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2010 CTS
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Discussion Starter #1
My 2010 CTS AWD with 3.6L DI (56,000 miles) has what seems to be a misfire on hard acceleration. I can feel slight stumbles or misfires during acceleration - - it actually feels to the seat of my pants like multiple automatic transmission shift points (but that's not what it is, as indicated by the gear display in sport mode). No check engine light, and I checked for codes and found no codes stored in the ECU. This has me wondering if it's actually a misfire or something else. My question is, "Are all misfires logged by the ECU and appear as a fault code?"

The lack of a code has me wondering if it's something else. Is it possible that an issue with the transmission, AWD, or traction control could cause similar symptoms? I did check and the stumbling occurs at least in 2nd, 3rd and 4th gear. Kind of hard to avoid downshifting at least to 4th under hard acceleration. I also checked and the symptom does occur with the traction control turned off.

I added a bottle of Techron to clean the injectors to no avail.

I do intend as the next step to change the plugs and inspect the coils for arcing. But the lack of codes gives me pause. Any comments or advice is greatly appreciated! Thanks!
 

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05 srx awd v6 (gone), '07 GXP, 2010 li'l red wagon 3.6
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A DTC only sets when the misfire rate is sufficient to cause excessive emissions. An occasional stumble won't do it.
 

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2013 Black Diamond CTS4 Premium Coupe (sold-09 CTS4 DI Black Raven/Ebony)
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and when I had the occasional misfires, I thought it was the trans. Felt like a trans slip. but plugs solved the problem.
 

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'14 CTS-V LongRoof; '16 ATS-V Sedan,' 04 Trailblazer 4x4; '10 CTS LongRoof gone but never forgotten
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Mine has been stumbling a little, but no codes.
 

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2010 CTS
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Discussion Starter #5
Thanks everyone for the replies. I changed the plugs and it made no difference. There was no sign of any problem with any of the coils. Any ideas as to what to look for next?
 

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2008 SRX4 & 2010 CTS4 sedan / Non-Cadillacs: 2018 Audi Q5, 2012 Chev Cruze LT
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327 Posts
Resurrecting this - in the spirit of Lazarus...

This is the symptom experienced regularly over the last two months:

Slight stumble under medium throttle. Comes and goes and lasts only a few seconds. Appears mostly in upper gears but not when holding speed or at the point of a gear change - just while accelerating and not under light acceleration or WOT. The car just feels like something is stumbling.

New plugs last year, original coils, valves are untouched (never done the walnut blasting). No codes whatsoever and no MIL. Have added Techron about once a year for the past few years and pretty well religiously buy top tier gas.

Suspect fuel pump. Hope it's not a slipping torque converter but I am not sure that I would know what that feels like as I've never personally experienced it.
 

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08 CTS DI
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2,086 Posts
I would suspect an ignition coil since it's happening mainly under load when the resistance to the spark jumping the plug gap increases. It can still be a plug also. You can start by inspecting them. You might find that a tube is contaminated with engine oil which can also interfere with ignition. If by chance you have the old plugs, which I'm sure you don't, you can close the spark plug gaps down on them by half and try them. That makes it easier to generate a spark in the gap and if it resolves the problem would still point to either a plug, or coil. Sometime it is necessary to close the plug gap on boosted cars as the boost is increased to counter misfires that sometimes develop as a result of the increased resistance in the plug gap from the denser air charge. A weak ignition spark would respond the same way.

You know what to do to rule out the fuel pump and a slipping torque converter would slip like a clutch rather than stumble. If the problem was at throttle tip in I would include the throttle body as a possibility.
 

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2008 SRX4 & 2010 CTS4 sedan / Non-Cadillacs: 2018 Audi Q5, 2012 Chev Cruze LT
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I would suspect an ignition coil since it's happening mainly under load when the resistance to the spark jumping the plug gap increases. It can still be a plug also. You can start by inspecting them. You might find that a tube is contaminated with engine oil which can also interfere with ignition. If by chance you have the old plugs, which I'm sure you don't, you can close the spark plug gaps down on them by half and try them. That makes it easier to generate a spark in the gap and if it resolves the problem would still point to either a plug, or coil. Sometime it is necessary to close the plug gap on boosted cars as the boost is increased to counter misfires that sometimes develop as a result of the increased resistance in the plug gap from the denser air charge. A weak ignition spark would respond the same way.

