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1G Idle Position Switch and CEL only at idle


Proven Member
Jan 20, 2015
SoCal, California
Hi guys, I've been researching this check engine light issue I'm having but can't get it sorted out, hopefully you can help.

I'm working on my brother's 1g gst and his check engine light comes on only when the car is at idle, however the car idles perfectly. The second you give it any gas the light goes away until the revs come back down to idle and then the cel illuminates again.

If i remove the connector on the idle position switch the cel goes away but the car searches for idle and can't find it so it's all over the place (surging 500rpms-2000rpms). If I pull the idle position switch out and put my finger over the tip of the sensor then the cel comes on, if I take my finger off then cel goes away (this is with the car in the on position).

I've tried adjusting the ips but there are only two options, it's tightened down and I get a cel or it's too loose and the car can't find idle. Any ideas? Thanks everyone!
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