Dodge ram cold start/ run problem

My 98 Ram 1500,V6, starts up fine,but after about a minute it bucks,backfires into the intake,does not take gas. Except full throttle. After it warms up, it runs fine.It does it in cold and warm weather. I put a new coolant sensor in and it ran fine for a week or two,now the same problem again

Check the connector at the CTS.

connector seems fine. I should mention that there is no trouble code stored.

Check for vacuum leaks.

Here is something else to look at: With the engine off, remove the air snorkel on the throttle body, open the throttle completely, and look down into the intake manifold with a flashlight. The bottom of the intake manifold should be fairly clean. If the bottom is coated in oily sludge, the intake manifold belly pan gasket is leaking.