I'm sick...think my car is developing "The Stumble"
06-27-2017, 10:14 AM
#46
Burning Brakes
There is an extensive thread with a poll over at 6speed. I feel like it's been discussed quite extensively there. Still no solutions!
06-27-2017, 01:57 PM
#47
Could it be a failing Valve Lift Solenoid? I know I had one go bad on my car and it was stumbling and nearly stalling quite a bit when it was warmed up. https://rennlist.com/forums/991/8307...l#post14251115
06-28-2017, 10:29 PM
#48
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I notice the stumble in two instances:
1) Normal driving under light throttle. Around town, as I accelerate through ~2600 rpm I'll get it. Occurs probably 75% of the time. For some reason, it never occurs in 1st gear. Drive it aggressively and you'll never feel the slightest hesitation.
2) On an uphill grade, if I hold the rpm at or near 2600, I'll get a noticeable stumble. Imagine a micro second of bad fuel.
Chances are, if someone else were to drive my car, it would take a week or so for them to notice the problem. But once you know it's there, it's impossible to ignore.
1) Normal driving under light throttle. Around town, as I accelerate through ~2600 rpm I'll get it. Occurs probably 75% of the time. For some reason, it never occurs in 1st gear. Drive it aggressively and you'll never feel the slightest hesitation.
2) On an uphill grade, if I hold the rpm at or near 2600, I'll get a noticeable stumble. Imagine a micro second of bad fuel.
Chances are, if someone else were to drive my car, it would take a week or so for them to notice the problem. But once you know it's there, it's impossible to ignore.
06-29-2017, 09:50 AM
#51
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Originally Posted by jadoca
This best describes me until I replaced the OEM tires with the Michelin 4S. Stumble gone.
06-29-2017, 10:01 AM
#52
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He just forgot to use the sarcasm emoji 
Similarly to what others have mentioned here...
Just my unqualified recommendation... Additives are mostly snake oil IMHO but if I was going to try one it'd be lucas. You've been playing with cars a long time so likely you have your own point of view on this.
My "italian tune up" would consist of either some 93 Octane NON ETHANOL gas or a 1/4 tank mixture of 100 Octane gas and go for a 50 mile drive.
The key to this will be having a cigar and the top down of course.
Similarly to what others have mentioned here...
Just my unqualified recommendation... Additives are mostly snake oil IMHO but if I was going to try one it'd be lucas. You've been playing with cars a long time so likely you have your own point of view on this.
My "italian tune up" would consist of either some 93 Octane NON ETHANOL gas or a 1/4 tank mixture of 100 Octane gas and go for a 50 mile drive.
The key to this will be having a cigar and the top down of course.
06-29-2017, 11:04 AM
#53
Rennlist Member
The previous owner may have been a spirited driver, coupled with your wife learning to drive it and city driving that wears the clutch more I would say it is the clutch.
06-29-2017, 11:39 AM
#54
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06-29-2017, 02:17 PM
#55
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It's not the clutch. I detect zero slippage. I specifically put it in high load situations to test it. Nothing.
07-07-2017, 01:53 AM
#56
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I have a theory. My 2-3k rpm hesitation/stumble has come and gone (I've owned my car for 4.5 years since new and covered 27k miles, '13 c2s). I have noticed that the stumble comes during summer months and goes away in the colder months. My theory is that the stumble happens when the gas stations switch to Sumer fuel blend and goes away with switch to winter blend. I live in ny btw. Furthermore, I'm thinking that people in warm states are always on summer blend and therefore are stuck with constant stumble.
07-07-2017, 08:59 AM
#57
Burning Brakes
Ok, say I wanted to mix in some 100 octane with my normal 93 when I fill up. What are some recommendations? I see I can get Sunoco 260 GT 100 octane in a 5 gallon container near me.
07-07-2017, 11:03 AM
#58
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Originally Posted by SB
I have a theory. My 2-3k rpm hesitation/stumble has come and gone (I've owned my car for 4.5 years since new and covered 27k miles, '13 c2s). I have noticed that the stumble comes during summer months and goes away in the colder months. My theory is that the stumble happens when the gas stations switch to Sumer fuel blend and goes away with switch to winter blend. I live in ny btw. Furthermore, I'm thinking that people in warm states are always on summer blend and therefore are stuck with constant stumble.
07-07-2017, 11:14 AM
#59
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You can add as much 100 octane (make sure lead free and not over 10% ethanol) as you want and your billfold allows. Your car can accommodate it, but can't utilize and optimize the added octane without a tune. It will be mostly placebic. You may notice a very-very-very slight "improvement" up to about the average 96 level. Anything above that would be a complete waste. So, if you do a 1/2 tank 93 and a 1/2 tank 100 you will average out at about 96.5. Good luck with the experiment.
07-07-2017, 12:10 PM
#60
Rennlist Member
I have a theory. My 2-3k rpm hesitation/stumble has come and gone (I've owned my car for 4.5 years since new and covered 27k miles, '13 c2s). I have noticed that the stumble comes during summer months and goes away in the colder months. My theory is that the stumble happens when the gas stations switch to Sumer fuel blend and goes away with switch to winter blend. I live in ny btw. Furthermore, I'm thinking that people in warm states are always on summer blend and therefore are stuck with constant stumble.