Engine Stuttering when maintaining speed

I have a 2005 Honda Odyssey with 144k miles that is stuttering (vibration in the steering wheel and accelerator) when maintaining speed between 35-50mph. It doesn’t stutter if I’m going uphill while trying to maintain speed.
I just changed the spark plugs because I thought that might be a potential cause. I have plenty of power to accelerate, and it changes gears with no noticeable issues.
Any guidance would be much appreciated.

You might check up inside the coil boot with a decent light and try to determine if there is ANY corrosion at all in there. I’ve seen instances of similar complaints caused by something like this.
Runs fine at idle, under acceleration, etc but will stutter at certain maintained speeds.

Does this feel like you’re driving on the rumble strips on the shoulder of the highway? If so, a failing torque converter is a common source of this issue on Honda and Acura cars from those years.

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+1
It could be a problem with the torque converter itself, or–more likely–a problem with the torque converter lock-up mechanism.

Many people misinterpret this transmission problem as an engine problem.
:thinking:

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Do you have any fault codes? If so, what are they?

Shift it manually and determine if it is truly speed dependent and not engine RPM dependent.

My guess is a torque converter lock-up problem too. On some vehicles it is possible to temporarily disconnect the torque converter solenoid so it doesn’t even try to go into lock-up mode.

Thanks everyone. I’m going to look into the torque converter as a possible solution. I didn’t see any corrosion on the coil boot.

Originally I did have a fault code for one (or more?) misfires, which is why I mentioned that the spark plugs were replaced. That code was cleared and hasn’t reappeared since replacing the spark plugs. The only other code is for the O2 sensors with the catalytic converter. I’ve been advised that’s not an urgent fix.

A plugged up cat could cause this symptom. Not saying it is the cause of your problem, in fact I’d guess it wasn’t based on your symptom description. But keep that as a backup. The engine won’t run well, will misfire, stumble, etc if it can’t freely expel the exhaust gasses, b/c if they can’t get out they prevent the new air and gasoline from coming into the engine. A plugged cat would show up worst during heavy acceleration, going up steep hills, and high speed driving, conditions where the maximum air flow into and out of the engine is required… It’s fairly simple job to check for a shop to check for a plugged cat on most vehicles.