93Metro 145K,runs good. @idle, speeds up for 1 sec, and cuts gas for 1 sec. PLS help

[GMetro]

Hello friends,

I have a 93 Geo Metro at 145K miles nowadays and it has interesting problem.

Normally when i am driving it runs very good, but at idle speed it speeds up too much and if I am not touching the gas pedal, it cuts the gas and slows down for about 1 second. (I looked at the carburator to see that the engine really cut the gas to slowdown the idle.) And as it slows enough it feeds the gas and speeds up again for about 1 second. So it goes like that at idle but engine never stalls or stops. Engine Check Light is on all the time.

I am very happy about engine performance expecially after a friend of mine recomended me to use lucas oil fuel treatment.

Thanks in advance for any input.

[Crvett69]

on the side of the throttle body there is a 2 wire sensor that goes into a water passage on the tb.it tells computer when engine has warmed up. if sensor goes bad it will cause the engine to surge like that. you can run the codes to see why light is one by putting a fuse in the empty spot on fuse holder and counting the blinks to make sure but thats usually what causes the problem

[GMetro]

Thanks Crvett69, I will try changing the water temp. sensor and see what happens.

[GMetro]

Hello again, I put a jumper wire to the empty fuse hole (I did not try starting the engine when the jumper was in place). I am getting after a relatively longer blink 4 faster blinks follows and sequence repeats. Does this mean I have the error code 4?

[spy1309]

that is code 14 coolant sensor circuit like corvett69 said.

[GMetro]

Thanks to both of you. I'll get the part and try to replace it.