While on a trip with my '91 f53 I developed a high running engine. I discovered a vacuum leak. Between the venturi in the fresh air intake and the manifold below the throtle body there is a 3/4 inch hose with a plastic cylinder that looks like a check valve on a brake booster. I took it off and it was hollow like it lost its guts allowing air into the manifold. Ford says it is an obsolete part, and the parts people don't know what it is. I took a wine cork and insterted it in the hose and drilled a hole in it to allow air to give me a idleing rpm. Question - what is it ? Where can I get one ? I have no cold start high idle without it.

 

Do you have a picture? I don't know what engine you have and I don't know what "f53" is... F350?

 

Post up a pic and/or tell us what truck and motor its on.