Engine Surge

Truck has a surging or pulsing going on while idling and in park. Rpms aren’t changing or fluctuating. Ideas?

 

Check engine light? Recent maintenance? Miles? Engine?

 

Check the IAC (idle air control) valve. Those are common symptoms when it goes bad.

Edit: i think the rpms would fluctuate though...maybe not

 

No check engine light. 203000 miles. Throttle body does need to be bored. Has a small gap around flap.

 

If rpms aren't fluctuating much, your AFRs may be swinging indicating a bad AFR sensor. Does it surge when you first start it, or after it warms up?

 

It's pretty rough and consistent when first started. It will do it a little bit while warm (gentle) and a little more when a/c is on.