Okay, so my car has been getting steadily worse and worse at cold running. Low idle, low vaccuum, bucking, hesistating, and almost stalling. As soon as it reaches operating temp, it runs/idles great though.

I replaced the engine coolant sensor with a brand new one in the spring, but it only helped for a short while. I do not want to buy coolant temp sensors (or install them, they're a pain) every few months.

So I found this:
http://img.photobucket.com/albums/v465/djgeorge2k/fsm1.jpg

And decided to test my sensor. Turns out my resistance was way, way low, which was a suprise to me. This causes the ECU to think the engine is warmer than it is, causing a very lean condition, causing the poor running. The sensor gets gradually closer to spec as temp rises, which explains why it runs fine warm.

So what I did was wire in a Radio Shack SPDT switch and resistor in series into the circuit to bump up the resistance at cold to where it's supposed to be. I then flip the switch off as soon as the car starts to warm up to go back to the stock signal.

Ghetto, but worked like a charm this morning. If anyone has any insight, better ideas, or wants more detailed info, let me know.

Sounds like you got the wrong sensor for your car.

C

You probably bought the B13 sensor. PM me if you want the B14 one, as i have a brand new OEM one.

Sounds like you got the wrong sensor for your car.

C

bingo

Should be the right sensor. It's the blue B14 one, direct from the dealer. The red b13 one doesn't plug into the b14 harness.

The ran great for around a year on the old sensor, then took a dump. It ran great on this sensor for around a month before it started going bad.

You do agree then, that the new sensor has gone bad, you tested it yourself, no? Though I don't know how they're going bad. Maybe just bad luck.

C

bad wire gong to the sensor??? +1 on the bad luck

would a bad sensor cause it to not restart once its has come to running temp!?

would a bad sensor cause it to not restart once its has come to running temp!?

I would like to bring this thread up from the dead. I have a B14 JWT ECU for U12, 50lbs inj., Z32. I can start the car fine, well actually with a bit of turning over, and the afr on my wideband stays around high 15's to low 16's..then as the temp goes up it leans 18+ afr and the car sounds like its on cams. Is this due to the coolant temp sensor? I have the blue B14 coolant sensor as B13 would not fit the harness. So I am actually having the opposite reaction than the creator of this thread. How can I check if it is indeed the coolant temp sensor? Also during idle the temperature is around 210 F according to my datascanner.

Just fyi, on the B13 red connector, it is 2.3k around room temp, so I would imagine the RTD's are similar.

Just fyi, on the B13 red connector, it is 2.3k around room temp, so I would imagine the RTD's are similar.

anyone else?

i have this same problem on my 93 se-r which has mods but no jwt ecu. also have the same prob, but worse on my 93 ga16 which has cams, ecu, etc. i've replaced coolant temp sensors and all but my prob. (cold idle warm up) remains. atleast he fixed his prob. ghetto it may seem, but worked. i do think there is something else causing this, not 100% convinced it is the coolant temp. sensor alone eventhough this usually is the culperate.

Do you have an IACV-Regulator? Is your IACV-ACC operating? The IACV-Regulator allows more air in when it's cold so you should idle pretty high when you first start your car (around 1200-1300 RPMs). When it warms up (about 5 mintues or so), it should start going down until it reaches your normal idle RPM.

The IACV-ACC just keeps your idle as close to possible to the set idle speed (750-800 RPMs).

I am having the same issues, I think I might replace this sensor. There cheap aren't they??