My 2007 Fit (~130k) had a check engine light come on a couple of days ago and started to get the stutter that so many other people report, making me think it was time for new coil packs and/or plugs. However.......

Today, when I turned on the car, the check engine light was off and now I have crazy lurching RPMs. Whether its idling, in gear, or out of gear (clutch in or out), the RPMs go down and up significantly (at least 500) like clockwork. It is perfectly regular, and about once every 1.5 seconds. I took out on the highway to check different speeds and it is exactly the same behavior there too. It's like somebody is taking their foot off the gas, then putting it back on every second or 1.5 seconds.

Could this be related to the probably coil pack problem? Or is it something worse? Any ideas?

 

Check engine light set a code. Please retrieve it and post it here.
Using the code reader is the best way; this method may work as well but not easy for inexperienced user https://www.fitfreak.net/forums/fit-...ode-check.html
Intermittent short in coil can cause idle surging as well as out of calibration TP sensor or HUGE vacuum leak (small leak is unnoticed thanks to MAP sensor)

 

I and a paperclip got these two:

41 – Primary oxygen sensor heater
and
48 – LAF - lean air fuel sensor

I also got a video of the RPM fluctuation if that is helpful:

 

Might be a coincidence (similar things have happened to me), But your RPM vid seems to be similar to that caused by a dirty throttle body.


I'd clean it, then do the Idle Learn Procedure.

Of course, a lean condition can cause the same surging....

report back on any results.

 

Thanks for posting the codes and using old school but reliable method!!
Air fuel ratio sensor (in the exhaust manifold) has no voltage going to the heater; surging caused by shifting from rich to lean.
Please check 4-wire sensor connector; be sure that no wires are pulled from it and connector is clean and dry.
If so check, unplug the sensor and check resistance of the heater (2 BLACK) if open or shorted, replace the sensor
if resistance is in typical (5 to 15 ohms) check that the mating wires have 12 volts with ignition on, engine off.
If no voltage there is break in the wire from ECU and sensor connector.