85 turbo - idle going crazy

Idle speed keeps fluctuating for no reason, way overspeeding sometimes. Tried swapping in a new throttle position sensor as this worked on another one of these cars I had once, no change. Also when car is doing this when first cold, the speedometer starts reading off random numbers (??) but this seems to go away shortly. Am not getting any power loss light nor any stored codes. It definitely seems to be the computer telling the idle motor to increase erratically - if I unplug the idle motor, idle stays steady forever until I plug it back in, in fact I'm driving it like this now. It seems to vary between normal and various overspeeding, it is not making it go too low (not stalling). Any suggestion on what to check or change next? Could it be either of the sensors in the distributor? I changed the rotor but thats it. thanks!...Mark

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mark french
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Before I spend $ on the speed sensor...if I unplug the reference pickup, the idle drops to a steady level. Plug it back in and idle jumps back up and starts hunting up and down again. Does this indicate the problem might actually be that pickup? thanks! Mark

Reply to
frenchy

Correction, I am unplugging the sync pickup, not the reference.

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frenchy

AFter changing the distributor pickup I think the problem turned out to be some crud in the throttle body plate and/or orifices. I had scrubbed it while back but apparently some more must have built up. Idle must have been simply adjusting to fact the crud was built up in that area. Cleaned it and idle is steady as a rock now....Frenchy

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frenchy

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