Surging when stopped

[riversidedan]

so I just had the CTS replaced in my 92 and after they did the job showed me the scan screen and said it looked a lot better. But when drivng and will come to a light or a stop and the car wants to pulsate like it wants to move , but if I shift to neutral itll idle smooth, the car also runs smooth going down the road, its just when Im ata light and In
gear the pulsating occurs, BTW its an AUTOMATIC.....thanx for your input.

 

[LLC5]

so I just had the CTS replaced in my 92 and after they did the job showed me the scan screen and said it looked a lot better. But when drivng and will come to a light or a stop and the car wants to pulsate like it wants to move , but if I shift to neutral itll idle smooth, the car also runs smooth going down the road, its just when Im ata light and In
gear the pulsating occurs, BTW its an AUTOMATIC.....thanx for your input.

Are the rpm's surging up and down at the same time when you are at an idle and stopped, and if so what are the idle rpm's range? Do the surges have the same time delay between them, or are they random?

Why was the CTS (coolant temp switch I am assuming?) replaced?

 

[riversidedan]

to my knowledge the surges are even when in gear at a stop light, but when in neutral and stopped it runs smooth............. when I had the car inspection done they did note the CTS needed replacing. and per above I saw the scan reading b4 and after the CTS was replaced and their was a difference....so let me ask what do you think the problem could be?

 

[LLC5]

to my knowledge the surges are even when in gear at a stop light, but when in neutral and stopped it runs smooth............. when I had the car inspection done they did note the CTS needed replacing. and per above I saw the scan reading b4 and after the CTS was replaced and their was a difference....so let me ask what do you think the problem could be?

The answer to why the CTS was replaced still isn't clear, but did this issue happen after the new CTS or was it there before the new CTS. What are the rpm's when it surges, the lowest rpm and highest rpm?

A steady timed surging normally suggests a vacuum leak/air fuel mixture issue, a random surge generally indicates a electrical or mechanical issue. Keep in mind the word "GENERALLY" as this would only be a guide line to follow. I would check all your vacuum lines, and air filter to throttle body tubes and clamps for loose fitment first and see if there are any stored trouble codes. Good luck with it.