Engine Rumble while accelerating to maintain speed

When this first started the check engine light came on and the engine rumbled horribly while accelerating, this was probably around 50-60mph. Occasionally the rumbling would stop, check engine light would blink, RPMs would drop by about 1k. After a few moments the rumbling would start again and the check engine light would go back to solid.
About an hour later the check engine light turned off and the engine rumble had ceased. Another 30 or so minutes and the rumble would come back while giving just enough gas to maintain speed. Accelerating enough to get to around 2.5k RPMs would stop the rumbling. All of this happened without a check engine light.
Since then the check engine light blinked on briefly with no changes.
All of this happened yesterday. Oil levels are on the lower end of normal. Transmission Fluid is a bit over-full.

Update: Rumble has stopped and Check Engine light is off. Plugged in an OBD Scanner and it came up with nothing. I'm guessing because the check engine light shut off. I don't trust that this won't happen again in the near future.

 

Have you checked for loose connections? Your air hoses and vacuum lines should be checked for leaks.

 

almost Always helps to know engine type (trans ) + mileage

no codes not enuf to go on

' rumbling / knocking ' are 2 different sounds from different locations

either could be catastrophic

1 guess sounds like U might be down a cylinder