map sensor only and fuel trims for air leak detection

have a car with just a map sensor and no maf.Im suspecting airleaks .I understand using fuel trims for airleak detection is a powerfull method.With just a map sensor ive read its a different set of rules compared to using a maf.Any body have some light to shed on fuel trims and map sensor for air leaks etc cheers ian

MAP only engines tend to be very tolerant of vacuum leaks which can make diagnosis more difficult as often the only symptom is a slightly raised idle speed. The usually methods are either water spraying or propane while listening to engine note and watching RPM and STF but smoke testing the intake and also an ultra sonic leak detector can be useful.

definitely have airleaks that respond to carb cleaner being sprayed around,and stft is schizophrenic so much that using propane is hard to detect any meaningfull change.The manifold is a dire plastic unit so the leaks i think could be either on a seam or a crack in the main body

Sometimes inside knowledge on an engine type can be a help --- some engine types example Rover K4 the plastic inlet mainfold is known to give gasket issues on cylinders 1 or 4 this can often be shown by shaking the manifold but on the Rover KV6 is prone to the seam joints splitting. With Fords the prime suspect is always hoses and connections to the manifold. One old school trick was to use an old school pump oil can with a fairly viscous oil and dribble this along suspected joints. On non-drive by wire engines disconnecting the idle speed control valve can help to make any change in idle speed more obvious.

An air leak on a MAP engine will affect the MAP value itself and result in a higher than normal reading at idle. How is yours?

The fuel trim with an air leak will, generally, not be affected that much. This because the ecm already considers the higher manifold pressure in its calculation. What kind of fuel trim correction do you actually see?

If this car has an IAC valve: what's it's position or % reading?