Fluctuating Idle

[NICONick]

OK so recently when I am stopped at a red light for an extended period of time my idle begins to fluctuate and the car almost wants to stall. Then I tap the gas and it stays at idle and then starts to dip again, about every 60-90 secs of idling is when it will start to fluctuate and sometimes goes below 500 and almost dies...

Any clue?

[Klits562]

OK so recently when I am stopped at a red light for an extended period of time my idle begins to fluctuate and the car almost wants to stall. Then I tap the gas and it stays at idle and then starts to dip again, about every 60-90 secs of idling is when it will start to fluctuate and sometimes goes below 500 and almost dies...

Any clue?

i had the same problem mine was caused by vacuum leak, the only thing is finding the leak.
check your intake piping especially around your maf and check your brake booster and all lines that from the booster to intake mani.

[94_240sx]

Try this too. Spray carb cleaner to throttle body and ICV. I had similar problem, but fixed after that.

[CRyan]

Vacuum leak vote here, also.

Its not TOO hard to find a vacuum leak, take a bottle of throttle body cleaner and have the engine running as you spray all your vacuum lines, when you hear the engine surge up in the RPM, start looking for your leak in that area.

[NICONick]

Vacuum leak vote here, also.

Its not TOO hard to find a vacuum leak, take a bottle of throttle body cleaner and have the engine running as you spray all your vacuum lines, when you hear the engine surge up in the RPM, start looking for your leak in that area.

If it were a vacuum leak tho wouldn't the problem be constant? Not after sitting for a little at idle? I could be wrong but...? Yes? No?

[CRyan]

That all depends what the leak is near, good sir. If its far down a vacuum line, not close to any kind of sensors or devices, it would be a constant thing. But you have to remember, all the sensors/modules on the engine are always sending information to your ECU. Keeping that in mind, the ECU is always making slight adjustments to make sure the engine maintains normal RPM, etc. If it is thrown for a loop and has air coming in from somewhere before or after, another sensor/module will pick it up and say "fix here", as the other one before the leak says "its ok." So a fluctuation is normally the finger point to vacuum leaks.

[CRyan]

Oh, and BTW, when the car is further in the RPM, air becomes something it needs, at idle it is voluntary to adjust accordingly. . .if that makes sense. So no, just because the car doesn't act stupid through its RPM, doesn't mean that it isn't a vacuum leak.

[OutToWinPAHC]

could also be a bad flakey IAC, MAF, o2 sensor, or TPS

[NICONick]

Yeah first thing Im going to do is try to clean my IACV and MAF and see if that helps at all...

[deadmongoose]

Nick, did you find what caused it? Mine is doing the same thing. I'm going to check the vacuum lines first and go from there, I just wanted to see what you ended up doing that worked.