coolant temp sensor bad?
 

My car is not running as strong as it once has but with seemingly good driveability & with no SES codes. It has a Performance Resource chip that turns the fan on as soon as the engine is started (cold or warm). (I wanted to put my stock chip back in for testing- comparison purposes but havent been able to find it) Thought the fan was suppose to come on when temps are near 176' or so. The temp guage on the dash always seems to read correctly. If there is another temp sensor that the ECM reads, I havent been able to locate it yet. How much does the temp sensor effect the output of the engine? I havent seen any info on this anywhere at TGO. TIA.

With the fan staying on all of the time, does it make sense to think that the sensor is reading a hot engine all of the time? -lean condition?
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89 IROC-Z 5.7L 2.77 GEARS
130,000 MILES
ALL FREE MODS
K&Ns FILTERS
FLOWMASTER MUFFLER
PERFORMANCE RESOURCE CHIP
AFPR & PORTED PLENUM
Best 1/4 E.T. 14.09 @ 97.2 MPH
Best 1/8 E.T. 9.09 @ 77.4 MPH
Best 60ft. 2.03

[This message has been edited by whiteroc (edited September 17, 2001).]

on GM cars the coolant temp sensor makes a huge difference in the way the car runs. the coolant temp senor the computer reads is in the thermostat housing. it can be checked by measuring resistance across the terminals. the temp sensor the guage reads a one wire sensor located in the drivers side head. usually when a CTS goes bad it goes real bad and the car will really run bad. it can cause a miriad of drivability problems. if you are jusd down on power with no drivability problems i would check elsewhere.

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86 IROC-Z
305 TPI
700R4 W/ shift kit
3.23 gears
T-Tops
maroon with gold stickers and rims/ black interior
43,000 miles
flowmaster exhaust, edelbrock headers, gutted airbox, converter, and MAF, K&N filters.

soon to come are 3.73 gears and subframe connecters.

Just a little more info:

On my '89 L98 the coolant temp sensor is not in the thermostat housing, its on the front of the intake manifold(passenger side).

Sparks a flyin'

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1989 L98 IROCZ, Bored .030 over,400 Crank,Dart PRO 1 Heads 200cc intake,ZZ3/ZZ4 Cam,Crane 1.6 RR,Edelbrock 3860 Hiflo TPI Manifold, AS&M LTRs, Edelbrock 58MM TB, Ported Plenum, TCI Reverse Pat Man Valve Body, SVO 24# injectors,TCI Streetfight Stall Converter, 3.23 Gears on Auburn Pro Posi, Some Suspension Mods

I thought the CTS went on my car a few years ago, did the tests and it proved to be okay. It was the computer not reading the CTS values correctly, I had to replace the ECM. Incidently, my fan would turn on when I first started the car, and it would run like crap, just like a carbed car with a badly adjusted choke. It wouldn't take the gas at all until the motor was warmed up.

Gary