tsk

I was having an intermittent problem with my temperature sensor. I'd get the occasional hard start problems. So I bought a new temperature sensor (the one in the front of the engine) and replaced it.

Now whenever I start my car cold, it hard starts and if I read the temperature off the dash it's stuck at 142 with the check engine lit up BUT only for about 2-3 minutes till the car warms up. Then it starts acting normal. If I turn off the car and restart, it's fine.

Looking around it seems like the 142 is a low voltage issue. The old sensor seemed to read fine most of the time but occasionally it did do the hard start which is why I replaced it. I don't know if I got a bad sensor but it seems odd that it would work after warming up.

Any advice is appreciated. Thanks!

Cliff Harris

What year is the car?

The CTS (Coolant Temperature Sensor) on the front of the intake manifold (or on the water pump for LT1 engines) is used by the ECM. The CTS in the cylinder head (passenger side or driver's side, depending on year) is used by the dash to indicate coolant temperature. These two CTSs do not connect together in any way. If you have a '92 or later car, the digital temperature comes from the ECM. The analog temperature comes from the CTS in the cylinder head. That might be true for '90 and '91 also, I don't know for sure.

ex-x-fire

Sounds like you installed the wrong part. Are you trying to fix a gauge issue or driveability problem.

tsk

It's a 92.

Wrong part wouldn't surprise me, but it looked identical. Amazon claimed it was the right part but I wouldn't be surprised.

Would a wrong model part take a few minutes to warm up?

It was doing the hard start thing on occasion (that's why I replaced the sensor).

Cliff Harris

I think you need to datalog to find out what the ECM is seeing from the CTS. That will tell you a lot about what is happening and why the ECM is acting the way it is.

billschroeder5842

Just go to an auto parts store and buy the correct coolant sensor. $15 bucks and swap it out. Yes, they do look similar.

It sounds like you may have gotten the wrong part. The way I understand it the coolant sensor has a WAY larger read from -40 to +250ish, and is WAY more accurate than the gauge sensor, which will only move the needle on the cluster once it reads a certain temp, which in your case sounds like 142. Makes sense that your car runs funny until it warms up--- it thinks that it is 142 when stone cold.

tsk

Just to finish this with the solution: I went to my local auto parts store and got another sensor. The new sensor was identical to the old one (near as I can tell, the number stamped on the sensor was the same). I'm fairly certain the "original" sensor I put in was just defective. New one works like a champ.

B757captain

If it's like mine (93 LT-1), the ECM sensor (water pump) connects with a 2 pin connector, the gauge sensor (RH cyl head) is a single pin. I replace my ECM sensor several times before getting a good one. Seems they are notorious for being bad out of the box. I finally got a good one from NAPA - NAPA boxing but can't remember the part number. Sensor failure will read 142 on the digital readout. Sounds like yours is not reading low temps but is reading higher. Still a bad sensor.

fake

[QUOTE=B757captain;1595723770]If it's like mine (93 LT-1), the ECM sensor (water pump) connects with a 2 pin connector, the gauge sensor (RH cyl head) is a single pin. I replace my ECM sensor several times before getting a good one. Seems they are notorious for being bad out of the box. I finally got a good one from NAPA - NAPA boxing but can't remember the part number. Sensor failure will read 142 on the digital readout. Sounds like yours is not reading low temps but is reading higher. Still a bad sensor.[/QUOTE Boil some water and place sensor probe in it but do submerge two wire pin. Attach leads from meter and read resistance then record number. After water cools test again makeing sure the electrical connectors on sensor are not touching the resistance should be diffrent if not bad sensor