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Discussion Starter · #1 ·
Hello all,

I have been fighting a problem with our 2009 Traverse. I have also been fighting a warranty service claim filed with GM to get them to perhaps actually try to diagnose the problem.

Two dealers have told me there is nothing they can do - no stored codes.

GM refuses to fix the vehicle and instead wants to give me a voucher for $4000 off a new vehicle.

So anyways, I have spent the last several days searching this forum and find a few people that either have this problem, or sounds extremely similar, but have not seen a resolution.

So the basics - 2009 Traverse LTZ. Bought used 20 months ago with 50k on it. Now has 100k on it. It has had this "bucking" problem since we bought it. It started out extremely rare and mild and has evolved to be pretty severe, completely predictable, and thoroughly annoying.

It originally only happened in 6th gear, but now does it in 4th, 5th, and 6th.

Basically - part throttle, light load, slight grade or hill. 45 to 60 mph Engine will start getting to wear it is working, starts to sound "different" and run a bit rougher, then it will buck or hesitate. It will not always buck or hesitate once it runs rougher, but it will ONLY do it after the load, sound, and running rougher have started.

Dealer has rebuilt transmission, put in new timing chains, other diagnostic work.

I have started data logging this truck with the torque app and during the "running rough and bucking periods" I see several very strange anomalies in the data.

It is worse with the cruise control on, and usually happens at fixed speed, or near cruising speed when speeding up.

Specifically:
Engine Load goes rapidly to 100% and stays there (even though speed, throttle position and grade are unchanged)
Engine load absolute goes to 109%
Throttle Position Manifold goes to 83% (which is essentially pegged) even though I have not pressed the pedal any harder
Volumetric Efficiency (Calculated) goes very high
Fuel Flow goes high, in a very non-linear relationship

In laymens terms, it seems like the fuel flow is not right (likely high) the throttle is not open, so it runs rich, rough, bucks, and is essentially trying to stall. The transmission used to almost always kick-down a gear but not anymore. It often just stays in gear - usually 6th gear.

I have my suspicions, but hoping to get some feedback from the group.

I am an engineer, been a car guy for 35 years, know almost everything there is to know about cars (except for GM die-by-wire throttles). I am good with data collection, analysis, trends, graphing. I have an AWD chassis dyno available 15 minutes from my house. I am willing to spend the cash there to make it do this and diagnose it in real time.

Any suggestions?

It is NOT the tires, engine oil level, coil packs
 

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I can offer no help - only sympathy. It sounds like you've been doing your part in presenting the problem to the dealer(s)!!

I would expect, but do not know, that there would be a portable diagnostic tool you could drive around with to collect data. That might be quite helpful.

Other than that, it must be frustrating to know that with all the wires and solid state voodoo in these cars, an answer wouldn't be apparent.

While their offer of a $4K credit sounds "sincere", I'm guessing it falls under the "fool me once, shame on me" heading!!!!

Maybe the "Affordable Care Act" will expand from health "care" to vehicle warranties soon to attract more victims customers??

Good luck.
 

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50pascals said:
Specifically:
Engine Load goes rapidly to 100% and stays there (even though speed, throttle position and grade are unchanged)
Engine load absolute goes to 109%
Throttle Position Manifold goes to 83% (which is essentially pegged) even though I have not pressed the pedal any harder
Volumetric Efficiency (Calculated) goes very high
Fuel Flow goes high, in a very non-linear relationship

In laymens terms, it seems like the fuel flow is not right (likely high) the throttle is not open, so it runs rich, rough, bucks, and is essentially trying to stall.
Sounds like maybe a computer issue. What component controls the throttle position and fuel flow? Can the dealer change it out and see if that fixes it?
 

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It could be the MAF sensor. If the sensor reads inaccurate flow, then the rest of the fuel scheduling, etc., will be off.

Also, and this is not a root cause, rather an FYI, does the transmission have the latest programming? Since the transmission was rebuilt, I'd assume so, but they may have just maintained the same program from before. You'll know you have the latest programming if at 40 mph, it holds a constant 2000 rpm on level road. Only when you hit about 43 mph, will the transmission shift to 5th. If the rpm is lower at 40 mph than 2000 rpm, you have the old programming. Getting a re-flash might indirectly help.
 

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We had the same problem. I thought it was the tranny - but it was the coil on cyl #4. I know you said it's not the coils - but your problem sounds EXACTLY like the problem we had... replacing the coil fixed the problem.

Best of luck! We've had our own issues with our '09... thank GOD for the extended warranty.
 

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Discussion Starter · #6 ·
Thanks for the info on the transmission. I will check that this weekend for sure.

I found one post on here that mentioned fuel injector cleaner, and I will also be trying that this weekend.

