I have a 2010 2.3 Ranger 110k miles. I just replaced plugs, and purge solenoid. Purge was stuck open, throwing rich running code. Much better now especially after cleaning out IAC and throttle body and MAF. Haven't driven it much, so code hasn't come back yet, but a quick test drive around the block, the spark advance at park in drive way fluctuates between 15 - 20 and RPMs are fluctuating between 850 - 870 in park. There is just a little shake every so 3 seconds, but seems to be mostly smooth at idle. Fuel filter was also replaced a day ago. It seems like it could, should be running a bit smoother though.

​​​​​​Should RPMs and spark advance be steady or are these fluctuations normal?

Thank you.

 

Idle RPMs should be steady, computer/IAC Valve should be +/-4rpm once fully warmed up, during warm up idle will vary based on CHT(cylinder head temp) sensor

Spark advance can vary when idling because computer must add extra fuel now and then to keep Cats HOT, or if engine is not fully warmed up yet

 

Thank you RonD. I will explore those items further. IAC was dirty, and cleaned it out pretty good. I may just replace it along with the CHT and see if that improves it.