Hey I’m new to this hopefully I get it rite I’ve got a 94 5.2l zj that won’t start when it’s cold unless throttle is applied for a minute or two depending on temperature, once it running idle is fine until it’s driven and returned to park then the rpms fluctuate from 800-1100, I can shut it off restart and rpms stay at around 900 I have cleaned the throttle body and replaced iac,tps,and the map sensor also took starting fluid to try to find a vacuum leak with no success not sure where to go from here any suggestions would be greatly appreciated

 

IDK for sure, but I've been told there is a plenum gasket on the bottom of the intake manifold that likes to rust out and leak. It's a thin metal plate that closes off bottom if the casting. It's hard to diagnose without removing the manifold. That's all I've got.

 

I was told it would be using oil if it was that gasket so I haven’t dug into that yet

 

Since I've never had a 5.2 apart, that was my best guess.

 

Welcome to the forum.

This reply shows the reasonably thick aluminum plenum pan. Some elect to upgrade to a thicker part, but not because this part rusted out.

Yes, a failed plenum gasket permits manifold vacuum to suck / burn engine oil.

The steps you've followed are reasonable. I would connect my DRB II tool to verify the misbehaving engine has control of IAC and permits setting the idle to manually selected higher rpm levels.

The symptoms indicate to me a vacuum leak or no IAC function.