Hey guys, I have an 02 Ranger 135k miles on the 4.0. I'll get straight to the point, I have a horrible idle. It is fine until it warms up....then it starts going "vroom vroom vroom vroom" then if you dont feather the throttle it just dies. I also have two codes, one for each bank running lean.

I've replaced the IAC valve, MAF sensor, 02 sensors, spark plugs and tried some seafoam in the manifold. I'm thinking next I'll look at fuel injectors, but I'm running out of ideas. Any input is appreciated! Thank you!

 

If it runs fine at cruise or higher rpm's you are looking for a vacuum leak.

 

That's exactly what I was thinking.

 

Running lean would indicate that there is unaccounted air in the system causing ratio to skew. I X3 the vacuum lean. Ckeck all tubes going to plenum, intake tube past MAF, and plugs to make sure all are tight.

 

PROBLEM SOLVED! Took a while to find it, but right under the upper radiator hose where it goes into the manifold...there is a little pvc elbow, it had a huge leak in it! Now to find a replacement! Thanks guys!

 

I hear that is common on the SOHC's, I don't have one though.