Brian's long post all about engine management (which I found very educational) got me thinking about the MAP sensor.
I didn't have a clue what it stood for (Manifold Absolute Pressure) so I did some searching.

I found the following for those who want to know a bit more about the various types of sensors used with fuel injection systems.

Toyota document

From the rather good \"How Stuff Works\" guide to fuel injection

Motorola

The How Stuff Works site is excellent if you haven't seen it before. Really useful for settling pub arguments about things like how fluorescent tube starters work...

I'm wondering why banging a dicky MAP sensor makes a difference. The actual sensor element is a semiconductor like this one.

I'd have thought the problems would normally be due to either poor electrical contacts, or poor vacuum coupling.

Any ideas?

 

It's thought to be oil contamination, coming from the PCV system. Tapping it, is hopefully displacing any contamination to keep it all open to the intake, giving an accurate reading.

A few people have thought about remote mounting the Map sensor - you'd just need a takeoff plate, and some vacuum tubing to connect the sensor. Honda used to do this on some older Hondas (Have a look round the different cars at a show.). The S2000 isn't the first one with the map sensor in the throttle body though - the ITR for one had similar placement. It could just be some quirk of the intake manifold's behaviour with different flows.

-Brian.

 

tap it...