coolant sensor???? idle problems ..

[89blkvet]

I have herd that the coolant sensor, if not working properly, can mess up the idle. My 89 has and idle problem, I have changed the EGR valve, EGR switch, the 02 sensor, cap and rotor, distributor module, and still idle is rough, it jumps up and down at the stop signs. Once I am running, it appears to be fine...............although I think my fuel milage is too low......12-15 avg. Any suggestions........coolant sensor or not??

 

[silver 80]

I take it that there are no codes set?
I think that is what the manual said too, but I'll have to check,

(edit) 12-15 mpg? depends on how heavy your foot is.........

 

[motorman]

have someone run a scan it is cheaper than just switching out parts.

 

[89blkvet]

How do I get the scan done ???

 

[motorman]

chevy dealer or any good repair shop can do the scan to see if the sensors are bad. cost $75/$100

 

[Top]

My coolant sensor was actually broken at the plug but you could not tell by lookin at it. The plastic part was broken off the tip of the sensor and would sometimes make contact and sometimes not. I was getting the same rough idle you were. I finally discovered it when I unplugged it to remove it to check it.

A new replacement coolant sensor cost me exactly $25.76 tax included from Vista Chevy here in Vegas.

Good luck,

 

[89blkvet]

so it does appear that the Coolant temp sensor does effect the idle, if working imporperly. heck, that could be my problem. How difficult to change?? THANKS !!

 

[Top]

To quote Haynes "Damage to ths sensor will affect the operation of the entire fuel injection system." Check to see if you have a Code 14 or 15.

Mines a Cali car so I had to move a air pump outta the way first. All told it took me about 20 minutes. Take your rad cap off to so you have no pressure in the system. Disconnect the negative cable for a bit while doing it to lose any codes. Have the new sensor all ready to go and close at hand to grab. Loosen the old one carefully and get ready, pull it and put the new one in the hole quick and you will lose minimal coolant. Put it all back, Drive a bit so the ECM relearns the new sensor is working properly and enjoy.

Let us know the outcome.

 

[89blkvet]

I will do that this weekend and let you know. THANKS !!!

 

[Edmond]

My coolant sensor was actually broken at the plug but you could not tell by lookin at it. The plastic part was broken off the tip of the sensor and would sometimes make contact and sometimes not. I was getting the same rough idle you were. I finally discovered it when I unplugged it to remove it to check it.

A new replacement coolant sensor cost me exactly $25.76 tax included from Vista Chevy here in Vegas.

Good luck,

Chris,

That would mess the idle up because the car doesn't know if it's really in open or closed loop right?

 

[Top]

Edmond,

Exactly, mine was broken/cracked about 80% of the way around. I could move it and it would break contact with the sensor. No sensor reading then the ECM thinks the engine is not hot yet, even tho' it was and keeps it in open loop, then as the engine vibrations make contact again and into closed loop it goes and on and on and on and on. The ECM is probably freakin' out with all those inputs every couple of seconds, no way it can 'learn' anything.

 

[vettered91]

How do I get the scan done ???

Hi there,

I'm sorry this can be late but here's a link that can help you to recover the ECM codes from your vette if there's any with out a scanner. All you need is a paper clip and some time!

There's some tables to see the possible causes of each code.

I hope these can help you!!

George

http://www.c4vettes.com/ecm.htm

 

[drcorvette]

Is the coolant sensor also responsible for giving you your temp reading on the dash??? And if so you said your's was broken ... did this effect your gauge on the dash???

 

[vettenick]

An open or disconnected coolant sensor will give the computer the impression that it is -40 degrees. This will not only cause the computer to stay in open loop, but it will also add fuel because it thinks the car is cold.
As a quick check, disconnect the sensor to see if the problem changes or stays the same. This will also check the computer diagnostics, because an open sensor should cause the check engine light to come on. Now, taking that into consideration, you could have a sensor that could be "off" a little. In that case, the computer will never turn on the light because it doesn't "see" anything wrong. On other thing to keep in mind is that an open thermostat could cause the same problem. Does your upper radiator hose get hot? If not, then it could be the thermostat.
Good luck!

 

[motorman]

Is the coolant sensor also responsible for giving you your temp reading on the dash??? And if so you said your's was broken ... did this effect your gauge on the dash???

the computer water temp sensor is not the same one the temp gauge shows on the dash. these computer sensor get crudded over and read incorrectly and sometimes just removing them and cleaning up the sensor with some scotch brite will do the trick. if they get crudded over they read low.