Edmunds dealer partner, Bayway Leasing, is now offering transparent lease deals via these forums. Click here to see the latest vehicles!
Popular New Cars
Popular Used Sedans
Popular Used SUVs
Popular Used Pickup Trucks
Popular Used Hatchbacks
Popular Used Minivans
Popular Used Coupes
Popular Used Wagons
Comments
Here is more information.
http://ilot.edu.pl/KONES/2001/JOK2001 NO 1-2/R39.pdf
That's only fifteen pages, but it does a good job explaining what a misfire really is and how the PCM will see it if one occurs. (I could link some SAE white papers but you would have to pay for them). If I was presenting a class one of the leading questions would be does a crankshaft turn at a steady speed for any given RPM? The answer is no, it does not. That's why the "damper pulley"is attached to the center hub with a rubber coupling. On every compression event the crank slows down, and on every power event the crank speeds up. The PCM learns these changes in velocity as well as any variations in the crankshaft sensor profile and once that is done then it can detect if an acceleration event failed to occur. If you want to get real technical, the PCM watches the crankshaft accelerate between about 15 and 125 degrees of crank rotation after TDC on a power stroke for each cylinder. Since the PCM also knows which cylinder should be firing it can set either cylinder specific misfire codes such as a P0303 (cylinder #3) or if the misfires are counted on multiple cylinders then the P0300 might be appropriate. The system also is dependent on engine load, the greater the engine load, the more air and fuel that could enter the cylinder, therefore the hotter the catalyst might get to be if it had to clean that up. If the catalyst temperature could exceed 1500f-1800f then that would be a misfire that is scored as a catalyst damaging misfire and that results in the flashing MIL. If the misfire occurs at a low enough level (the 1000 rev counter and a light engine load) then it's more likely to only have an impact on the vehicle emissions and that misfire will generate a code but not flash the MIL. As I described earlier, you have this backwards. The carbon buildup does occur in the cylinder, but that's not the problem cold. Restricted airflow past the intake valve is a much bigger issue, especially since the injector will get all of the fuel into the cylinder since it sprays directly into it. If you get all of the fuel that the cylinder "should have" needed, but fall short of the air for that fuel, then you will be too rich and that causes incomplete combustion and a lack of push on the crankshaft, aka a misfire.
If this is all overwhelming we haven't even begun to add in cylinder to cylinder Air/Fuel ratio imbalance and false misfires caused by anything external of the engine that can make the crankshaft slow down when it should be speeding up. A bad U-Joint (seized) can cause a PCM to set a P0300.
There are various theories about why DI engines are susceptible to this but the one that seems most logical to me is that after the engine shuts down, a small amount of fuel is left sticking on the valve--when this is combined with a new engine start, you get a certain amount of oil from the PCV system and this can create the carbon issue.
One solution that you can buy and add-on is a capture device that traps oil from the PCV and "captures" it for later removal. That requires a bit more maintenance on the part of the owner of the DI engine, but seems to me a small price to pay if it solves the problem.
If it turns out NOT to be the throttle body but rather an actual carbon buildup, the only real fix is to remove the intake manifold and clean it (maybe even with a blast media). That's not a cheap fix if the owner has to pay for it. Additives are a waste of money for this problem, once the carbon has deposited.
Even if the intake is cleaned, you still have to worry about it happening again in another 40K miles or so. Some say that top tier gasoline additives and occasional shots of Seafoam will mitigate this buildup, but I don't think it can stop it without some further engineering interventions.
Turbo chargers have always run hot, its raw exhaust gasses that drive them. The turbo takes the energy that is still in the hot exhaust gasses and uses it to force more air into the engine, creating more (and hotter) exhaust gasses. With forced induction, the engineers can take a small engine and produce a lot more power when needed, and still have the advantages of the smaller sized and therefore lighter weight engine when a lot of power isn't required. The change to turbocharging as we see it today isn't about being cheaper for any individual but taken on a whole its a real game changer. The use of turbo chargers BTW also brings with it the requirement for very precise servicing. Any skimping there can easily yield even greater expenses for the vehicle owners.
So DI is being brought back to pad dealer profits with expensive engine carbon build up cleanings.
Now combine that with how far people drove each year as compared to now. Then we have the last pieces of the puzzle. They didn't use variable valve timing like we are today so exhaust gas reversion wasn't a concern. They also didn't even have PCV systems and nobody cared one bit about what was coming out of the tailpipe.
Like many of you, I'm a mom of two awesome boys. When your car loses power like that, it's dangerous to their well-being, not just mine. (I'm petrified of driving on the highway, for fear that it'll happen there, and with more serious consequences!) This is compromising their safety, and that is a BIG problem for me.
I'm also a new creative/media business owner, and this situation has me suffering the woes of having to cancel or reschedule client appointments. Now I'm losing income needed to PAY for these expenses, on top of everything else! (Two boys eat an awful lot, too...)
I just want my car fixed, a rental issued during repairs, and at no more expense to us (or my insurance company, for that matter) whether in the form of money paid for repairs or in income lost. I just want the car that I paid for less than a year ago to be worthy of that price, (yes, yes, minus depreciation, I get it) as well as the safety rating that supported its selection.
So fill me in? (11 pages is A LOT to read, bear with me.) I see these GM "social media" folks requesting info from various contributors to this thread. Do they actually get anything accomplished? Is there a way to get this handled quickly? (Or has anyone "mysteriously disappeared" after responding?)
Beyond that, there is more than "ample fuel" for a class-action lawsuit available (or at the very least, an epic yet highly entertaining social media nightmare). Would that fulfill GM's prerequisites for a recall?
