engine stalls when oil cap is removed

[L.D. 100]

does anyone know where I should look? Ive already took the head to the machine shop and got everything checked out, supposiveley theres nothing wrong with it and it should be good to go. were else should I look?
thanks in advance

this is a ka24e btw

[anthony240]

why would you want your oil cap off while the engine is running? that would just spew oil all over the engine.

[johngriff]

this is one i havent seen before. My proposed theory is that you're vacum system has somehow become connected to you're crankcase recuirc system, when you open the cap, vacum dump to pos 0 (14.7 atmospheric!) and stall the bitch out.

Proposed diagnostic:

Hook up a vacum gauge, then slowly take the cap off w/o stalling the engine.. does the vacum change? what is the reading?

If the vacum does start getting weird when doing this (taking into account the stall of the engine), you may want to "recheck" you're vacum settup per the oem diagram..

[SpeedMonkeyInc]

Well what happens when you take you intake arm off? Same thing right? Thats because the engine is taking in lots of un-metered air. When you take off the oil cap you open an air source straight through the IACV from the valve cover crank case breather. Kinda the same as taking off the air intake pipe. I don't know WHY it happens, but that is my best guess as to what causes the engine to die when you remove the oil cap.

[xkamikazestormx]

i think it should be fine.

after i did an oil change, i forgot to put the oil cap back on, and started the motor. even though it didnt stall, the rpm kept on fluctuating ... so i popped my hood, close the oil cap, and fixed.
p.s. i didnt drive it. it was just idling

[NemeGuero]

Yah, don't take it off. Why would you drive with it off?