How reliable are engine coolent temp sensors(the blue one at back of engine). I replaced mine over a year ago cause my cossie 4x4 was missfiring when warm. Ive just noticed a few times when i first start and drive my car that sometimes the car seems to speed up without putting to much pressure on the throttle pedal. It feels like the sensor is telling the engine that its to cold and putting more fuel in. Someone said it could be a faulty ect sensor. Has anyone had the same fault before.

 

Normally very reliable, they don't tend to jump like you seem to have, they normally just go off range but, very slowly over a period of years.
tabetha

 

Had the same problem as you have in a 4x4 Sierra.
Happend wen the car was one year old. The sensor was sometimes giving 2.5 Volts when the engine was warm were it should had given 0.5 Volts or less.
Put a new sensor in and had no problems after that for 15 years.
So one sensor can die, while the other one goes on forever.

 

Its only every now and then. It feels like the car goes on its own for a few seconds then stops. Its a bit hard to explain. When i first put the new sensor in it has been running mint for months. Its only been the past few months since about september time since it has been doing it.

 

It seems that something is fluctuating, when did you last change the fuel filter ?
tabetha

 

dodgy iscv?

 

I changed the fuel filter last year about june time. This had never been changed since in all its life cause it had a date on the side which said something like 02/04/1991. I know the idle speed control valve is a bit dodgey sometimes cause the car wont idle where it soposed to idle.sometimes its ok and other times it revs at about 1200 rpm.

 

i'd try cleaning it mate. mines dodgy too but im not that bothered about it!

 

Ive had it out many a time to clean it. can cope with the revs been all over than to pay 100 quid for a new valve.

 

What is your idle CO set to ?
tabetha