Starting issue

[jbellingham]

Can I ask what you mean about open loop/ closed loop transitioning??

 

I recently changed the 02 sensor, so I assume that’s ok.  It was doing the same thing with the old sensor.   Basically, when the engine is cold it will idle nicely for about 15 seconds, then  RPM will drop and the engine sounds like it’s labouring for 5 seconds or so, then RPMs increase for another 10-15 seconds, and it repeats over and over.  Once the engine warms up, the idle usually straightens out.     I assumed that this was abnormal, as I have a Jeep TJ with 4.0 that never acts that way when idling. 

 

ive done the following to try to resolve:

- new idle control valve

- new 02 sensor,

- tps test and adjustment 

- ground refresh

- swapped throttle body and vacuum line going to MAP