MAF sensor problem?

[hpaulb]

How do i test my maf sensor. Have been having surge problems for some time. Stored for the winter so haven't looked at it for months. Started out small. Rough idle then some surging. Got worse last fall . Now it either runs at 2k or dies at idle. Have a second engine for parts so have been swapping out parts to no avail. Ne wires, cap, injectors, splugs ox sensor. Have idle valve but haven't swapped it out yet. Tests ok electrically and no difference unplugged? swapped throttle body to. Compression at 165 all cylinders. Don't have a spare maf sensor.

[v2rocket_aka944]

unplug the idle valve and try starting it with the throttle cracked open by hand/foot a little.

[DannoXYZ]

Most likely intake leak in hoses & clamps between AFM and intake valves. Inspect, as in take apart, every single hose and clamp and look for breaks and cracks.

To test AFM, measure output voltage at DME connector at:

1. Idle with warmed up engine
2. 3000rpms steady speed in 3rd gear (45mph)

Leaks will cause air to go into engine without being measured by AFM. Leading to lean mixtures and stumbling.

DO NOT swap parts without testing first. How would you know that the replacement part isn't bad also? How would you know that you didn't introduce some secondary issue in the swap process? Like causing an intake-leak or cracked some old crispy wiring?

[Westy]

The easiest thing to do is buy a spray can of MAF sensor cleaner and spray the 'dust' off the sensor. On my 911, it was hunting, so I used a can of brake cleaner and started spraying at all the fuel intake areas to see when the idle changed/surged. That's the best way to see if there's an air leak somewhere. If those 2 things don't work, then yeah, it's some electrical gizmo which I know squat about.

[hpaulb]

OK, next i'll take the intake manifold off and inspect further.

[djnolan]

Before you do that run a smoke test...