lopping engine cold start after 4-5min idleing

[wicsmith1997]

A few mornings now I've had this issue.

1997 XLT 4x4 4.0 OHV 225K miles (Only owned since 220K)

Any Idea's where I should look to correct this issue?

1) Cold morning < 32
2) Vehicle starts up fine and idles fine for the first 4-5 minutes then it starts lopping(Only term I can think to describe it).
3) Some white steam out the exhaust but no Anti-freeze smell.
4) RPM's just under 1000 so 900 I'm guessing (RPM's aren't bouncing either its constant at 900).
5) Temp gauge has not yet moved at this point.
6) When backing up initially it wants to choke down.
7) Stopped at bus stop with son and continued idling again. Temp gauge now moving up and vehicle shuts off on its on.
8) Starts back up and runs fine again Lopping does not return.
10) Drive to work 10+ miles away and sit and let it idle for over 4-5min and lopping doesn't develop.

Known issues:
1) EGR codes. (forget which ones but needs new sensor)
2) Was and maybe still is loosing anti-freeze. Was loosing antifreeze and tightened some hose clamps that was leaking this weekend to soon to know if I'm still loosing any

Fuel Filter, Plugs and wires replaced less then 1k miles ago (auto-lite wires, motor-craft plugs), Thermostat was replaced at this time as well

 

[wicsmith1997]

Bumping it for the evening crew.

 

[BradR]

Can you define "lopping" with other words?

 

[swetrid]

Could be intake gaskets?

 

[wicsmith1997]

I guess it sounds like the engine is idling fine then chokes down then idles fine then chokes down again in rhythmic pattern. However rpm's stays constant. Same pattern applies to the sound from the exhaust as well.

 

[wicsmith1997]

I was thinking maybe air intake sensor of some sort? Mass Air Flow sensor, or Temperature of incoming air sensor or something along those lines as a maybe?