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I've noticed that recently my car's idle has become a little unstable at times. For instance, when I come to a stop light and apply the brake, the idle will shoot up to 1 1/2 and down to around 500. It does this repeatedly until I release my foot from the brake. This also seems to happen alot at night for some reason. When going through the gears, there is no hesitation or other noticable problem. What could this be?

i have the same problem.....

Pull codes.

Check for vaccume leaks, esp in the intake boot.

Clean your TB.

If it happens @ night, could be electrical, if it only happens when the lights are on.

man I ask that before same thing here rpms goes up and down at the lights and my engine light is on come you mechanic we need an anwser for this

ty

I had that problem on my 240sx and it turned out to be a vacume leak. Just check all the lines.

I had a pretty similar problem recently.. Actually found out it was the terminals on my battery.. the negative battery terminal wasn't completely tight and i think it was over-working the system because of the weak connection..

I also had problems with my lights dimming when i used the turn signals, and when I used the AC...

Just a thought!

I suggest you disconnect the Idle Speed Control Valve electrical connector, to see whether it has any effect. If it's faulty, the idle may stabilize at the default level for 68 deg F with it disconnected. If it's not faulty, your problem lies elsewhere. Does the problem persist if you put the car in neutral while stopped? Or only in gear with the brakes on? I assume it's automatic?