immediately get it in gear after turning it on, the RPMs might not have adjusted to idling speed yet. An unusual or high idle can also be a sign of several wear and tear issues.

That's what I hate about automatics. In my auto Sonic, you can feel the car trying to push itself forward when completely stopped. Luckily the car automatically shifts into neutral when completely stopped for a longer period of time.

 

[Sailurman]

Uncontrolled acceleration

First off I want to state I'm very disappointed in the immediate closing of my thread as this one is two(2) years old, refers to an unturned 1.8 model owned by a whining asshat. Admin seems a bit TOO controlling here, but hey.... power is nice huh? There, that's off my chest.

So let's try again. I'll start over here:

-------------------------------------------------------------------------------

Was driving into the parking lot at work today when my lil buddy just starting taking off on me. Cranked up to about 6K RPMs. I braked and popped it into Neutral and then shut him down immediately. Never had that happen in any vehicle and it definitely was a shocker. No probs when I started him back up.

No interference from my stock rugs. No prior issues. Not a Prius owner wannabe and I am currently tuned. I was not horrified and the car was NOT changing gears by itself. It did however appear that the rev limiter was also bypassed because I shot past 6K when I shifted to Neutral when it will typically max at about 4K in neutral.

I will detune this weekend and take it in next week. Looking for further valuable input as opposed to what has been in this thread up to this point.

 

[rsSteve]

My Sonic LTZ now has 14,000 miles on it, with the 6-speed trans. Back in July I was approaching a stop sign, doing maybe 30 in 3rd gear. As I approached I simultaneously stepped on the clutch, the brake, and put it into neutral, then released the clutch. I should add that the radio was on, so I didn't hear the sound of the engine. What I did notice was an odd buzzing in the car as the brake was applied. I kept constant pressure on the brake as I came to a stop and noticed just before coming to a stop the tachometer read 3,000 rpm and was dropping, as if I'd blipped the throttle. The brake pedal in my car is high enough that in order to hit the brake and the gas I'd have to bend sharply at the ankle to let my foot pivot enough to hit the gas. I also kept a steady pressure on the brake, so that if I was hitting the gas the rpm's should have stayed up. This only happened once and I haven't been able to replicate it, even when trying to hit the brake and gas at the same time. Since it's a manual I can always get the clutch in so I'm not particularly worried about it but it is disconcerting to think that there could be a bug in the programming where some odd action on an alternate Tuesday on my part could cause a problem...

This actually happened to me once before a few weeks ago but i didn't pay much attention. Then today on my way to work it happened 2x. I was cruising at 65 mph for about 30 min when there was construction up ahead. I slowed down put car in neutral and the engine dropped to idle like normal than as soon as it hit idle rpm's the engine began to slowly rev back up to 3k and stayed there for a few sec until I blipped the throttle. I then got back up to speed but had to slow down again. It happened again. Once it dropped to idle rpm speed it climbed back up and held steady at 3k until i gave it a little gas. Never happened again for the last 15 min of my commute.

A/c and defrost was off, floor mates secure, foot was off accelerator, temp was around 80F, very humid this morning though, and 6M/T. I am not too considered at this point since i have a manual but if it continues to happen more frequently I may consider taking it in. Just thought i would share my expereince.