I am also thinking it is computer or sensor related.

The MAF signal appears to track in a correct relationship to RPM, so I suspect the MAF is OK.

And I have a feeling it is related to the throttle pedal or throttle position sensor as it seems to only do this where the pedal would have spent most of it's life. The fact that a calculation pegs or a signal pegs is the big indicator. For example, if your fuel guage loses it's ground it will always peg to empty or full, depending on the type of sensor. Whatever mechanism it is that measures throttle position would have spent 99% of it's life right where we have the problem.

I do wonder more about what other signals should be going haywire if it is too much fuel.

And how bad would a fuel injector have to leak before it would set a code.

Regarding the dealer - they did everything they could do working within "the system" set up by GM. When I opened my service case they told me that this would now open other avenues for the delaer to get technical assistance, diagnostic time, etc. But their response (as well as the district rep) was

"your truck has a lot of miles, it's so hard to find these things, it gets very expensive, it would be much more cost effective to just buy a new vehicle."

The reason it is cost effective is that it shifts the cost back to me. Instead of eating some labor to try and actually diagnose a problem, they just want me to assume $20k more in debt, add 2 1/2 more years to my car payments, and downgrade from an LTZ to an LT - hopefully with leather. To keep the payment where we want it.

A friend owns a local repair shop, he has another customer with the same issue just developing (68k miles) I am going to try and drive her truck this weekend to data log it.

He also has the $10,000 Snap On handheld computer that can data log, etc. So I may teach myself how to use that too.

The most frustrating thing is that I know darn well this is not the first time Chevy has encountered this!
 

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Discussion Starter · #7 ·
ltzman said:
We had the same problem. I thought it was the tranny - but it was the coil on cyl #4. I know you said it's not the coils - but your problem sounds EXACTLY like the problem we had... replacing the coil fixed the problem.

Best of luck! We've had our own issues with our '09... thank GOD for the extended warranty.
So you also had no codes? That seems to be the big deal here. I am debating changing the coils anyways just to eliminate.
 

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You will only get a code on missfires if it goes over a threshold on a single trip - the counter is reset each time you turn the engine off and on (as far as triggering a missfire code).

It sounds like you have the OBDII adapter and torque - do you have the extra code package that lets you see the cylinder missfire counts? You can check these and see if any of them are getting large amounts of missfires - that will give you a clue.

Outside of that - when this happens - do you get a vibration along with a slight rev to your RPMs? I had that and it was the torque converter - your dealer should have a computer they can hook up to the car while doing a test drive - the system *they* have has the ability to turn the torque converter completely off while in drive - but only while the computer is hooked up - if it's the converter they can confirm that by flipping the toggle to turn off when it's happening - on my vehicle it went from rough to smooth with a flip of a switch.
 

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I was surprissed to read they offered you $4,000 !!!

Others on here have been offered some small amounts. (I think at most 2000?)..

But you said- its at 100,000.
You bought it used.. so you wouldnt 'lose' alot like if you had bought new (you still owe on the vehicle?)

I just looked up the trade in Value for an LTZ in my area and its about $14,000 (have they made a trade in offer?)

If I was in your situation-
I would consider trading it in... and using the $4000.

And either finding a leftover 2013...
OR getting a 2014..... I would consider at most a 2LT...
But most likely a 1LT... to keep cost low.

Youd have a new- 0 miles car....
and the rest-- pay off in a few yrs.
 

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Discussion Starter · #10 ·
nierd said:
You will only get a code on missfires if it goes over a threshold on a single trip - the counter is reset each time you turn the engine off and on (as far as triggering a missfire code).

It sounds like you have the OBDII adapter and torque - do you have the extra code package that lets you see the cylinder missfire counts? You can check these and see if any of them are getting large amounts of missfires - that will give you a clue.

Outside of that - when this happens - do you get a vibration along with a slight rev to your RPMs? I had that and it was the torque converter - your dealer should have a computer they can hook up to the car while doing a test drive - the system *they* have has the ability to turn the torque converter completely off while in drive - but only while the computer is hooked up - if it's the converter they can confirm that by flipping the toggle to turn off when it's happening - on my vehicle it went from rough to smooth with a flip of a switch.
I do use Torque, and will buy the extended version to check the counts.

I do get a vibration, which I had attributed to the engine running rough due to fuel or other engine management issues. I am a bit confused about the "torque converter" thing, as this is an automated manual gearbox. It has a clutch that is computer controlled. The only thing I think of is that a "torque converter" function may be the way they manipulate the clutch to simulate sensations to the driver.

rbarrios said:
I was surprissed to read they offered you $4,000 !!!

Others on here have been offered some small amounts. (I think at most 2000?)..

