I know this is kind of an odd question, but I started thinking about the fact I have read on this site the factory PCV valves are better than aftermarket because they flow the proper amount.

It got me to thinking about the vented gas cap. Is it possible an aftermarket gas cap could cause running problems? Mainly because it doesn't vent properly.

I am curious to see if anybody on here has ever concluded the gas cap was the cause of their problems.

I might be way off base here, but I figured it was worth asking about.

 

i don't think so.
all gas caps have a one-way check valve built in. its to let air in (to replace the gas you use) and not let fumes out.

a check valve that won't hold pressure inside (fumes in) will turn on a CEL. that's determined by the evap system pressure tester.

a check valve that did not exist or work might create a temporary low pressure situation inside the tank, but when the evap system cycles, i think it was balance out.