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Discussion Starter #1 (Edited)
What I thought was a brake issue, its Auto-Transmission!....Experts Needed!

Okay so I'm going to be honest, I'm a young female that doesn't know anything about cars so I'll start with that...

My car, 2006 Base Solstice, automatic

Okay so I have tried to explain this to the car mechanic, my boss at work and to my father but I think I've stumped them on this problem with my sol.

Just two days ago I was driving my car on the freeway going to work like I normally do and I get off the freeway and come to a complete stop, except it wasn't the smooth gliding gentle stop I'm used to. As I applied the brake very gently like I normally do, instead of a gradual braking, it just went into a very hard brake and jolted me forward suddenly. As I crept closer to the traffic light and applied the brake again, it wouldn't give me a gentle smooth stop but many abrupt stops as if I was slamming on the brakes. Then when I accelerate again, I feel a very soft knock kick in as I accelerate

As you can imagine this situation freaked me out and I automatically took it to our car mechanic who didn't know what to tell me. He told me my brakes look fine and visually he couldn't see any problems.

My father thought of another possibility and he stated it could have something to do with the ABS kicking in when it's not supposed to.

I don't know if any other Solstice owners have had this issue before or have any idea what this problem could be.

Hopefully someone on here can shed some new light. My dad wants to spray some stuff on my brake pads but I don't want him spraying anything on them till I check on here if anyone else has had similar issues.
 

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Have your brakes ever been replaced?
I am surprise the mechanic did not do any testing.
It could as your father suggested the ABS is having a problem.
 

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At 61K miles, I would hope the pads have been replaced. Also, the brake fluid should have been flushed twice, and is due for the third flush, now. Not having either done can cause improper brake response, especially water accumulation in the brake fluid. Usually, that kind of thing results in rapid brake fade, but I don't know how ABS would react to it, and don't intend to find out, first-hand.
 

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I'm thinking it's ABS related. I know that changing moisture levels in brake pads can cause them to be "grabby" or loose, but the fact that you were well into your drive leads me to think it's electronic. Obviously could be wrong. Let us know what you find out though!
 

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I'll throw in on the other side of the fence. ABS is designed to pulse the brakes by means of releasing the brakes rapidly. I suspect that if you had an ABS issue and it was "kicking in" you'd have less grabbing instead of more. Also, if you had ABS issues, chances are that it would throw a code. Are your pads due for replacement? It might well be some kind of contaminant on the rotors/pads. Have you had any more issues with it? Did the mechanic actually pull the wheels off to inspect the calipers?
 

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Discussion Starter #7
I'm thinking a light would have came on telling me there was an issue regarding ABS but again I'm not exactly sure.

When I approached him I told him at that time it had only happened once, which was the truth at that time. However, since then(fri morning) it's happened once a day usually after I've been driving the car for at least 20 minutes(I have a 35 min commute to work and 50 min commute back home) everyday. I will slow down getting off the freeway and between 25-30 mph as I apply the brake for a red light, it brakes hard suddenly and causes a tire screech. As a result I'm afraid to apply the brake because I certainly wouldn't want that happening if I was going 65mph. It seems to only do it when I'm going at low speed on the streets or during stop and go traffic on the freeways.

Here's the thing, I tried to get my dad in the car when it started occurring again and OF COURSE when he's in the car, it doesn't want to do it. It's very inconsistent and it's hard to get a witness except for those few strangers that share the road with me when it happens off the freeway on Imperial Hwy.

I could try and get a quick video on it and post it on youtube for you guys to see it.

A possible solution could be replacing the brake pads, doing a brake flush and seeing if that works. Otherwise isn't it the mechanic's job to figure out what the issue is? My dad wants to spray some brake stuff on the metal, an "old school" method he used with his older vehicles however I'm not sure if it works with cars like these. It's all electronic and it could very well be an electronic issue that needs to be fixed.

I'll keep you guys updated on this issue, like I said I tried looking up this issue on here and I haven't found anybody else that has had this issue. Let's hope for the best and worse comes to worse, I guess I can drive that big ugly silverado till the sol is fixed... I don't really trust it on the road to be honest.
 

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I think it may be transmission related, extremely hard downshifts. This can be caused by communication problems between modules and usually leaves DTCs, sometimes in the history file. Have that checked out and get the codes deleted.
 

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From both of your messages here, I am left with the impression that it is your automatic transmission that is causing the issue. There is constant communication between your engine computer (ECM) and the automatic transmission computer (TCM). When the TCM sees unexpected values being reported by the ECM, it will sometimes shift into a "safe" mode, which exhibits itself by downshifting very abruptly. In your case, it just happens when you have your foot gently on the brake pedal.

The problem isn't your brakes, it's the transmission.

.
 

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I think Dave is onto something. I overlooked the fact that it was an automatic. From what little I've learned about it, the automatic does have features on it to force downshifts (like going downhill for example.) Search the forum and I'll be you'll find a similar issue posted.
 

