Idle Confusion
 

I have had this car for a while now and since i got it the motor was idling high. 1800 to 1950. The idle goes up and down. Like it has a big ported motor but i t doesn't. I was able to bring the idle down to 1100 to 1250 where it just jumps up and down lol. I was told that im not able to adjust the idle where it should be or get it to run smooth since it doesnt have and o2 sensor. The car has a custom Downpipe that did not include the o2. Yeah the car runs RICH! it will burn out a new Cat in 2 1/2 weeks tops.


87 TII

Look in the 2nd gen FAQ page for 'setting the TPS'

Get an aftermarket down pipe with an O2 sensor bung.

well I did adjust the TPS i even made my own jumper for the green connector. but the lowest that the idle got to was where it is now.

I was thinking about the aftermakerket down pipe with the o2 bung adapter but I Dont want to go through the hassle of removing cutting and rewelding my exhaust system. I was thinking about drilling into the downpipe the car has right now and just getting a Nut to hold the o2 welded on. Wouldn't that be a simpler solution? Oh yeah and where does the o2 sensor go connected? I dont have a clue there are no unplugged wires that i see. Could someone post a pic of where it should be or guide me to a thread with that info?

Well Thanks everyone

Aha Success!

Please explain how you fixed this problem so that other members who use the search function can find this thread and have the info be beneficial to them.

The O2 sensor on the S4 is a dumb, on/off, sensor. It's primary purpose is AFR adjustment while on cruise control for fuel mileage. Ignore the person who feed you the BS you posted on your first post. My guess is you don't have the air pump functional, that's why cats are so short lived, along with the fact that the cat needs to be designed for rotary heat.

The FC ecus are basically dumb, meaning they can't be manually adjusted for AFRs. The high idle and hunting indicate a potential vacuum leak and a BAC that needs cleaning.

The stock O2 wire plugs into a single wire green connector that's usually hidden under the rats nest at the top/rear of the engine. Download the FSM from the link in my sig line and check the wiring diagram.
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