Just for some context, my car came with no o2 sensors installed and a high idle from the start (I suspect it's a bad throttlebody gasket). I just installed the 2 o2 sensors but the secondary I had to do the tin foil and zip tie on the shift linkage trick to try to trick the ecu (I have a test pipe so no cat), however, I noticed that the idle would now dip down from 1500rpm to 1000rpm then go back up sporadically. This didn't happen previously when I had no o2 sensors at all so I'm not sure what the problem could be. Also, does anyone have a better way of dealing with secondary o2 sensor since the CEL still ended up coming on after around 10mins of driving.

 

if you replaced the o2, why did you have to do a "hack"?
i dont know what the foil and zip tie trick is.

have you inspected other parts of the car?

I have never experienced a idle surge due to bad o2 before.

 

Ah sorry I forgot to mention but I have a test pipe, no cat, so the secondary o2 would give me a CEL. I read on another forum on HT that if u wrap the sensor in foil and keep it warm the ecu will think its functioning properly. I haven't inspected other parts of the car besides finding that if I spray carb cleaner near the bottom of the throttle body the rpms will go up which makes me think I have a vacuum leak there. However, the idle has never dipped like this before until today where I replaced the o2s. Previously, the idle was also surging but it would go up in rpm not down. Anyone know what could be the cause?