1. Takes about 10 secs to crank then hi idle
2. Once warm it runs fine and cranks up immediately
3. after ~50 miles of driving Check Engine light on
4. once stopped at red light, miss idle but not overly rough idle...

Question: Would a badd O2 sensor be a possible suspect? Its never been replaced.


5.7L TBI
215K miles

 

it could. i suspect bad/dirty idle air control valve as well, possibly dirty egr. timing could be off. vacuum leak(s) how long since cap/rotor/plugs/wires/filters been changed?

 

It has been ~1.5 years but < 2000 miles ago on filter, plugs, wires and cap/rotor. Never have replaced EGR or IAC valve either.