Chrysler Repair: Dual Vacuum Solenoid 88 Chrysler, power brake booster, vacuum line

Question
Hi Roland, I own a 1988 Chrysler Fifth Avenue (I realize that it is a rear-wheel drive vehicle, but I think you have the knowledge to help me, based on reading some of the advice you've given others).  I experience intermittent surging and sputtering during part-throttle, especially when driving uphill.  The "dual vacuum solenoid" is making noise, which leads me to believe that it is the source of the problem.  (I'm sure you know, but it is located on the firewall behind the air filter).  I recently discovered something very peculiar about the surging and sputtering: if I turn on the heat or defrost, the car gets an immediate power boost and the surging/sputtering immediately dissipates.  In this regard, I swear I can hear a very faint hiss when driving w/out the heater/defrost running.

Could you please tell me what you make of these symptoms?  

Also, is the "dual vacuum solenoid" (what the folks at Chrysler call it) the same thing as a "mixture control solenoid"?

Thanks so much for your help!

Josh

Answer
Hi Josh,
Flattery will get you somewhere, but in this case I am really at a loss for detailed knowledge because the '83 RWD manual is all I have. I don't even know which engine and fuel system you would have and how it would relate to the '91 FI models which is on the other side of the time frame that I have manuals for the V-6's. But I do note one very relevant observation, the role of the heat/defrost and the hiss in this problem. The AC/heater air mode doors in that time frame were operated via a vacuum line off the intake manifold. The line usually branched off the main vacuum hose that goes to the power brake booster and it is very fine in diameter and therefor subject to breaking or disconnection from its fittings. It would be routed thru the firewall roughly at the midline of the body. So I would examine that line on both sides of the firewall (though it will be a bit trickier on the cabin side) for leaks due to cracks or frank breaks. There is also a check valve in the line that temporarily holds the vacuum in the door side of tje system when you step on the gas and drop the vacuum level which would cause the air distribution to otherwise vary with the pedal situation. I bet you are hearing a vacuum leak that is effecting the mixture either directly or through the solenoid you described.
Roland