I purchased a 2006 Honda Accord with the 3.0L V6 V-Tech engine about 18 months ago. It currently has 141,000 miles on it and all service is up to date as far as I know. I have noticed the rpm gauge fluctuates but only at a very specific point. When the transmission is in 5th gear and the rpms are about 1500 and I am traveling at about 45mph the rpm needle will bounce about 50 rpm's every 5 seconds. The car is up to temperature when it does this but it will stop after about a half hour of running. I live in Minnesota and it has been very cold here. I never noticed this when it was warm out but I wasn't looking for it either. Has anyone else had a problem like this? Could it be an ignition coil problem? I had read a few posts that were similar but had a very large rpm fluctuation and the replies had indicated an ignition coil issue.

 

From your description, suspect the lockup torque converter is locking/unlocking. This will cause an rpm swing of 50-150 rpm depending on engine load.

Do you have a Check Engine Light? An electrical fault in the lockup solenoid circuit would set a code.

If not, it may worth asking Honda to see if there are any TSB's that might address your problem.

good luck