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2009 Cadillac SRX 3.6l shudder

  • fudgie
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02 Aug 2019 17:25 #32373 by fudgie
2009 Cadillac SRX 3.6l shudder was created by fudgie
Hello everybody-
My 2009 Cadillac srx is starting to frustrate me. Light throttle around 45mph (15-1800 rpm) and I get this very erratic misfire/ surge feeling. Idle and wot no issues. Has 96000 miles on it. No codes in any module. No misfires being detected. Mode 06 data gave 6 counts on cylinder number 1 and that's it. I had never looked at plugs- when I checked they were OE and toast. AC plugs and Delphi coils were installed just because it was foolish not too. Problem remains with no improvement. When this behavior happens- the rpm's don't seem to rise, so I figured probably not a TC lock-up issue (correct me if i'm wrong). Get it to downshift and problem gone. Fuel trims are spot on and the thing runs great at every other point. Mode 6 data on the chains look ok as well. Any thoughts would be appreciated. Thanks!

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  • Chad
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02 Aug 2019 18:30 #32374 by Chad
Replied by Chad on topic 2009 Cadillac SRX 3.6l shudder
Given that it is speed related, with no mis-fires or RPM change, I would look into the possibility of a wheel balance/bent rim.

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02 Aug 2019 18:47 - 02 Aug 2019 18:48 #32376 by Tutti57
Replied by Tutti57 on topic 2009 Cadillac SRX 3.6l shudder
Makes me think of rotational issues too. This reminds me of recently helping a friend, chasing my tail and it ended up being binding u joints.

Carrier bearing?

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Last edit: 02 Aug 2019 18:48 by Tutti57.

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02 Aug 2019 18:58 #32377 by fudgie
Replied by fudgie on topic 2009 Cadillac SRX 3.6l shudder
Thanks guys-
I wish it was a rim! I can make it happen. When it does- its a buck feeling. Coffee slosh around... "whats that" from the wife. Step on the pedal a little harder and its gone. I would have bet my paycheck I would see misfire counts go nuts- but that's not the case. The counters have never moved once. When I see this type of symptom, being the rpm range and load it happens in- it has always seemed to point to a coil breaking up. Thanks for the input!

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  • Tyler
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02 Aug 2019 21:30 #32388 by Tyler
Replied by Tyler on topic 2009 Cadillac SRX 3.6l shudder
I actually strongly suspect a TCC issue. :lol: You're describing the exact speed and load that I typically see these clutches shudder. Forcing the downshift changes TCC pressure and makes the shudder disappear.

GM seems to be especially hard on their TCCs. They employ a variable pressure strategy, and intentionally 'slip' them even during engagement. They have far more TCC issues than any other make, IMO.

Depending on which scan tool you have available, you can command the TCC off and recheck for the issue. If it's gone, you know where the issue is. If not, proceed with further testing.

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03 Aug 2019 09:39 #32410 by fudgie
Replied by fudgie on topic 2009 Cadillac SRX 3.6l shudder
I looked at tcc info with my little launch. I get tcc duty cycle and and slip percentage only. I start a new job Monday so I will have access to my tools and other scanner. 21 years at independent shop and owner retiring. Tried to buy- but waaay to much $$. A story for another day. Thanks for the info guys. Appreciate the help

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03 Aug 2019 09:50 #32411 by Noah
Replied by Noah on topic 2009 Cadillac SRX 3.6l shudder
If it is TCC related, would tapping the brake pedal with your left foot make it stop? Brake pedal switch input is generally cancels TCC engagement.

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03 Aug 2019 14:03 #32424 by Tyler
Replied by Tyler on topic 2009 Cadillac SRX 3.6l shudder

Noah wrote: If it is TCC related, would tapping the brake pedal with your left foot make it stop? Brake pedal switch input is generally cancels TCC engagement.


Maybe? :silly: Many newer GM's I've seen don't kill the TCC with brake application, like we're used to.
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04 Aug 2019 11:57 #32470 by Tutti57
Replied by Tutti57 on topic 2009 Cadillac SRX 3.6l shudder
what inputs do they use to disengage, engine/vehicle speed?

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04 Aug 2019 12:58 #32472 by Tyler
Replied by Tyler on topic 2009 Cadillac SRX 3.6l shudder
Let me rephrase - I'm sure the TCM does look at the brake switch as part of it's strategy. But I've found that the brake switch and TCC application are not exactly correlated. Like this example from an '11 Yukon. The brake switch got tapped, but the TCC stayed engaged:




Other times, you can see a delayed reaction to brake application:




This is why I don't completely rely on the brake switch trick any more. :silly:
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04 Aug 2019 18:42 #32482 by fudgie
Replied by fudgie on topic 2009 Cadillac SRX 3.6l shudder
Thanks everybody. I attempted to tap the brake and it didn't seem to help. I have a snap-on scanner in my box. I will see if I can temporarily disable the lock-up function and report back.

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05 Aug 2019 21:52 #32526 by Noah
Replied by Noah on topic 2009 Cadillac SRX 3.6l shudder
Good information as always Tyler, thank you!

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