Thread: help please
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Old 04-25-2003, 05:04 PM
UKEvo UKEvo is offline
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Join Date: Mar 2003
Posts: 64
Hi Martin,

I'm not saying it's definitely the problem, just something to check - fingers crossed tho! Hesitation could be caused by many things such as fuel pressure, injectors, ignition etc.

I wouldn't worry about the pot readings specifically. Set your meter up to 20K ohmns scale and read pins 1-2 (from memory). I'm not sure on the 560 but you'll probably have a short harness that runs from the actual pot on the AFM to a main wiring harness connector located to the side of the fuel metering head/distributor. You can simply remove the connector plug and test the resistance values here, much more accessible than directly at the pot - well at least on my 16V the pot itself is virtually inaccessible under the intake manifold. So long as you have continuity in that short harness you'll be sweet. Don't need power to the unit to measure resistance.

Depressing the AFM plate, on mine I see 1K approx at zero position through idle period until I hit the control plunger then the values start to rise. If you can see a increase in resistance, no dropping out etc, no going infinity then at least the potentiometer is working to some degree. Finding the actual values might be very difficult, I couldn't even find them in the actual Bosch literature for my AFM, but I found a voltage chart instead. Be aware that the pot is not just for idle but also for running and if it's not working properly then you will get hesitation at cruise etc like I had. The worst thing about mine was the constant stalling, especially when turning, and the pyschotic idle 500-1500, 500-1500 ad infinitum!! LOL

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