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I'll let the others pursue the transmission possibility (and it may well be that). I'll stick with the brakes. Please under stand that I do not want you to do anything dangerous, but when it does this, does the car tend to pull to one side? If so, in which direction? the next time it does this and IF it is PERFECTLY SAFE to do so, and at LOW SPEED, can you only lightly place your hands on the steering wheel to give it a chance to pull to one side (be VERY careful doing this on the street. Obviously an empty parking lot would be the ideal location to attempt this). You only need to verify that it is or is not pulling to one side when applying the brakes (remember, only do this when there are no other cars, etc. that you might hit should your car pull in one direction) which you may only need a micro-second to do so. You might even want to try this the next time you apply the brakes (even though the issue doesn't seem to be manifesting itself otherwise). I don't think your dad can hurt anything (except his health by breathing the fumes) by squirting the calipers with brake cleaner, but if you have a leaking or loose caliper, the brake cleaner will only help temporarily or not at all. Actually, brake cleaner is highly flammable (don't ask), so be sure NOT to spray it onto hot brake calipers/rotors. Let us know if the car pulls to one side while applying the brakes.
 

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Next time when you are driving and want to stop.....kick the Xmission into Neutral....you will then know that the problem is not the brakes.

Take care :thumbs:
 

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Next time when you are driving and want to stop.....kick the Xmission into Neutral....you will then know that the problem is not the brakes.

Take care :thumbs:
Leave it to my friend SolNut to come up with a very practical diagnostic solution to either confirm or dismiss the auto transmission as the source of the problem.

.
 

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That's not true, my car has 71,000 miles and still has over 50% left on the original pads.
Interesting - I'm almost half way through mine at 27K; maybe it's the autocross and driving roads like the Dragon. Hmm.

The transmission is a good suggestion; can you tell if the front wheels are grabbing, or just the rear? I should think you'd feel it in the steering if the front brakes are behaving that way.
 

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Discussion Starter #15 (Edited)
Thank you guys so much! There are a lot of empty parking lots with no cars around to test my car out and see if it's really the brakes or the automatic transmission.

Another clue is if it were the brakes, it would be more consistent every-time I applied the brakes right? But this issue only occurs after I've been driving 65-75 mph on the freeway for a period of time and then get off to take the streets, right when I start braking on the streets it starts acting up.

Interestingly when I turned off the car right when it started doing it, and turned it back on again the problem stopped.

Again I'm actually surprised my engine light doesn't go off because of this and I have to be a detective on this issue but you guys are making it easier helping me out.

I'll also look up automatic transmission issues on this forum to see if anyone else has had this problem too and I'll keep you guys updated
 

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While this may very well be a brake issue, based on the fact a mechanic took a look at can't see a problem, I'm beginning to think this is the automatic transmission acting up. I was in an auto GXP, and I was shocked at how harsh the down shifts were at times. Felt like a sudden hard brake-jerk.

Like others have mentioned, if you shift into neutral and it's gone, or when it does happen, you see the engine rpms jump up when it jerks, it's the transmission downshifting clumsily that you're feeling.
 

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I am also going to go with ruling the transmission out first, before the brakes. The brakes are pretty mechanical in nature, even with ABS, and if there is a problem there mechanically, the mechanic should have been able to see anything that was grossly wrong. The other reason I would look at the transmission is that we see issues like this on other automatic cars, a heavy down shift at slow speeds, only when decelerating and at about the speed you are talking about. If I had the car here, the first thing I would do, is remover your air flow meter from the car (held in by 2 bolts and a single electrical connector) and see if there is a build up of any dirt on the meter. Clean the meter (with MAF cleaner found at most auto parts stores) and re-install it in the car and drive it. On the automatic cars, if any dirt gets on the air flow meter, there is a mis-match that happens with the ECM and the TCM in the car on calculated torque and so the TCM goes into a safety mode and increases the line pressures on the transmission, which results in a very abrupt shift, usually noticed on deceleration first.

Hope that helps,
Dave
 

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If it is the transmission, there is more than anyone ever wanted to know here

http://www.solsticeforum.com/forum/f12/auto-transmission-suckage-65252/

Basically, there are several ways that your transmission controller can go into protection mode. Protection mode results in the hard shifts when decelerating.

A way to check is to reboot the car to clear all codes and history. I do this by pulling the positive battery terminal for 30 seconds or longer. Then drive the car and see if the hard downshift behavior is gone. If it is, then you need to diagnose why it entered this mode.

Protection mode results when the ECM data to the TCM do not agree. This can happen with

A dirty MAF sensor, see Daves comment above. You can use MAF sensor cleaner from a parts store to clean the MAF

A cam position sensor is failing or has failed

A cam position servo is sticking, failing or has failed.

If you reboot the car and the problem is gone for a few days but then returns, you probably have one of the above issues.

Good luck.:thumbs:
 

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Discussion Starter #20
Did I mention that my engine light went off a few weeks back basically with the code that stated P0171 - System too lean(Bank One). The mechanic told me it mean't too much Oxygen and told me my K&N Air Filter was totally dirty and needed to be either cleaned or replaced.

Over the weekend my dad cleaned and replaced the air filter and confirmed that it was incredibly dirty. I didn't think it was related to this issue until I started looking up automatic transmission problems on this forum and found out there is a relation between perhaps the dirty air filter and the automatic transmission problems I've been having.

By the way, as odd as this sounds my car behaved without the issue today. I know the problem didn't magically go away and I'm sure it's still there. I'm becoming more relieved that I have found others with this similar issue. This is also the first car I ever owned so I'm learning more and more about how the car runs as these errors start showing up. I really don't like the car issues but I use the car as a daily driver and I can't expect it to run perfectly forever.

It seems that all signs are pointing to a possible dirty MAF sensor that needs to be cleaned.
 
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