Any input, suggestions, or further fuel for this fire is greatly appreciated & highly regarded - thanks in advance!
Given that tracking down the cause of the reduced power can be tricky, it requires patience all around...from the owner, from the technician, and from the dealership with the whip who wants his technicians to hurry up.
Is it fixable? Absolutely. Is it likely to be fixed the first time? Apparently not from what we're reading here. Of course, we don't read about the successful first attempts, as those are rarely posted.
Short Answer: There is no one reason why this happens.
There are techs that make easy work of the problems described in this forum and many of the others, only to be treated in such a manner as is demonstrated by comments like "They don't hire techs with IQ's above room temperature". When it really comes right down to it, you shouldn't wonder why it's hard to find good techs that can handle this work easily. You really should be wondering why there are any at all.
I don't know how the costs were spread out between shop and customer, but the next day, the car ran great and has continued to.
The safety is such a concern for me and my family. We travel some of the worst winter roads in PA that also have heavy tri-axle truck traffic. We have no family in the area to assist with shuffling the kids around and really
I just want my car fixed, a rental issued during repairs, and at no more expense to us. I just want the car that I have only made 5 payments on to be worthy of that price as well as the safety rating that supported its selection.
Is there a way to get this handled quickly?
Thanks
Thanks!
Also, just had the Stabilitrak alarm for the 3rd time on 2-15-16. Only 800 miles since last alarm.
Lets try and break down exactly what was written. Based on this description, the first step is to check for codes in all of the vehicle's modules, with no assumptions. The ABS light on, suggests two possibilities. Either a failure has occurred with the ABS system, which would of course cause the Stabilitrak and Traction control systems to be disabled, OR there is a communication issue not permitting the instrument cluster to see information from the ABS module. Even that means very little until some actual information gathering (the discovery phase) has taken place. Without driving the car and experiencing the symptom myself, this part if the description doesn't help at all. It's a mistake to attempt to guess what this means and do anything with it. Even if this was worded more clearly the tech still has to replicate the concern. The tech is going to have to rely on the seat of the pants feel that takes decades to acquire in order to start narrowing the focus to the system that is encountering an issue. This is something that cannot be taught in a classroom and is easily lost by people who stopped being techs for what-ever reason (if they ever learned it to begin with). That's one of the biggest problems with non-technicians running the shops. Today the odds of finding anyone in management that can do this is about as likely as one of them figuring out that Jeep I posted on the other thread. That's why they don't pay the techs correctly for diagnostics, they really don't know what it takes even though they work in the same building. The pay plans they run pay the techs better to flush brake fluid than they do to figure out what's wrong with a car that is genuinely broken.
The GM service department on the multiple times that they have looked at and kept the car (several days at a time) has not been able to duplicate the problem. They have the code reads but no device to blame. GM should take the time and isolate once and for all the problems plaguing their product line, understand intermittents are not easy to track, but with a determined persistence approach an organization with the resources of GM can come up with a solution if they wanted too.
I understand the complex nature of diagnosing such problems, as a customer I have a right to a safe and maintainable product that does what its designed for.
I ask GM to correct the defect with this products controls.
Can you describe what the symptoms were other than just what lights came on each time if there were any? Intermittent issues are pretty tough to solve. On top of that, imagine you dealing with an intermittent failure with one of your "plc" systems and not getting paid for the majority of the time that you have to invest while you are working through it.
LAN is Local Area Network, and any "U" codes setting are in fact communication codes that modules will generate against other modules if they don't receive the data that they have requested. Most transmission codes, some of the engine controller codes, and just about any codes from the antilock brake system when generated will result in the stabilitrack system shutting down. Stabilitrak as a component doesn't really exist, think of it as software running simultaneously in a handful of systems that all have to be working correctly as well as together in order to create the functions referred to that assist the driver with traction and stability control. Probably not, but that cannot be ruled out at this time. If you could get a PICO scope capture of pins 6 and 14 from the ALDL during a failure event you could see if the scope can read the data or not.. The data network utilized is a twisted pair CAN bus. (Controller Area Network). CAN uses two 120 ohm termination resistors for a total bus resistance of 60 ohm. Breaking down the entire architecture of the network you will find a module responsible for the 5v power supply, and the first bias resistor. Then you have the termination resistors in parallel, (with the second one residing in a different module) and then the second bias resistor which connects the network to ground. So the communication network runs at 2.5 volts and the respective signals go up and down approximately 1v from the bus bias for communication. This design is very resilient and resistant to external noise. The data bus does not require shielding because of the design. (Which is mandated by SAE). Ground loops are also not a concern, this article explains why. https://en.wikipedia.org/wiki/Ground_loop_(electricity)
As far as a failed sensor or controller, that cannot be determined without testing while the problem is occurring. So the problem cannot be duplicated reliably. It doesn't get any tougher than that. But at the same time, should a tech be lucky and have the problem occur and stay long enough, most top techs would locate the failure easily. The nature of machines doesn't make this plausible. There isn't a finite number of possible failures that can occur, and even if there was scores of failures could result in identical symptoms and codes. The only routine that is going to work is that the technician gets to prove what is going on while the symptom is occurring.
I just received a call from the dealership and was told that it is the steering sensor and that part is on "Extreme Back Order". Must be a popular item. The person then said that they would try to get the part from GM but it may take a few days.
The questions raised by this experience are: If the Operators Manual included with the vehicle instructs you on how to reset the failure, why is it that the Service Dept. personnel tell me that they have never heard of this happening? And if this alleged failure does not happen, why is the suspect replacement part so difficult to obtain?