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You could also try locking the timing at a certain ° and going for a test ride to see if the violent bucking goes away.

but just to clarify, is it a misfire or is it bucking at light load? Does the CEL come on?

stock cam?
Has anyone turned the throttle stop screw for any reason?
 

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Does it have a warm idle of 672rpm?
Your problem could be in the IAC duty cycle if not.
 

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I don't have a digital tach but warm idle was higher than that, just below 1000. So I found the instructions for the Professional Products throttle body and saw that their initial installation procedure, decided to follow it despite the fact that I have a stock throttle body.

I did this because I saw that the previous owner had adjusted it (by replacing the screw..)

After this I started the car and drove around the block to get it warmed up, then let it idle and it seems like probably around 700 based on needle position. Notably lower than before.
neither of those are adjustable without a competent tuner datalogging the values.
Some of the OEM throttle stop screws do have a phillips head on them.

And, when a tuner does adjust those, the car should be fully warmed up. With the IAC disconnected, the car should barely idle at around 500rpm (warm idle).

im fairly certain this is where your issues are coming from now. 1,000 rpm was too high, affecting the IAC duty cycle. The IAC also acts as a dashpot, stall prevention, cold idle increase, and idle load increase.

it has a transfer function of its own. Turning the bleed screw has completely skewed those airflow values.

that’s under the assumption that your 1,000 rpm wasn’t from a vacuum leak.
 

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Well, they weren’t correct to begin with if you had a 1,000 rpm idle 🤷🏻‍♂️
 

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What makes you think it’s “tense”?

I didn’t really see where anyone made it that way, IMO

it’s really difficult to get those parameters back in spec if you can’t see the data, best you can hope for is “close enough” to still allow the EEC enough room to do its thing.

at least you clarified that it wasn’t a misfire, which would take you down an entirely different path.
 
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