I'm not sure if this is a sparkplug issue or something else
10-14-2018, 02:33 PM
#11
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Join Date: 12-30-2016
Location: Cobleskill, NY
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Yeah I'm sorry it's so vague, I don't know a lot about this stuff. Usually when I'm cruising right below 40mph and I press the accelerator, that's my best bet to make it happen. It feels like a slight jump forward, and then it settles out. Again, doesn't always happen. No codes, throttle body is clean. 73k miles so the spark plugs *should* be fine, and I can't possibly imagine it's the transmission this soon. I hope not, anyway..
10-14-2018, 05:18 PM
#12
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Location: Fredericksburg, Virginia
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Kind of like the transmission down shifting? It is a 4 speed overdrive, but the torque converter also has a clutch.
So at 40 it just got to "cruising" (4 th gear and TC locked) then you ask for accel, The TC unlocks and might down shift, depending on your demand
40 mph is right at the indecision point..
So at 40 it just got to "cruising" (4 th gear and TC locked) then you ask for accel, The TC unlocks and might down shift, depending on your demand
40 mph is right at the indecision point..
10-14-2018, 05:37 PM
#13
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Join Date: 12-30-2016
Location: Cobleskill, NY
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Kind of like the transmission down shifting? It is a 4 speed overdrive, but the torque converter also has a clutch.
So at 40 it just got to "cruising" (4 th gear and TC locked) then you ask for accel, The TC unlocks and might down shift, depending on your demand
40 mph is right at the indecision point..
So at 40 it just got to "cruising" (4 th gear and TC locked) then you ask for accel, The TC unlocks and might down shift, depending on your demand
40 mph is right at the indecision point..
10-14-2018, 06:32 PM
#14
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Join Date: 10-13-2011
Location: Welland,Ont Canada
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It’s called the 40 mph jounce for some reason.
earlier years had to have their TCM’s reflashed.
Its really harmless just a PITA, because we are so alert to abnormal shifts and well , it’s normal.
vintage reading
https://www.chevyhhr.net/forums/2-4l...ar-auto-47421/
earlier years had to have their TCM’s reflashed.
Its really harmless just a PITA, because we are so alert to abnormal shifts and well , it’s normal.
vintage reading
https://www.chevyhhr.net/forums/2-4l...ar-auto-47421/
10-14-2018, 06:39 PM
#15
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Join Date: 12-30-2016
Location: Cobleskill, NY
Posts: 136
It’s called the 40 mph jounce for some reason.
earlier years had to have their TCM’s reflashed.
Its really harmless just a PITA, because we are so alert to abnormal shifts and well , it’s normal.
vintage reading
https://www.chevyhhr.net/forums/2-4l...ar-auto-47421/
earlier years had to have their TCM’s reflashed.
Its really harmless just a PITA, because we are so alert to abnormal shifts and well , it’s normal.
vintage reading
https://www.chevyhhr.net/forums/2-4l...ar-auto-47421/
You know what it is? I used to have a sunfire that died when I had to change the starter. After I got the new part it, the engine wouldn't turn over. Before anything had happened to the starter, I was getting trash compression, and my engine would stall out when idling, and just flat out get stuck in low gears when accelerating. Around the same speed, that car's engine would noticeably cut out for a second. So when I (randomly) started noticing this "jounce" as you called it, it brought up some ptsd for my old sunfire.
10-15-2018, 05:31 AM
#17
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10-15-2018, 05:46 PM
#18
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Don’t depend on luck and sensors, pop off the valve cover and look at the timing chain, any time after 100,000 miles, I would consider changing the chains as preventative maintenance.
But I’m old school, and Inhate waiting for a tow truck.
But I’m old school, and Inhate waiting for a tow truck.
10-15-2018, 07:40 PM
#19
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10-15-2018, 08:56 PM
#20
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Join Date: 12-30-2016
Location: Cobleskill, NY
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I'll definitely get a bunch of things serviced at 100k, but as for this particular whatever-is-happening, I can't really do much if the car isn't telling me something is wrong. It's completely drivable, and nothing else is happening.