You know what to do to rule out the fuel pump and a slipping torque converter would slip like a clutch rather than stumble. If the problem was at throttle tip in I would include the throttle body as a possibility.
Thanks Joseph. I am honing in on an ignition issue. I will look at the valve cover gasket this weekend as I know that these are problematic and oil can seep into the spark plug pit. I kept the old plugs because - even after 100,000+ miles, they looked almost new. I will start with inspecting the plugs - I have a hunch that the right side bank might be the culprit.

I've had a clutch go out on me before (waaaay back in the late 70s) and that car lurched a bit until it basically couldn't hold a hill very well. This is not even remotely similar to that so I will eliminate (for now) any thought that this is tranny related.

I will post here what I find.

Thanks again.
 

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08 CTS DI
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I kept the old plugs because - even after 100,000+ miles, they looked almost new.
You must have known this was coming. The precious metals plug tip (iridium) is sensitive and it is recommended that they not be gapped because of the risk of damaging and even removing the coating from the tip which would shorten plug life, that's why I suggested the old plugs instead of the new to experiment on.

You're over a 100k so unless you've replaced them already, you know the "chain gang" can cause problems without setting a code. I just read up on a 2015 LFX swap into a Miata with about 15k miles on the motor that dropped a chain from one bank while being tracked, although I and the owner agree that it was probably the result of a brief period of extremely high coolant temps ~260ish before exiting the track. It was on low turbo boost ~7 psi, and started misfiring a bit on another outing before letting go. High heat = thin oil and engine oil runs a lot hotter than the coolant temp.

I didn't get to see pictures, but apparently the elongating chain resulted in cylinder temps so lean that only two of the three plugs could be worked out of the cylinder head, the middle plug broke off. This is additional proof positive for me that as I've said before, these motors are hard on engine oil and can definitely benefit from a good flow of cool oil from the actuators and probably a bump in oil viscosity in addition to sane oil change intervals.
 

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2012 CTS4 Premium
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I had a similar experience with my 2012 Cts 3.6 awd coupe about a year ago. Then one day it threw a flashing check engine light. That ended up being a bad coil pack of the first cylinder. Coincidentally that issue seemed to go away after that repair. I can’t be sure they are related. But thought I’d throw that experience out there.
 

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2008 SRX4 & 2010 CTS4 sedan / Non-Cadillacs: 2018 Audi Q5, 2012 Chev Cruze LT
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You must have known this was coming. The precious metals plug tip (iridium) is sensitive and it is recommended that they not be gapped because of the risk of damaging and even removing the coating from the tip which would shorten plug life, that's why I suggested the old plugs instead of the new to experiment on.

You're over a 100k so unless you've replaced them already, you know the "chain gang" can cause problems without setting a code. I just read up on a 2015 LFX swap into a Miata with about 15k miles on the motor that dropped a chain from one bank while being tracked, although I and the owner agree that it was probably the result of a brief period of extremely high coolant temps ~260ish before exiting the track. It was on low turbo boost ~7 psi, and started misfiring a bit on another outing before letting go. High heat = thin oil and engine oil runs a lot hotter than the coolant temp.

I didn't get to see pictures, but apparently the elongating chain resulted in cylinder temps so lean that only two of the three plugs could be worked out of the cylinder head, the middle plug broke off. This is additional proof positive for me that as I've said before, these motors are hard on engine oil and can definitely benefit from a good flow of cool oil from the actuators and probably a bump in oil viscosity in addition to sane oil change intervals.
I should have added that my Caddy dealer replaced the timing chains in August 2018.

Interesting insights. I change the oil on the CTS and my kid's Cruze (turbo 1.4L) at roughly 6-7,000 km intervals (3-4k miles). For some reason, the 2008 SRX (3.6L but non-DI) seems easier on its oil. I only use OEM filters (bought in bulk from Rockauto) and always Mobil 1 5w30.

I am now suspecting oil in one of the plug pits is somehow interfering with the coil pack. That will be my first task this weekend.
 

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08 CTS DI
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One of the side effects from direct injection is a documented higher fuel contamination of the oil, so the LY7 probably isn't as as taxing on the oil, but having performed my own oil changes for the past 30 plus years, there's no doubt the oil comes out of my 3.6L looking pretty beat compared to what I have been used to.
 

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08 STS 1SG HUD ACC F55 AWD, 08 STS 1SG Platinum HUD ACC F55 RWD
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It is true that all misses will not necessarily set a code but a TechII and some other scanners will keep a running count of misses for each cylinder. TechII actually has a bar graph listing each cylinder. Blue driver just gives the miss count for this running of the engine and an average for the last 10 times the engine was run (again seperate values for each cylinder) This may help with your diagnosis and help focus on the specific problem area. Good Luck.
 

