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heat wave in jersey last week so definitely couldn't shut the AC off! haha serpentine and AC belt are new, so maybe the compressor is starting to show some age?

In the schematic i only see one ground cable, is this the only one?
Cable, Sub-Ground - Honda (32610-S9V-A00)
Not sure if this is the cable that bolts to the transmission. I'm sure someone knows it's exact location will post. Hopefully.
 

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So this is new information. Your car jerks (sometimes) when downshifting from 5th to 4th, AND it jerks on startup - but only with the AC on. Definitely odd.

I think I’d check motor mounts, drive shaft and then alternator. My thinking is you’re feeling that jerk when you get significant torque transfer, which happens at start up or most noticeable at the downshift from 5th to 4th (perhaps it’s only jerking when you’re braking hard, which is why it’ only erratic on the downshift?).

I also recall reading somewhere that reduced voltage output can disrupt normal shifting / and if it’s only happening with the AC on, perhaps you’ve got a big enough power drop that it’s affecting the tranny electronics? I think this would explain the problem at startup - no idea about 5th to 4th.

If it’s only happening in 1st and downshifting out of overdrive, then I can’t personally explain a bad ground strap causing this, because I would anticipate a bad strap to cause a problem in any gear when the car is shifting or any time you hit a bad bump (etc). But - ground strap is easy to check …
 

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Not sure if this is the cable that bolts to the transmission. I'm sure someone knows it's exact location will post. Hopefully.
Would this diagram for a 2006 be close enough?
 

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Discussion Starter · #26 ·
so interesting ending to this issue.. figured id fill you guys in.
decided to take it to a transmission shop, and both guys weren't convinced if it was a misfire or torque converter.
Decided to order plugs and see what happened.

Ordered NGK plugs and swapped all 6 of them, with 50K miles on them.
When removing the old plugs (NGK as well), i did notice that they weren't as tight as i thought they should be.
Measured gap of all 6 plugs? .080"! Now i installed myself and know that i gapped them all to .040", so I was surprised.
To be fair, I don't remember if I used a torque wrench to install the last time, due to the tight area, but this time I did.

Test drive, and issue is gone, and she's pulling great throughout the power band!
Surprise ending, never seen gaps grow that big, but maybe the plugs were a little lose? regardless, she's back on the road and aiming for 300K miles!

Appreciate all the support and insight.
Drinkware Product Gas Cylinder Lens
 

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Glad you got it fixed, and for less than it could have been.

And thanks for adding your data point as a reminder that occasionally retorquing spark plugs to spec should be considered a maintenance item on these vehicles.

Found one oddity when changing plugs.

Spark plug #4 and #2 backed out


 

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So just to be clear / you were running those plugs that were gapped at almost 2x recommended tolerance, your CEL wasn’t lit and there were no stored nor pending codes?

Slvr7 - do you see this often where loose plugs this bad don’t throw misfire codes?
 

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So just to be clear / you were running those plugs that were gapped at almost 2x recommended tolerance, your CEL wasn’t lit and there were no stored nor pending codes?

Slvr7 - do you see this often where loose plugs this bad don’t throw misfire codes?
There wasn't and codes due to the low number of misses. There has to be x number of misses in x number of seconds, threshold wasn't met.
I don't see it a lot but learned from getting my butt kicked by it early in my career. I don't think I have ever seen a loose plug cause a miss, normally there is a noise attributed to it. On a j motor, to me, it mimics a loose valve at first, then a rod knock at about 1.5 turns out.
Most people think highest load seen by the cylinder is during wot at higher rpm. It's not, highest is at around 40-50mph with the converter locked while tipping in throttle, but not enough to unlock the converter. I'm guessing that's what the op was experiencing. 40ish in 4th gear, slightly more throttle enough to induce the downshift, but not to unlock the converter.
 

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Discussion Starter · #31 ·
There wasn't and codes due to the low number of misses. There has to be x number of misses in x number of seconds, threshold wasn't met.
I don't see it a lot but learned from getting my butt kicked by it early in my career. I don't think I have ever seen a loose plug cause a miss, normally there is a noise attributed to it. On a j motor, to me, it mimics a loose valve at first, then a rod knock at about 1.5 turns out.
Most people think highest load seen by the cylinder is during wot at higher rpm. It's not, highest is at around 40-50mph with the converter locked while tipping in throttle, but not enough to unlock the converter. I'm guessing that's what the op was experiencing. 40ish in 4th gear, slightly more throttle enough to induce the downshift, but not to unlock the converter.
this is exactly when the issue would peak.. tipping in the throttle but not enough to kick it out of overdrive.
have you seen plugs go from .040 to .080? first for me
 

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Discussion Starter · #32 ·
So just to be clear / you were running those plugs that were gapped at almost 2x recommended tolerance, your CEL wasn’t lit and there were no stored nor pending codes?

Slvr7 - do you see this often where loose plugs this bad don’t throw misfire codes?
Correct. originally gapped to .040, went to .080 and no codes, nor pending codes.
 

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Correct. originally gapped to .040, went to .080 and no codes, nor pending codes.
Perhaps it's just me, but the grounding prong/electrode seems fine whereas the center electrode looks very worn down on your old plugs. If I'm reading the code on the side of the plug correctly, those are also NGK copper plugs - that may be part of the reason for the excessive wear at 50k (compared to the 100k usually stated for platinum or iridium).
 

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Perhaps it's just me, but the grounding prong/electrode seems fine whereas the center electrode looks very worn down on your old plugs. If I'm reading the code on the side of the plug correctly, those are also NGK copper plugs - that may be part of the reason for the excessive wear at 50k (compared to the 100k usually stated for platinum or iridium).
Agree.
They were definitely not NGK Laser Iridiums.
 

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I wanted to also mention to anyone wanting to re-gap a fine wire Laser Iridium spark plug. You can not pry on the center fine wire electrode. They will break. Requires a special tool.
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Factory plugs were NGK Platinum.
The electrode on the old plug looks like that from a conventional plug.
The one on a (new) platinum plug would look like this:

View attachment 152774
Oops, sorry, for some reason I was thinking 08. Thanks for the correction.
Some other better choices would be..
Denso Long Life Iridium
NGK Ruthenium HX
 
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