Chrysler Repair: 82 Mitsubishi 2.6L: popping noise in air cleaner

Question
QUESTION: Hi Roland-

I have a 1982 Chrysler Lebaron with the Mitsubishi 2.6 engine.

I noticed a popping noise from under the hood and it sounded like an exhaust leak. Upon further investigation the noise is coming from inside the air cleaner. There is a tube that runs up through the center of the filter and a pop-pop-pop noise comes from this. If I stick my finger in the tube I can fell pressure and it quiets down. The hose that connects to this tube runs around the side of the engine and goes under the carburetor in the front of the engine. An acquaintance has a 1984 Lebaron with a 2.6 and his engine bay looks like mine but his air cleaner tube makes no noise. My mechanic looked it over and said he has no clue what that tube does or how to fix it. Other than 2 vapor lock(?)issues this summer -- extended driving with the A/C on-- the car runs/drives fine other than the popping noise. Any ideas?

Thanks,
Jim

ANSWER: Hi Jim,
My closest manual is an '83 and it shows that there is an emission reduction system called a heated air inlet system which allows either ambient air or heated air or a mixture of the two depending upon the ambient temperature to be provided to the carburetor. I am not certain that the 2.6 engine system in '83 is identical to what you have on your '82 because I don't have a picture of your engine to compare to the drawing. The system does involve some vacuum hoses and those can of course get hardened and then either crack or come loose from their fittings.
There is also a temp sensor and a vacuum motor and a bi-metal temp valve. So I would begin by looking over the entire air intake system and locate any vacuum lines related to that system to find a cracked or disconnected hose. The manual then describes further tests related to the temperature of the air in the air cleaner/carb in-take area.
Probably the best I can offer is to photocopy the pages from the '83 manual and postal mail those two you early in the week. If you would tell me your postal mailing address I will do that at no charge.
Please read the PS below and respond to it.
Thanks for doing that,
Roland

---------- FOLLOW-UP ----------

QUESTION: Hi Roland-

Thanks for the quick reply.

I think I know what part you are talking about, it is connected to the inlet snorkel of the air cleaner with a pipe that goes back to the exhaust and a vacuum line that attaches to a flapper inside the air cleaner inlet, maybe 2" in diameter.

My noise is coming from inside the air cleaner, from a pipe that comes up through the middle, about the diameter of my thumb. It goes from the base of the air cleaner housing (which is on the back side of the engine by the exhaust manifold) around the side of the engine by the water pump and then under/into the carburetor/intake manifold. The tubing switches between rubber and metal but stays about the same size.

Sometime in the next week or so I could try to take some pictures of my engine bay and the tube I am talking about if this would help. Also I listened to it again and it is more of a pfft, pfft, pfft noise, like an exhaust gasket leaking, instead of a sharp popping noise.

Thanks,
Jim

Answer
Hi Jim,
I found another emission control device which I believe is the problem: the Aspirator Air Valve (or possibly the rubber pipe from the valve to the air cleaner). You probably saw it but didn't recognize it.  It is said to cause excessive noise under the hood at idle and low speed when rubber hardening happens. The system connects by a metal tube to the exhaust manifold, that tube goes to the aspirator valve and then to the air cleaner with a rubber hose. Check all those connections and the rubber tube for leaks and for hardening/cracks. Chances are though that the aspirator valve itself, which has a rubber diaphragm washer internally, has failed and needs to be replaced according to the manual. It is threaded onto the manifold tube on one side and has the rubber hose connection on the other side. So look along the tube you described, where it changes from rubber to metal, and that is the 'connector' which constitutes the valve itself.
Please let me know if this is correct.
I would very much appreciate your rating my answers and offering me a nomination for 'volunteer of the month' which you can actually twice (once for each answer) and both will be "counted".
Roland