Car Bucks at Low Speed with Clutch Fully Engaged

[Bcoaktree]

Can someone help me out with the following issue?

When I'm driving in first or second gear, the throttle and transmission don't seem to work together smoothly. The clutch is fully released, but if I tap the throttle, the car jerks and bucks like I'm riding a wild horse. It's especially noticeable at low speeds or when I'm trying to feather the throttle lightly. It also happens when shifting into first or second gear but can be replicated by cruising at low speeds. Two ways to stop the action, pull completely off the throttle or commit to a generous dose of the throttle. If you shift above 3,500 it doesn't require as soft of a left foot.

Any thoughts on what might be causing this? I don't know if this is the known 1st-2nd gear issue? Sorry for the music, I decided at the last minute to shoot this video and ask for help.

https://youtube.com/shorts/1Onvkgan9oQ?feature=share

Edit: I’ve removed the clutch delay valve (CDV) and switched to Redline fluid. Next week, I’ll change to Royal Purple Synchromax and replace the transmission mounts with poly flex bushings. A few thousand miles ago, the engine mounts were replaced.
On a whim, I’ll run a bottle of BG 44K through the fuel system in case of injector or throttle issues, though I doubt it’s necessary and a waste of money but...I'm grasping why its so touchy. You can't even sniff the sport button as its almost impossible to shift from 1st to 2nd gear without going for a ride.

 

[RedUn]

Looks like MAF to me based on the video, give it a clean with some contact cleaner.

Might be worth sticking a new one in

 

[Bcoaktree]

I ordered a can based on your input. Tonight, while I was out in the garage getting ready to disassemble and clean, something caught my eye — the brake fluid reservoir is empty; I can't see any fluid. I realized that when I removed the CDV, I forgot to refill it. I'm wondering if that could be the cause. Maybe...? I ordered some brake fluid and will give that a try too. Hopefully, it's that simple.

 

[RedUn]

Keep us posted on how you get on

Not great on the brake fluid but at least you've found it, how low is low? You might have air in the system now?

 

[Bcoaktree]

Well, the fluid level was fine—I added maybe three tablespoons. The discoloration of the plastic made it look low, and I was kind of hoping that was the issue.

What I did just find (I don’t drive the car much): the connection on the elbow behind the MAF sensor—the air shut-off valve line—was disconnected. Based on what you said about the MAF, I have a feeling we found the problem. I'm not sure when we disassembled it, but clearly we didn’t reconnect it.

Getting old sucks... I wouldn’t have made that mistake 10 years ago.

GPT says. A malfunctioning air shut-off valve line on an S54 engine can lead to various issues, including rough idling, low power, and potentially even engine stalling. The air shut-off valve, also known as the DISA (Discontinuous Intake System Air) valve, plays a crucial role in regulating airflow into the engine, particularly at low to mid-range RPMs. When this valve or its associated lines fail, it can disrupt the airflow, leading to the aforementioned problems.

 

[mmm-five]

GPT says. A malfunctioning air shut-off valve line on an S54 engine can lead to various issues, including rough idling, low power, and potentially even engine stalling. The air shut-off valve, also known as the DISA (Discontinuous Intake System Air) valve, plays a crucial role in regulating airflow into the engine, particularly at low to mid-range RPMs. When this valve or its associated lines fail, it can disrupt the airflow, leading to the aforementioned problems.

Another AI hallucination, as the S54 doesn’t have a DISA valve, but those shut-off lines will simply go directly to the intake manifold

 

[RedUn]

Well, the fluid level was fine—I added maybe three tablespoons. The discoloration of the plastic made it look low, and I was kind of hoping that was the issue.

What I did just find (I don’t drive the car much): the connection on the elbow behind the MAF sensor—the air shut-off valve line—was disconnected. Based on what you said about the MAF, I have a feeling we found the problem. I'm not sure when we disassembled it, but clearly we didn’t reconnect it.

Getting old sucks... I wouldn’t have made that mistake 10 years ago.

GPT says. A malfunctioning air shut-off valve line on an S54 engine can lead to various issues, including rough idling, low power, and potentially even engine stalling. The air shut-off valve, also known as the DISA (Discontinuous Intake System Air) valve, plays a crucial role in regulating airflow into the engine, particularly at low to mid-range RPMs. When this valve or its associated lines fail, it can disrupt the airflow, leading to the aforementioned problems.

That'll do it

All good now?