Why do RPMs jump while holding a steady accelerator?
When holding steady pressure on the accelerator, engine RPMs can jump repeatedly while the car's power goes in and out. This surging occurs during acceleration even after completing gearbox adaptations and fluid top-offs, and it may be accompanied by crankshaft position signal failure codes.
What the numbers show
Counted from the threads quoted below. How we count
- People have been saying this in most months since September 2026.
- This comes up 11.0× more often in r/MechanicAdvice than across the site as a whole.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
Why do RPMs jump while holding a steady accelerator?
- 1doing gearbox adaptationDid this help you?
- 2topping up gearbox oilDid this help you?
- 3Check transmission fluid levelDid this help you?
- 4Inspect the air and fuel mixtureDid this help you?
- 5Seeking diagnostic help on online mechanic forumsDid this help you?
- 6Investigating the transmission torque converter clutch or solenoidDid this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“This is volvo s60 2014 2.5 petrol with tf80 sc gearbox. On autopilot it drives smoothly, this happens only when accelerating. Thanksss. Adaptation has been done successfully, didnt change the problem. Gearbox oil topped up properly. Only fault codes that I can see are with crankshaft position signal failures, no idea if that could even be related”source ↗
“When driving and steady pressure on the accelerator the rpm’s will start jumping around repeatedly and you can feel the power kinda go in and out.”source ↗
“But I noticed today while driving at around 165 mph. It's doing very slight subtle jumps in my RPMs are jumping very very slightly.”source ↗
Where this came up
People with this problem also raised
- 7Why does my car lurch and shake when I accelerate at low RPMs?
- 2Why does my steering get sharper when I accelerate?
- 3Charging system voltage drops when revving engine
- 9Why does my car jerk and whine when accelerating around a turn?
- 4Why does my car vibrate only when accelerating?
- 2Why won't my car go past 4k RPM when flooring it?