Warm Idle is 1800 rpm

[epbrown]

The idole on my car has been 1200 rpm at cold start, dropping to 800 or 900 after the car warms up. I recently had cause to replace the battery and ever since the car's started at 1200 rpm cold and gone up to 1800 rpm. Searching the archives, I find it unlikely installing a new battery is the cause; I suspect that I accidentally changed something while I was in there - knocked a hose loose or whatever. Any idea what I could have done? Is there anything that could have affected the idle that's near the battery area. I'm too unfamiliar with the engine bay to spot anything right off, like I would with my 911.

Emanuel

[SoCal Driver]

Few vacuum hoses in the battery compartment.

But it does sound like you have a vacuum leak. The idle control valve in the early 944's is a heated spring affair. The bi-metalic spring closes off the bleed from the "outside" of the throttle to the intake side. Uses a sliding plate or knife valve design. It's not uncommon for this to become crudded up and stick open. It's under the middle of the intake mounted on the block.

Another point where the vacuum manifold can leak is at the brake booster fitting or the other fittings in that area. This is opposite the battery. Follow the large hoses back to the manifold and check for cracking.

[Porsche944]

Check the vacuum line to the vacuum tank which is located in the battery box.