Whenever I cold start my truck, warm or cold temps, it at first hangs around 300 - 400 rpms for a few seconds, like if hanging between running or not. After that few seconds it either dies or fires up to the above 1k rpms like it should. If it dies, it usually fires right when I try to crank it the second time. Might be a little sluggish and bad mpg. Changed out my 02 sensors, cleaned MAF, etc. I checked the EGR valve and the pipe and pulled apart the throttle body and nothing was plugged, they are all completely clean inside. I’m guessing it’s a possible sensor issue, but how do I diagnose those, and what sensors are they and what do they look like? Thanks.

 

What year and size engine?

 

2001 4.0l