(SOLVED) - - - Idle gains 500 (unwanted) RPM's

[Cheddar_Dan]

Hi All,
I don't notice a RPM issue in the (cool) mornings, but warm-up engine gains 500 in the heat of the day. Hmm?
Ideas welcome!
Best!
.cd

1994 4x4 auto XLT 4.0L

 

[Roadrunner777]

I had that with a failed MAF.

 

[Cheddar_Dan]

BIG Thanks!

 

[Cheddar_Dan]

ISSUE: Low coolant level caused heated engine idle to increase.
FIX: Add coolant to correct condition.
Thanks!
.cd

 

[92exp4x4]

Love it, when it's simple!