Uneven Idle When Cold

[mowfixer]

My 99 Sport 4.0L OHV seems to have uneven idel when I first start it. The idle fluctuates 100 or 200 RPMs slowly, fast idle looks like somewhere around 1200 rpms. After it is running for a minute or so it is fine and idle is nice and stable.

Any ideas on what the cause might be?

 

[ExploringNC]

Sounds like a manifold gasket leak. Not sure on OHV but on the SOHC the maifold gaskets have a tendency to leak and will act that way.