Stalling with oil cap off??

[Matt_vp]

A family member has a rb30det out of a vl in an eh holden. The first motor he had in there had a blown head gasket from when he brought it, so he pulled an rb30 out of a r31 skyline he had sitting in the paddock. After putting the motor in he started it and it is running really ruff and the idle seems to be hunting, When you unscrew the oil cap the idle goes down and it stalls after a few seconds. When the motor was in the skyline he opened the oil cap when it was going and it didn't stall and the idle was unchanged.
Any ideas, he is about to cover it with a tarp and give up.
Matt

[kane88]

Um, try to resist the urge to unscrew the oil cap while driving?

[shiftySLE]

Hunting would ususlly be vacuum or something, are all hoses connected, is the hunting regular or is it more of a missing.

[kane88]

On a more serious note, I'm going to go out on a limb and say the AFM was damaged during the transplant, they s**t themselves pretty regularly...

[Not_An_Abba_Fan]

And make sure the AFM has a good seal on both sides as well.

[Matt_vp]

Yeah we thought the afm he is going to try a diffent on now or test the old one. As for taking the oil cap off, im sure i didn't say while driving, but i thought that might have something to do with the problem so i mentioned it because i have never hear of it happening, but i dont play with jap motors much. It doesn't seem to be missing just hunting. We checked all the vacume hoses and cant find any leaks.
Matt

[Goon]

wouldnt taken the oil cap off drop all compression and stall anywayz?

if u took the air intake off while the transplant id say its somethingto do with that too..

[Matt_vp]

I didn't think that compression would be in the tappet cover.
Matt

[Matt_vp]

OK problem solved, it ended up being the maf and iac valve.
Thanks for everyones input.
Matt