85 911 surging idle then stalls
 

hi all. the title says it! its been a few years trying to get the car to run right. just didnt have the time to mess with it. started a few years back. i replaced the fuel injectors. not factory. way to expensive!! so i forgot where i got them. but was told they were the right ones for my car. finally got them in last year. ran great for a little. then the surging idle began. it hought it was something to do with the injectors. so i starting messing with the air fuel mixture. now thats out of wack. just came across a you tube video. kind of the sam thing. surging idle. now im thinking it could be the head temperture sensor. i never replaced it. i replaced the 2 ref. sensors. it looks like the head sensor. is the top on. above the 2 ref sensors right? and it looks like it goes to the right of the fan. i actually had the car running today. just idling. i disconnected the cht sensor and the idle soared. back to my problem in the beginning. the car was running very rich. you could smell it. it was really bad. would the cht sensor be the problem. i dont want to just start replacing parts. also the icv was cleaned and working fine

I had this same problem in my 85. Did all the stuff you did. Finally took it to my super shop, they replaced the injectors with factory ones and car was fixed. So I learned, sometimes you have to pay the big bucks. I thought the after market injectors were correct also. I was told they were. My shop said no way. So , there you go.

The CHT is screwed into the backside of cylinder head on #3. If it is the one wire style (original) a very good idea to replace it. BTW, the sensor at the top is the TDC sensor, it is not used in the running of the car, nothing is connected to it.

Check for loose intake manifold nuts. Air leaks, or more accurately vacuum leaks can make your car run horrible.

And if you have your old injectors, send them in to be cleaned, and measured. If not, replace the with the expensive factory ones.

Also recommend you pull and clean the Idle Control Valve. If that is sticking you get some surging. I plan to add a AFR WBO2 sensor and gage this fall that will help ID issues with the system. There are only so many part, and there are some great go by's to sort out the issues. Take patience, which I sorely lack, but very rewarding.

Eliminate the CHT by jumping the pins in the CHT connector (white) with a paper clip.
Also sounds like you may have the wrong injectors installed.