Hi, I have a 2001 3.0L V6 ranger and recently it started running rough at idle and low rpms. After a few seconds it jumps back up to normal revs and runs great. These are the new parts I have put in:
Spark plugs, pcv valve, all o2 sensors, and MAF sensor. None of those helped. Could it be a vacuum leak, and is there a way to test for a leak with the engine running?

 

start motor and let it warm up. ck gauge unplug the IAC. the motor should barely run or stall. if the idle doent change or stays high most likely you have a vacuum leak.