But you said- its at 100,000.
You bought it used.. so you wouldnt 'lose' alot like if you had bought new (you still owe on the vehicle?)

I just looked up the trade in Value for an LTZ in my area and its about $14,000 (have they made a trade in offer?)

If I was in your situation-
I would consider trading it in... and using the $4000.

And either finding a leftover 2013...
OR getting a 2014..... I would consider at most a 2LT...
But most likely a 1LT... to keep cost low.

Youd have a new- 0 miles car....
and the rest-- pay off in a few yrs.

Yes, we still owe on the vehicle as it was only bought in June 2012. I am not against the idea os getting a new LTZ. In fact, I want to get an Audi Q7 diesel. Cost or payment is not a primary concern.

What I was more focused on is the fact that we tend to own vehicles until their value is extremely low. As long as it is straight and shiny, I don't care. between my own shop and two friends repair businesses I keep the maintenance costs extremely low relative to what others have to pay. I get wholesale pricing on all my parts, and if I do not do the work myself, I get discounted pricing. So I buy a car (any car) with the understanding that I will own it for 4 to 8 years essentially for free. Before this Traverse we had no car payments for almost 10 years.

Beyond the "free ownership" period, the thing that really bugs me is that I am expected to take on additional debt to help GM out of a problem. Particularly one that they appear to be powerless to diagnose.

And yes, we are considering the new Traverse. I have given them my criteria for options and payment. I expect to hear back on my trade-in value today. This does appear to be the best deal we will ever get on a new car.

It's good to hear they offered me a healthy voucher.
 

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If you have Torque Pro (the one that costs money) you can add another app from the same developer called "TorqueScan" - this adds the extended OBDII codes - once you do that when you open Torque you'll have a 'magnifying glass' on the menu called Torque Scan - click that and let it read the values (it takes a few minutes for me) - wait until it says 100% done at *least* once because the missfire codes won't show up until it's scanned them - once it's on a second (or more) pass you can scroll down to see the missfire data.

The 2009 Traverse *has* a torque converter - it's a PITA to replace too ( they have to take the transmission off and support the engine to get at it) - it's a doughnut shaped thing that converts the engine power to the transaxle.

Here is a picture:






And this is the transmission with it removed (you can see where it sits)

 

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I am also thinking it is computer or sensor related.

The MAF signal appears to track in a correct relationship to RPM, so I suspect the MAF is OK.

And I have a feeling it is related to the throttle pedal or throttle position sensor as it seems to only do this where the pedal would have spent most of it's life. The fact that a calculation pegs or a signal pegs is the big indicator. For example, if your fuel guage loses it's ground it will always peg to empty or full, depending on the type of sensor. Whatever mechanism it is that measures throttle position would have spent 99% of it's life right where we have the problem.

I do wonder more about what other signals should be going haywire if it is too much fuel.

To me this screams "intermittent electrical failure". Maybe a cracked circuit board or cold solder joint in an electronic component. Or a "tin whisker" growing and shorting something out. Maybe there is a resonant vibration at this condition that causes a gap to open. Cheap to fix if you can find it, but for most people it's easier to buy a new box.


Regarding the dealer - they did everything they could do working within "the system" set up by GM. When I opened my service case they told me that this would now open other avenues for the delaer to get technical assistance, diagnostic time, etc.

Of course. And they conveniently steered you to labor-intensive jobs like the tranny rebuild and timing chain replacment which let their mechanics bill lots of expensive hours...


Maybe an independent shop would let you experiment with swapping electronic boxes until you found the one causing the problem?
 

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Discussion Starter · #13 ·
@nierd

I am very familiar with automatic trannys (the "doughnut" reference). But I had read somewhere this was a dry clutch automated gearbox jointly designed by Ford and GM.

Interesting that the RPMs will show a real clean shift - not even a millisecond of rpm drift. Please tell, why is it I can feel the clutch - particularly when trying to back up a hill or slight grade?

This torque converter thing could be a big deal, as it seems the ECU kills the fuel during a shift. The exhaust has that telltale sound. A few fuel kills, churning TC just before a shift, would certainly lead to a misfire.

I had two Volkswagens with the gas engine and DSG, the exhaust made the exact same burble the Traverse does on a shift. I now have a TDI and can't really hear the exhaust (unfortunately).
 

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Discussion Starter · #14 ·
So I am digging deeper into my log file and I see some real swings in O2 sensor signals when this happens.

Is there anyone on here that could look at this file and help determine cause / effect?
 

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I don't have answers for you - I just wanted to let you know from experience that the torque converter can cause odd hesitation/shifting/vibration/and bucking issues that don't throw a code (and the engine actually performs fine) - because your problem is currently 'unknown' I was hoping it would help as all the signs from my problem were missfire indicative until I put torque on it and read the missfire counts (showing an occasional 1-4 on startup) making me dig deeper.
 

