Possible Vacuum Leak?

The electrical portion breaks and causes electrical gremlins. The part is $8 and with a small screwdriver and some contortion it can be replaced in a jiffy.

That said, did you reset the computer after replacing the spark plug? The engine may have tried to compensate for a bad spark plug. I would disconnect the battery and reconnect it after waiting for 30 seconds. But first make sure you have your radio code. After reconnecting the battery the engine may run rough for a short while while it relearns the mixture adaptation settings.

Thanks for your interest,
It's not the ignition switch, it was replaced less than a month ago and this problem has been with the car since I first purchased it. What I wanted from this post was info on vacuum leaks and whether there is a vacuum sensing device in the vacuum circuit.
Would love to hear from someone that has actually been there.
Thanks again.

I would start by cleaning the idle control valve. Over time they tend to stick, which causes the engine to have to hunt for the right idle speed. With a torx screwdriver and a solvent it is quite easy to DIY.

Thanks Boxsterra...Good info to know...I will check it out and report..
Thanks again.

... if it's a '97 - '99 I'd heed Boxsterra's advise and clean the idle control valve.
If its a 2000 or newer, the clean out the throttle body, since the idle is controlled by the ECU through the TB's butterfly valve.
Keep in mind that the A/C automatically cuts out the compressor when you accelerate.
The heater is always on, meaning that coolant is always circulating through the heater core.
Air flaps control the flow of the air over the heater core or the evaporator.
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

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"If you wait, all that happens is that you get older"... Mario Andretti

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Hi Pedro, congrats on a very good board. I am enjoying it.
1997 Boxster, 140,000 miles, non turbo. Replaced/Repaired so far, Ign switch, both window cables ,Autolite Platinum plugs AP3923 ,Oil & Filter, Front motor Mount.
Yes I will follow Boxsterra's advice, his thoughts on the Idle problem sounds solid....I will report via this mediuim.
Thanks for your thoughts on the heat/air condition...I loose both a/c compressor and blower motor when it acts up. While it's acting up, I can hear the flaps inside the heater/air box move when I change controls, and the lighted panel indicator lines for the blower change with auto and manual settings, so I must have 12 volts to the control panel, but the motor fails to run. The blower motor is good, and the connector to it is clean. I installed a temporary relay and switch to the blower motor to make the car useful till I can fix it properly.
Thanks again for your thoughts and time.

Howard Goodwin
Eastern North Carolina.

1) If you have any kind of substantial vacum leak, the engine management would kick in fairly quickly. You would get unmetered air in the combustion chamber which would trigger something pretty quickly. You can probably check for that in another way by looking at real time numbers on a code reader. Look at the long term and short term fuel trims and report your findings here. Those numbers will tell you quite a bit.

2) If you DO have a vacum leak, the easy (and very old school) way to find it is to take the car OUTSIDE on a calm day. Get a propane torch and just crack it open, such that the gas is barely running. With the car running, drag the unlit torch end over the vacum hoses and fittings. If there is a leak, the propane gas will be sucked into the engine and the rpms will increase. It will be a repeatable test too. You MUST be outside so the gas can disipate safely. If you smell the gas getting concentrated, walk away, close the tank and let the area ventilate fully before coming back. Alternatively, you can get a spray can of starting fluid, which will accomplish a simmilar thing. It is just much less easy to control.

3) before doing either of those things, I would clean the intake as well as the throttle body, as suggested. I would also clean the MAF. I had similar problems when my MAF was starting to go. You can extend the life of the MAF somewhat with cleaning - at least that worked in my case. Although each time I cleaned the MAF it was preceded by a CEL. Therefore, I knew there was a problem and that cleaning was not going to make the MAF worse.