bad jerking low throttle slow speeds.

[boback1]

i have a 416 ls3 with tfs 235 heads, holley 95mm throttle with low rpm taper, fast 102, cam has 21.5 degrees overlap. It's on an 02 camaro ss ecu tunes in SD. when i am in 1st or 2nd gear at 1600 to 2500 rpm coming around my parking garage the car will jerk violently, enough to bounce me out of my seat. I thought it was really bad cam surge but i can be at these same rpms on the freeway cruising and not feel really any cam surge. It only happens in 1st or 2nd gear trying to creep around my parking garage or in parking lots. happens around 1 to 2% throttle percentage. I have to clutch it to stop the shaking or give it a lot more throttle. I do know that my throttle plate is opened a good amount for idle. I had to max out the tps clocker on my holley throttle body to get the tps back in the .5v range. I've attached my current tune. Thank you.

[outoftune]

I'm working with that now. Great Video on YouTube by Trackstar Media works, (Heading)how to fix big cam surge... Watch entirety.
Match your High octane and low octane charts....Basically copy n paste high table into low.. Then all your 1200rpm ish to 2400rpm cells in the 10-30ish KPA cells(maybe wider or narrower range) reduce cells to 20 deg (good starting point) then blend in to adjoining cells for smooth transition.
Other discussions about injector timing....but the video doesn't show them make adjustments to that table.. big cam surge is very annoying it almost feels like you can break an input or output shaft on the transmission! Let us know how you make out.

[boback1]

Thank you for the video tip. I watched it and adjusted my timing in those areas and my bucking was about 40% less than what it was. still needs more but I'm afraid it might be down to the iacv and other adjustments with throttle follower and cracker. Just wanted someone to look over my tune and tell me if they see anything weird with the base running airflow or other settings with idle and throttle. I have a good friend who is a very great tuner and he tunes my car for free and on his spare time ( which he doesn't have a lot of ) so i let him handle the making power and making it stay alive and i'm trying to learn the time consuming drive ability issues. And your right about how violent the bucking is, feels like my engine is gonna jump out of my car lol.

[SydneyACE]

I'm having the same issue. Hopefully someone that knows stuff can help us out.

[anniversaryss]

Got a log? Cam specs?

[lukearmstrong1990]

your idle spark table in the 1600-2400 rpm area has a massive jump in comparison to the main spark tables.

that bigger jump... ball park 15 into the main table at 36-41 will cause a violent jerk

[SydneyACE]

your idle spark table in the 1600-2400 rpm area has a massive jump in comparison to the main spark tables.

that bigger jump... ball park 15 into the main table at 36-41 will cause a violent jerk

This is spot-on!
I was having the same issue. I just copied my Main Spark Advance table and pasted it into the Idle Spark Advance table, and it alleviated my jerking/bucking issue SIGNIFICANTLY!
It will still buck once or twice transitioning from off to on throttle, but they are minor (comparable to stock) and it dissipates quickly (whereas before it would get worse and worse until I pushed the clutch in).

I had no idea that it was using the "Idle" Spark Advance in that RPM range, but apparently it was. (Which explains why that table covers up to like 4,800RPM.) Not sure who considers that "Idling" but...