Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
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!
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.
"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer." I have learned more by being wrong, than I have by being right.
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!
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.
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
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.
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:
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.
