Air Flow Position Sensor

[89-300ce]

My M103 has a rock steady idle when cold but when hot in closed loop has a hunting idle. It's not bad but anything short of perfect just seems so out of place on these cars.

I've read the threads on Air Flow Position sensor replacement and suspect this may be what I need. I put an ohm meter on pin 1 to 2 and then 2 to 3 and whatched the readings as I moved the air flow plate. My readings seem to go down with the first bit of movement of the plate and then begin to move steadily up. Does this first drop of resistance indicate a bad air flow position sensor?


Thanks

[sbourg]

Ohmmeter is not a good tool to test this pot. Use a voltmeter,
with engine and connector off, attach a battery (D.C. source) across 1 & 3 and measure between 2 & either 1 or 3 while moving the meter air vane. At rest the voltage should be low, and increase smoothly as the vane is pushed slowly open.

If the pot is bad and you replace it, calibration of the new pot is checked with voltmeter probing the pot with connector on, engine at idle.

Steve

[89-300ce]

Thank you.

This forum is great!

[89-300ce]

Well, my pot checked out OK. Any idea of the mileage when they typicaly are suspect?

I think I may have solved my idle issue. I was tracking down why my seat belt presenters didn't work. One side the module didn't work and I opened it and replaced a corroded spring and contacts to get it working. The other side was traced to seat belt switch conatcts not opening. When I removed the seat to fix the seat belt switch I noticed the vacuum line to my seat back locks that had become disconnected.

So with one repair I fixed my seat belt presenters, my seat back locks and my hunting idle. I'm on a roll!

PS. I've worked on a lot of cars in my life but the fit and finish of these Merc pieces are a true joy. Things just fit.