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Discussion Starter · #16 ·
I now have torque pro and torque scan. I just sifted through it quick and did not see the misfire counts, but I will look again.

You know, the decision matrix for this seems pretty simple:

Does vehicle drive rough / hesitate / buck at highway speeds? Yes

Does the tachomter increase in rpm a little bit while this happens? Yes = Torque converter, No = coil packs

Perhaps I oversimplify. But from what I have now learned via the internet the above will lead you to the correct answer 90% of the time.

It's kind of sad that in this day a lockup torque converter would fail. This sounds like something out of the 80's. I have had several cars in the last two decades that were automatics and did not have lockup TC failure. Many of them with way over 100K on the clock. And a rough life to boot!

And this "no codes = nothing we can do" mentality - pathetic.

I'm going to drive the truck on my commute tomorrow (1 hour each way) I will be paying much more attention to the scans.

Also, bought 6 coils, 6 plugs, whatever gasket is needed, etc. Going to replace it all this Saturday.
 

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50pascals said:
I now have torque pro and torque scan. I just sifted through it quick and did not see the misfire counts, but I will look again.

You know, the decision matrix for this seems pretty simple:

Does vehicle drive rough / hesitate / buck at highway speeds? Yes

Does the tachomter increase in rpm a little bit while this happens? Yes = Torque converter, No = coil packs

Perhaps I oversimplify. But from what I have now learned via the internet the above will lead you to the correct answer 90% of the time.

It's kind of sad that in this day a lockup torque converter would fail. This sounds like something out of the 80's. I have had several cars in the last two decades that were automatics and did not have lockup TC failure. Many of them with way over 100K on the clock. And a rough life to boot!

And this "no codes = nothing we can do" mentality - pathetic.

I'm going to drive the truck on my commute tomorrow (1 hour each way) I will be paying much more attention to the scans.

Also, bought 6 coils, 6 plugs, whatever gasket is needed, etc. Going to replace it all this Saturday.
"And this "no codes = nothing we can do" mentality - pathetic"

To avoid being "pathetic", I guess the dealer could just throw parts at the car .... at the factory or owners expense, as you are doing. Something is bound to work, right?
 

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"And this "no codes = nothing we can do" mentality - pathetic"

To avoid being "pathetic", I guess the dealer could just throw parts at the car .... at the factory or owners expense, as you are doing. Something is bound to work, right?
I think 50 has point, Bob. So much is becoming computerized that the mechanics really CAN'T troubleshoot anymore without codes. I think part of it is probably lack of mechanic experience back to GM for use in training the mechanics. If some dealer actually had "thrown parts" at someone's car until they fixed it, and then TOLD GM what solved the problem so they could inform other mechanics, then all the mechanics troubleshooting acumen would increase and the next guy wouldn't need to have parts thrown at him. I can't say I know much about GM's feedback loop, but based on all the threads I've read on this forum the last 2 years, it doesn't seem very robust to me.
 

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greentraverse said:
I think 50 has point, Bob. So much is becoming computerized that the mechanics really CAN'T troubleshoot anymore without codes. I think part of it is probably lack of mechanic experience back to GM for use in training the mechanics. If some dealer actually had "thrown parts" at someone's car until they fixed it, and then TOLD GM what solved the problem so they could inform other mechanics, then all the mechanics troubleshooting acumen would increase and the next guy wouldn't need to have parts thrown at him. I can't say I know much about GM's feedback loop, but based on all the threads I've read on this forum the last 2 years, it doesn't seem very robust to me.
Yes, I agree that the computerization, to the degree to which we see today, can be very helpful or not so helpful to the ultimate solution of a problem.

Sound diagnostic practices, with common sense attached, have fallen victim to the rolling computers and codes the government & engineers have incorporated into our vehicles.

Implementing and continuing technician training is the ongoing responsibility of the individual dealer, but is always insisted upon by GM.

Correct diagnosis by the technician is paramount ...... and when all else fails, GM has the finest technical assistance program, in place, when the technician is "stumped". FYI, GM does have a feedback program in place, from dealership tech back to GM, which then fills the technical pool of info the technical folks provide back to dealership techs.

Piling on parts is my BIG objection .... and would be any ones' objection, if they were footing the tab for "maybe this or maybe that". There is a marked difference between "parts replacers" and "technicians".

"Maybe this or maybe that" doesn't fly when the overpayment of parts and labor is coming out of your own pocket OR the pocket of GM Warranty dollars.

Those unnecessary "warranty dollars" spent this year will cost all who purchase a new vehicle next year.
 
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