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I hesitate to post this as I had the same problem. I need to drive a little more to fully test it.

On my daily drive to work I could repeat the problem on 2 locations where I would get this hesitation. Almost like a shift in the tranny but no indication of a gear change. I even ran a snapon reader and I had 2 coils that had slight misfires after changing them out the problem persisted. I change to top tier 91+ fuel. nothing would stop it so I gave up and just drove it.

Last week I lost the magnet on the pass. side rear wheel bearing. After changing out the bearing I cannot get hesitation to repeat. I'm not 100% sure if this is the fix or not. In my mind if I had a small section of the mag ring missing or raised and this would most of the time not be an issue, but as engine load and vehicle speed increased maybe the computer would try to stop what it reading as wheel slip?

Thoughts?
 

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2008 SRX4 & 2010 CTS4 sedan / Non-Cadillacs: 2018 Audi Q5, 2012 Chev Cruze LT
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I hesitate to post this as I had the same problem. I need to drive a little more to fully test it.

On my daily drive to work I could repeat the problem on 2 locations where I would get this hesitation. Almost like a shift in the tranny but no indication of a gear change. I even ran a snapon reader and I had 2 coils that had slight misfires after changing them out the problem persisted. I change to top tier 91+ fuel. nothing would stop it so I gave up and just drove it.

Last week I lost the magnet on the pass. side rear wheel bearing. After changing out the bearing I cannot get hesitation to repeat. I'm not 100% sure if this is the fix or not. In my mind if I had a small section of the mag ring missing or raised and this would most of the time not be an issue, but as engine load and vehicle speed increased maybe the computer would try to stop what it reading as wheel slip?

Thoughts?
I gave that some thought a couple of weeks ago. All four bearings have been replaced on the CTS within the last 18 months so I doubt it's a failed magnetic ring. Also 3 out of the 4 sensors were replaced when the bearings were replaced. The fourth - the front right one - was in perfect shape visually so I left it in. But it could be failing inside. Weird if it was the case and I wasn't finding any codes.

I will drive the car today in competition mode and see if that makes a difference as, like you, there are a couple of locations where I always get this stumbling (both are flat roads, by the way). I will report back tonight.
 

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2008 SRX4 & 2010 CTS4 sedan / Non-Cadillacs: 2018 Audi Q5, 2012 Chev Cruze LT
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I hesitate to post this as I had the same problem. I need to drive a little more to fully test it.

On my daily drive to work I could repeat the problem on 2 locations where I would get this hesitation. Almost like a shift in the tranny but no indication of a gear change. I even ran a snapon reader and I had 2 coils that had slight misfires after changing them out the problem persisted. I change to top tier 91+ fuel. nothing would stop it so I gave up and just drove it.

Last week I lost the magnet on the pass. side rear wheel bearing. After changing out the bearing I cannot get hesitation to repeat. I'm not 100% sure if this is the fix or not. In my mind if I had a small section of the mag ring missing or raised and this would most of the time not be an issue, but as engine load and vehicle speed increased maybe the computer would try to stop what it reading as wheel slip?

Thoughts?
I drove today in competition mode and the stumbling did not occur where/when it normally does. I will try it one more day (tomorrow).
 

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'14 CTS-V LongRoof; '16 ATS-V Sedan,' 04 Trailblazer 4x4; '10 CTS LongRoof gone but never forgotten
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This sounds like the ultimate answer. First, your problem is fixed (we all hope) and second you'll have much more fun while driving!
 

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2011 CTS Coupe Premium
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OK folks, what you need to do it to run "standard test #6". It will give you the number of misfires on the last cycle and for the last ten cycles.

This is just the part for cyl 4 on my CTS.

MID:$a5 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 4 Data
Max: 65,535Count Min: 0Count
Test result value: 0Count
PASS
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MID:$a5 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 4 Data
Max: 65,535Count Min: 0Count
Test result value: 1Count
PASS

To read this costs a whole $16 if you have an Android phone or tab. $10.99 for a BT dongle and $4.99 for Torque Pro (current price may be different, cannot see). Been using for my cars with OBD-II and any new car I am considering for years.

And an additional thought on rereading the thread: if the computer is commanding a rediction in power for some reason, it will not record a misfire. Sometimes no news is informative.
 

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I drove in competition mode yesterday and the problem reoccurred. Either today or tomorrow, my blue driver's mode 6 test didn't come up with anything but I am game to try again today and then have a look-see into the spark plug wells.
 
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