i just finished reading some posts invloving a coolant sensor. i feel odd asking, but where is that?? recently i failed emissions pretty bad and have had a weird idle, so i figured i may be bordering on limp home mode. now, my car seems to be running at normal power, but every now and then i have a doubt. i was wondering if possibly this sensor could be the problem. one more thing...if this sensor was going to poop out, would it definately bring up a code, because i have not gotten any service engine lights. thanks in advance.

 

ok, this is a lot of stuff all at once...

The coolant temp sensor is located in the front of the intake manifold. It has a two wire plug running into it and you'll notice that its probably by the thermostat housing on the intake.

What it does is tell the computer what the engine temperature is, it works sort of like your thermastat, or more like the coolant temp sending unit (the thing that runs your gauge).

I suppose that if the sensor is bad it could inhibit the car from entering closed loop and running with poor emissions. This doesn't really seem to be your problem though. This sensor barely ever fails. It probably wouldn't trip a ses light though.

You might want to look into either your knock module, sensor, or the O2 sensor.

-=-Mike

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1989 RS.. 355, Hypereutectic pistons, double roller cam, double roller timing chain, accel wires, blue streak cap and rotor, rapidfire plugs, chevy caprice 350 chip, 200* fan switch, 3 angle valve job, 3 inch cat-back exhaust, 3 core radiator, 3.73 gearing with POSI.

 

Temp sensors do fail, and if they do, they can cause multiple problems, including hard starting, rough idle, overheating, etc. A lot of times they won't trip the SES light. When my sensor went bad I only noticed it because my torque converter wasn't locking up on the highway. When I put a scanner on it I watched the sensor temp reading jump from 180 to 220 then back to 160 within a few seconds, all the while the temp on the car (read by the gauge which was accurate) was going up up up, with no cooling fan coming on. I guess the computer didn't catch it because it's possible for quick temp changes with the thermostat opening and closing. Anyway, in order for the computer to catch a failed sensor, it has to fail pretty bad. Like if the computer sees that the temp is at -100 or 500 degrees or something crazy like that, it will know something is wrong. If instead the temp reads at 100 when it's really 200, then the computer won't detect the problem, it'll just run bad.
BTW what engine do you have, and what year?

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91 Z28
Come see The Vicious...

 

RS,

If you know the approximate coolant temperature, you can test your CTS without removing it from the engine. Read the resistance across the two terminals (or the terminal and ground) and compare it to the table:



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Later,
Vader
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If you want to beat the World, it might reach up and pull you down...
Adobe Acrobat Reader

 

Thanks for the input guys. I actually have replaced the coolant sensor just for the heck of it a few months ago (i just didnt realize it was a sensor...just thought it was a temp "gauge". Anyway...she is still not pulling as best she can. I know my car, this is not in my mind. I get no SES readings at all, and I replaced all the little things...plugs, wires, rotor, cap, coil, oil, filters, freeze, even a new cat!!!and still...the car will get high into gear and its almost as if the engine slows down (which led me to think "limp home"). I even filled my tires thinking i was dragging a bit, but no. Could it possibly be the timing? or how about this...alternator? Btw, I have a 91 305 tbi. Thanks in advance.