Honda Fit Jumping while idling

My Honda Fit has had this problem for over a year; I’ve brought it in to multiple shops and they couldn’t replicate it. I first thought it only was happening when the a/c was on, but now that it’s winter, and the heat is on, it seems to be occurring all the time. The car will “jump” (bump?) when idling, and will now (newly) do the same thing wile driving. Has anyone had this problem? I can’t identify what it might be and when I bring it to the shop, it decides not to do it when they test drive.

What year is your car? How many miles does it have? Is all maintenance up to date? Has the check-engine light ever come on?

Has anyone checked the idle air control? Now that it’s happening while you drive, maybe this isn’t it, but it’s worth checking anyway if you ask me.

Is it the on/off cycling of the air conditioner compressor causing a variance in engine RPM? In most cars the AC is on whenever the climate controls are set to have the defroster on. You may feel it as a slight “bump” or jerk, as if a spark plug misfired, when the AC compressor engages or disengages from its drive belt.

You can turn off ac and see if it happens. Also, defrost turns on the ac automatically whether it’s selected or not. The iac changes idle speed when your foot is off the gas. It can be cleaned. I would clean in and run a large bottle of Techron through a tank of gas. Check under the hood at night and look fur sparks around the coils.

Is it a “bump” like someone tapped you on the rear bumper, or a step change in engine speed?

Does the tachometer jump when you feel it happen? Has the throttle position sensor (TPS) been checked?