mvpz

Ok all the CHTS experts

I have a 1986 n/a automatic which upon starting the
car it runs horrible it misses and an idle surges from
about 400 rpm to 750. I have to put the AC on or the lights so the
high idle circuit kicks in to keep the car running. After the temperature needle starts to move
the car smooths out and without anything on and runs great.
Also the cpu gives me a code 13. So the obviously thing was to change the CTS which I did with the
harness ( I used a Nissan original sensor) after installing nothing changed
Now the interesting thing I disconnect the harness and the car runs better but not perfect
Other then maybe a bad ECU any ideas , is there another component tied in with the CHTS
(PS MAF has been changed , plugs wires , fuel filter , distributor cap and timing set by the FM to 20")

IN ADVANCE THANKS

86tcoupe

Did you do ohms test on the spade terminals to wire the wire piercing tools is what I use
also the CHTS just runs to the gauge the Mfi temp sensor controls the ECU

rogerz

obviously 86tcoupe is drunk or on drugs as his post makes no sense and is false. you should do a continuity test from the chts back to the ecu. I usually cut off that oval connector on top of the engine and solder the wires together. did you ohm out the new connector from the chts. found out the hard way just because something is new does not mean it is good. O2 sensor is also affected by temp but probably not your problem. check the wiring back to the ecu from the chts. my buddy found someone had installed a resistor in his rig to fool the ecu.

86tcoupe

Rogers which muffler shop do you work at ? ( im channeling your replace the shocks and battery advice when a newby seeking help asks a specific ? And you slap your generic shocks ,tie rods ,and battery load test reply)
What I suggested is good first step test yes you could do what you said test the whole wire but you would also what to test most of the wires in the car and thats a huge task and not likely to happen

rogerz

someone who wrote this

Did you do ohms test on the spade terminals to wire the wire piercing tools is what I use
also the CHTS just runs to the gauge the Mfi temp sensor controls the ECU

doesn't even warrant a reply

NismoPick

lol Roger... you grumpy!

rogerz

I suffer fools badly!

mvpz

I did cut the connectors off soldered them and used shrink rap
So I'm not really sure where to go next. If there was an open wire some where in the harness the car would not react when the CHTS is connected
ANY OTHER IDEAS ??

mvpz

RogerZ
where did your buddy find the resistor would it be on the ECU board or on the harness
thanks

rogerz

added in series to the wire and hidden in the harness. did you ohm out the wires from the ecu and back at the ecu. sounds like something flaky in that circuit. OR something totally different. Kind of a guess right now. did you plug unplug the ecu connectors and check for corrosion. you are talking milliamp signals here so a little corrosion goes a long way. If you just have odd idle things going on it might be all that idle junk hanging off the left side of the plenum. it gets gunked up. took it off mine. have you checked the fuel pressure? ignition timing? I don't place a lot of faith in the ecu codes. might have been nice when things all new and shiny but after 30 years more often misdirection.
Take the schematic from the FSM down to kinkos and have them blow it up to 11x17. Much easier to read unless you are a keen eyed twenty something. get fsm at xenonzcar.com

mvpz

RogerZ
You bring up an interesting point about the milliamps that can cause the chts
not to work correctly. Do you think soldering the connection instead on the connector could cause enough resistance to cause and issue. My I should try butt connectors ???

rogerz

connectors inherently have some resistance. if corroded even more so. A well done solder joint is as close as you can get to having a zero resistance connection. as you know the wire itself has resistance so the less there is in a given circuit the better off you are. I wouldn't ***** nilly just go around soldering everything together but I have found that one connector in the chts circuit, due to its location, a questionable connection and easy enough to solder. butt connectors are even worse.

mvpz

Hey Roger
Just to eliminate all possibilities which color wire goes to the pin on the CHTS connector (PS this is my old one I have a new one ) on the side where the knotch is ? is it the yellow wire ?

mvpz

Ok
This is the connector that plugs into the CHTS what color wire is connected to the circled contact ?

Desert Rat

Based on many posts on CHTS I was under the impression that a bad CHTS reading or faulty sensor had more impact on the engine after it was up to temp than it did cold?

Mine runs rough until it's warmed up too. LIke it's getting too much fuel. CHTS and pigtail are new (timing belt just done). Had no effect. Runs wonderfully after up to temp. Will even get an occasional backfire when cold.....

Money_Pit

I'm showing up so late to this party that it's not even funny, but I'm doing this anyways. I have an 87' Turbo and I'm having the same issue. My car hates cold starts. I have found that I can play with the timing a little bit and the car will start up quickly. As it idles for the first few minutes it has some misses, but once it gets warm it runs great. Weird thing is, after a handful of starts the car progressively gets more difficult to start. Eventually I will turn it over for a few seconds with no start then turn it over again and it starts. After a few cycles of this eventually the car will really struggle to start, I'll have to press the gas pedal to give it enought juice to sluggishly start. But still once it gets going it runs. It's as of the car is self adjusting the timing and not getting enough fuel. Once a play with the timing again though this cycle starts over. I find this really weird. I have done a full tune up (plugs, wires, rotor, cap, fuel filter), I replaced the fuel pump and fpr. The only things I feel are left are the CHTS and my FTS. I am getting ready to relocate my CHTS to the driver side port of the lower intake. I'm really hoping that this will solve the bulk of my issues. I also have a messed up connector on the harness for my FTS (fuel temp sensor). I was thinking about just soldering the wires to the spade. I've heard some say that sensor does nothing for the car, but others say when their connection went bad it made the car run terrible, so we'll see. I just can't figure out why I would have to keep resetting my ignition timing to get the car to start easily. It's not like the timing is advancing or retarding. Maybe it's just me disconnecting the battery? Maybe that resets the ECU and helps with starting? I'll know more in a couple days after I replace the CHTS. If any of these posters are still listening, I'm very curious to hear your thoughts.