[Bowtiemiami]

I just changed the head gaskets on the car after building it back up had idle issue after about 20 mins of car running. Idle jumps up and down between 500 to 1300 rpm. i found a couple vacuum leaks repaired those and it still idles rough after warming up and even rpm jumps while driving. checked fuel pressure it is at 40 pounds koeo and goes to about 37 with engine on. i pulled vacuum at regulator and pressure jumps to 47 but no fuel is leaking out of vacuum port could this be my problem?
I pulled the maf sensor no change. i am going crazy already lol
any help would be appreciated
thanks

 

[Starship]

Welcome to the forum. The fuel pressure values sound about right. The fuel pressure regulator is doing its job as well.

Head gaskets mean the lower intake manifold gasket as well. It makes me wonder about "a couple vacuum leaks" which may indicate a botched job. There's probably an air leak somewhere still. The amount of the air leaked would largely depend on the manifold vacuum and thus relatively constant. It then represents a larger percentage of the total at lower RPMs (low air volume, high vacuum) and thus will have a greater effect on idle.

 

[Bowtiemiami]

Thanks for the fast reply I did the job myself and replaced all the gaskets the leak I found was a couple cracks at the upper intake manifold. What should vacuuum preesure be at idle? Also I took the car out for a drive and no problems till I put it back in park. I had cleaned the maf and isc that seemed to help.
Thanks in advance

 

[Starship]

There's no reliable way to glue/seal cracks around the bolt holes and thus I hope that's not the case. The vacuum at the LIM should be 15-22 in-hg. It's really not a good indicator since air leak large enough to register on the vacuum gauge will stall the engine. I'd check the intake manifold and maybe the PCV and EVAP plumbing.

 

[DrivenDaily]

I keep seeing this LIM acronym. What does it stand for? Less Is More?

 

[Bowtiemiami]

Ok I'll check it out tommorrow I'll let you know what I find
thanks

 

[RalphP]

I keep seeing this LIM acronym. What does it stand for? Less Is More?

Lower Intake Manifold.

As opposed to the UIM - Upper Intake Manifold.

RwP